Clinical Approach to Vomiting

Pediatric Comprehensive Framework

1
Symptom Overview
Overview
2
Pathophysiology
Mechanism
3
History Taking
History
4
Physical Examination
Examination
5
Differential Diagnosis
Differential
6
Investigations
Workup
7
Clinical Decision-Making
Algorithm
8
Pearls and Pitfalls
Summary

1. Symptom Overview

Understanding the clinical significance and classification of vomiting in children

Vomiting is one of the most common symptoms encountered in pediatric practice, accounting for approximately 10% of all pediatric emergency department visits. It affects children of all ages, from neonates to adolescents, with the highest incidence occurring in infants and young children. Acute gastroenteritis alone causes over 1.5 million outpatient visits and 200,000 hospitalizations annually in children under 5 years in the United States. Understanding the approach to vomiting is essential because while most cases are self-limiting viral illnesses, vomiting can also be the presenting symptom of life-threatening conditions requiring urgent intervention.

Definition

Vomiting is the forceful expulsion of gastric contents through the mouth, involving a complex coordinated reflex with contraction of abdominal muscles, relaxation of the gastroesophageal sphincter, and retrograde peristalsis. It must be distinguished from regurgitation (passive return of gastric contents without effort), rumination (voluntary regurgitation and rechewing), and posseting (small effortless vomits in infants that are physiologically normal).

Key Epidemiology

10% of pediatric emergency visits
50% of infants have regurgitation
1.5 million outpatient visits annually for gastroenteritis

Peak age: 6 months to 2 years
Dehydration risk: highest in infants
Surgical causes: 5-10% of acute cases

Classification by Duration

Category	Duration	Common Causes	Clinical Significance
Acute	Less than 7 days	Acute gastroenteritis, otitis media, urinary tract infection, appendicitis, intussusception	Most common presentation; focus on hydration status and ruling out surgical emergencies
Chronic	Greater than 7 days	Gastroesophageal reflux disease, food allergy, peptic ulcer disease, cyclic vomiting syndrome	Requires systematic evaluation; consider gastrointestinal, neurological, and metabolic causes
Recurrent/Cyclic	Episodic pattern with symptom-free intervals	Cyclic vomiting syndrome, abdominal migraine, metabolic disorders	Characteristic stereotypical episodes; often associated with migraine family history

Classification by Character

Non-Bilious Vomiting

Appearance: Clear, white, or containing partially digested food or milk

Significance: Obstruction proximal to the ampulla of Vater, or non-obstructive causes. Most common type in children.

Common causes: Gastroenteritis, gastroesophageal reflux, pyloric stenosis, overfeeding, food intolerance

Bilious Vomiting

Appearance: Green or yellow-green color indicating bile

Significance: RED FLAG – suggests obstruction distal to the ampulla of Vater until proven otherwise

Common causes: Malrotation with volvulus, intestinal atresia, incarcerated hernia, intussusception

Critical Point: Bilious Vomiting in Neonates

Bilious vomiting in a neonate is a surgical emergency until proven otherwise. Malrotation with midgut volvulus must be excluded urgently as bowel necrosis can occur within hours. Immediate surgical consultation and upper gastrointestinal contrast study are required.

Classification by Pattern and Timing

Pattern	Description	Suggests
Projectile	Forceful vomiting that travels a distance; infant remains hungry immediately after	Pyloric stenosis (classically in 3-6 week old infants)
Post-prandial (immediately after feeds)	Vomiting occurs during or immediately after feeding	Gastroesophageal reflux, overfeeding, milk protein allergy, pyloric stenosis
Early morning	Vomiting on waking, often without nausea	Raised intracranial pressure, posterior fossa tumors
Associated with feeding changes	Onset coincides with introduction of new foods	Food allergy, food protein-induced enterocolitis syndrome
Cyclic/Episodic	Stereotypical episodes of intense vomiting with symptom-free intervals	Cyclic vomiting syndrome, abdominal migraine, metabolic disorders
Associated with specific triggers	Vomiting occurs with motion, stress, or specific activities	Motion sickness, psychogenic vomiting, post-tussive vomiting
Bloody (hematemesis)	Fresh blood or coffee-ground appearance	Mallory-Weiss tear, peptic ulcer, esophagitis, swallowed maternal blood (neonates)
Feculent	Fecal odor to vomitus	Distal bowel obstruction, gastrocolic fistula

Age-Specific Considerations

Age Group	Common Causes	Key Considerations
Neonate (0-28 days)	Overfeeding, gastroesophageal reflux, pyloric stenosis (late), intestinal atresia, malrotation, necrotizing enterocolitis, inborn errors of metabolism, sepsis	Bilious vomiting is always pathological; lower threshold for sepsis workup; consider congenital anomalies
Infant (1-12 months)	Gastroesophageal reflux, acute gastroenteritis, pyloric stenosis (3-6 weeks), intussusception (6-36 months), food allergy, urinary tract infection	High risk for dehydration; pyloric stenosis peak age; intussusception most common 6-36 months
Toddler (1-3 years)	Acute gastroenteritis, intussusception, ingestion/poisoning, otitis media, urinary tract infection, appendicitis	Ingestion history important; intussusception still possible; appendicitis presents atypically
School-age (3-12 years)	Acute gastroenteritis, appendicitis, migraine/cyclic vomiting syndrome, streptococcal pharyngitis, diabetic ketoacidosis	Appendicitis more classic presentation; consider cyclic vomiting syndrome; diabetic ketoacidosis may present with vomiting
Adolescent (12-18 years)	Acute gastroenteritis, appendicitis, pregnancy, eating disorders, migraine, diabetic ketoacidosis, substance use	Pregnancy test in all females; consider eating disorders and substance use; more similar to adult causes

Key Concept: The Age-Based Approach

The differential diagnosis for vomiting varies dramatically by age. In neonates, always consider congenital anomalies, sepsis, and metabolic disorders. In infants aged 3-6 weeks, pyloric stenosis is a key consideration. In children aged 6 months to 3 years, intussusception must be considered. In school-age children and adolescents, the causes become more similar to adults, but pregnancy, eating disorders, and substance use must also be considered in adolescents.

Impact on the Child and Family

Vomiting significantly impacts both the child and family. Acute vomiting can rapidly lead to dehydration, especially in infants and young children who have higher fluid requirements relative to body weight and limited physiological reserves. Chronic vomiting can result in failure to thrive, nutritional deficiencies, dental erosion, and significant caregiver burden. The psychological impact on families includes anxiety, missed work or school, and disruption of family routines. Understanding these impacts helps guide management decisions and family counseling.

2. Pathophysiology and Mechanisms

Understanding the underlying mechanisms of vomiting in children

Vomiting is a highly coordinated reflex designed to protect the body from ingested toxins and noxious substances. Understanding the vomiting reflex arc and the various pathways that can trigger it is essential for determining the underlying cause and selecting appropriate antiemetic therapy. In children, the immaturity of certain components of this system and age-specific anatomical differences affect how vomiting presents and which conditions are most likely at different ages.

The Vomiting Reflex Arc

Component	Structure	Function
Receptors	Gastrointestinal tract (vagal afferents), chemoreceptor trigger zone, vestibular system, higher cortical centers	Detect mechanical distension, chemical irritants, toxins in blood, motion, and psychological stimuli
Afferent Pathway	Vagus nerve (cranial nerve X), glossopharyngeal nerve (cranial nerve IX), vestibular nerve (cranial nerve VIII), splanchnic nerves	Transmit signals from peripheral receptors to the vomiting center in the medulla
Integration Center	Vomiting center in the medulla oblongata (nucleus tractus solitarius and surrounding reticular formation)	Integrates all afferent inputs and coordinates the vomiting response when threshold is reached
Efferent Pathway	Vagus nerve, phrenic nerve (C3-C5), spinal nerves to abdominal muscles	Coordinate the motor response including glottic closure, diaphragm contraction, and abdominal muscle contraction
Effectors	Diaphragm, abdominal wall muscles, gastroesophageal sphincter, gastric smooth muscle, glottis, soft palate	Execute the coordinated expulsion of gastric contents while protecting the airway

Input Pathways to the Vomiting Center

Chemoreceptor Trigger Zone

Location: Area postrema in the floor of the fourth ventricle

Key feature: Located outside the blood-brain barrier, allowing detection of circulating toxins and drugs

Receptors: Dopamine (D2), serotonin (5-HT3), neurokinin-1 (NK1), opioid receptors

Triggered by: Medications (chemotherapy, opioids, digoxin), uremia, metabolic disturbances, ketoacidosis, toxins

Gastrointestinal Tract

Receptors: Mechanoreceptors (distension), chemoreceptors (irritants, toxins), 5-HT3 receptors on vagal afferents

Afferent pathway: Vagus nerve (primary), splanchnic nerves

Triggered by: Gastric distension, mucosal irritation, infection, obstruction, inflammation, ischemia

Vestibular System

Location: Inner ear vestibular apparatus

Pathway: Vestibular nuclei to vomiting center via histamine (H1) and acetylcholine (muscarinic) pathways

Triggered by: Motion sickness, labyrinthitis, vestibular neuritis, Meniere disease, posterior fossa lesions

Higher Cortical Centers

Location: Cerebral cortex, limbic system

Pathways: Direct connections to vomiting center, likely involving multiple neurotransmitters

Triggered by: Anticipatory nausea, anxiety, unpleasant sights/smells/tastes, raised intracranial pressure, pain

Phases of Vomiting

Phase	What Happens	Clinical Relevance
Pre-ejection (Prodromal)	Nausea, salivation, pallor, sweating, tachycardia, relaxation of proximal stomach, retrograde giant contractions in small intestine	May be absent in infants; provides warning in older children; autonomic symptoms help distinguish from regurgitation
Retching	Rhythmic contractions of abdominal muscles against a closed glottis with descent of the diaphragm; gastroesophageal sphincter remains closed initially	Generates the pressure needed for expulsion; may be prolonged and distressing
Ejection (Expulsive)	Sustained contraction of abdominal muscles, relaxation of gastroesophageal sphincter, elevation of soft palate, closure of glottis, expulsion of gastric contents	Forceful nature distinguishes from regurgitation; airway protection mechanisms may be immature in neonates
Post-ejection	Return of normal gastric motility, potential continued nausea, fatigue	Resolution of nausea varies; persistent nausea suggests ongoing trigger

Mechanisms by Condition

Condition	Mechanism	Clinical Implication
Acute Gastroenteritis	Enterotoxins stimulate 5-HT3 receptors on vagal afferents; mucosal inflammation activates mechanoreceptors and chemoreceptors; toxins absorbed into bloodstream stimulate chemoreceptor trigger zone	Ondansetron (5-HT3 antagonist) effective; supports oral rehydration by reducing vomiting
Pyloric Stenosis	Hypertrophy of pyloric muscle causes gastric outlet obstruction; gastric distension activates vagal mechanoreceptors; projectile vomiting develops as obstruction worsens	Non-bilious (obstruction proximal to ampulla); metabolic alkalosis from loss of gastric acid; surgical pyloromyotomy is curative
Intussusception	Bowel obstruction causes distension proximal to intussusceptum; venous and lymphatic congestion leads to edema and ischemia; severe pain triggers vagal response	Initially non-bilious, becomes bilious as obstruction progresses; associated with colicky abdominal pain and “currant jelly” stool
Malrotation with Volvulus	Midgut twists around the superior mesenteric artery; causes complete or partial obstruction and bowel ischemia; rapid progression to necrosis if untreated	Bilious vomiting is the cardinal sign; surgical emergency; can progress to shock and death within hours
Gastroesophageal Reflux Disease	Transient lower esophageal sphincter relaxation allows gastric contents to reflux; esophageal irritation and distension trigger vagal afferents	Distinguished from physiological reflux by associated symptoms (poor weight gain, irritability, respiratory symptoms); responds to acid suppression
Raised Intracranial Pressure	Direct pressure effect on vomiting center in medulla; may occur without nausea; often worse in morning due to recumbent position and CO2 retention during sleep	Early morning vomiting without nausea is classic; may have headache, papilledema, cranial nerve palsies; urgent neuroimaging required
Cyclic Vomiting Syndrome	Likely involves mitochondrial dysfunction, dysregulation of hypothalamic-pituitary-adrenal axis, and altered autonomic nervous system function; related to migraine pathophysiology	Stereotypical episodes; often family history of migraine; may respond to migraine prophylaxis; supportive care during episodes
Metabolic Disorders	Accumulation of toxic metabolites (such as ammonia in urea cycle defects, organic acids) stimulate chemoreceptor trigger zone; may also cause encephalopathy affecting vomiting center	Consider in neonates with vomiting and lethargy, poor feeding, or altered consciousness; urgent metabolic workup needed
Food Protein-Induced Enterocolitis Syndrome	Non-IgE mediated immune response to food proteins causes intestinal inflammation; increased intestinal permeability; fluid shifts into gut lumen	Profuse vomiting 1-4 hours after ingesting trigger food (commonly cow’s milk, soy); can cause shock-like state; removal of trigger is curative
Appendicitis	Visceral afferent stimulation from inflamed appendix; referred pain mechanism; peritoneal irritation as inflammation progresses	Classic sequence: periumbilical pain → nausea/vomiting → migration to right lower quadrant; may present atypically in younger children

Developmental Considerations in Children

Several developmental factors affect vomiting in children:

Immature lower esophageal sphincter: Contributes to the high prevalence of physiological reflux in infants (peaks at 4 months, resolves by 12-18 months)
Horizontal stomach position: In infants, the more horizontal gastric axis facilitates regurgitation
Immature coordination of swallowing and breathing: Increases aspiration risk, particularly in neonates and preterm infants
Higher metabolic rate and fluid requirements: Leads to faster development of dehydration with vomiting
Limited glycogen stores: Increases risk of hypoglycemia with prolonged vomiting, especially in infants

Key Neurotransmitters and Antiemetic Targets

Neurotransmitter	Receptor	Location	Antiemetic Agent	Pediatric Notes
Serotonin	5-HT3	Chemoreceptor trigger zone, vagal afferents in gut	Ondansetron, granisetron	First-line for acute gastroenteritis; facilitates oral rehydration
Dopamine	D2	Chemoreceptor trigger zone	Metoclopramide, domperidone, prochlorperazine	Risk of extrapyramidal side effects higher in children; use with caution
Histamine	H1	Vestibular system, vomiting center	Dimenhydrinate, diphenhydramine, promethazine	Useful for motion sickness; sedating effects may be limiting
Acetylcholine	Muscarinic	Vestibular system, vomiting center	Scopolamine	Motion sickness prophylaxis; limited pediatric data for young children
Substance P	NK1	Vomiting center, chemoreceptor trigger zone	Aprepitant, fosaprepitant	Used for chemotherapy-induced vomiting; limited general pediatric use

Complications of Vomiting

Acute Complications

Dehydration: Most common; especially rapid in infants
Electrolyte disturbances: Hypokalemia, hypochloremia, metabolic alkalosis
Hypoglycemia: Particularly in infants and young children
Aspiration pneumonia: Risk increased in neurologically impaired children
Mallory-Weiss tear: Mucosal tear at gastroesophageal junction from forceful vomiting
Boerhaave syndrome: Rare esophageal perforation from severe vomiting

Chronic Complications

Failure to thrive: From caloric loss and reduced intake
Nutritional deficiencies: Vitamins, minerals, protein
Dental erosion: From repeated acid exposure
Esophagitis: From repeated acid exposure
Esophageal stricture: Rare, from chronic severe reflux
Psychological impact: Anxiety, food aversion, school avoidance

Metabolic Consequences of Vomiting

Understanding the metabolic consequences helps guide laboratory evaluation and management:

Loss of gastric acid (H+ and Cl-): Leads to hypochloremic metabolic alkalosis
Potassium loss: Both in vomitus and through renal compensation for alkalosis → hypokalemia
Sodium loss: Contributes to volume depletion
Paradoxical aciduria: Despite systemic alkalosis, kidneys excrete acid to retain sodium and potassium
The classic example: Pyloric stenosis produces hypochloremic, hypokalemic metabolic alkalosis with paradoxical aciduria

3. History Taking

A comprehensive approach to eliciting the vomiting history in children

Red Flags — Require Urgent Evaluation

Bilious (green) vomiting — Intestinal obstruction, malrotation with volvulus
Projectile vomiting in infant 3-6 weeks — Pyloric stenosis
Bloody vomiting (hematemesis) — Upper gastrointestinal bleeding, Mallory-Weiss tear
Severe or worsening abdominal pain — Surgical abdomen, obstruction
Abdominal distension — Bowel obstruction, perforation
Signs of dehydration or shock — Urgent fluid resuscitation needed

Altered consciousness or lethargy — Raised intracranial pressure, metabolic disorder, sepsis
Early morning vomiting with headache — Raised intracranial pressure, brain tumor
Bulging fontanelle — Raised intracranial pressure, meningitis
Neonate with vomiting — Lower threshold for serious pathology
Failure to thrive or weight loss — Chronic serious underlying cause
Recent head injury — Intracranial hemorrhage, concussion

Age-Specific Red Flags

Age Group	Critical Red Flags	Must Consider
Neonate (0-28 days)	Any bilious vomiting, abdominal distension, delayed passage of meconium, lethargy, poor feeding, temperature instability	Malrotation with volvulus, intestinal atresia, Hirschsprung disease, necrotizing enterocolitis, sepsis, inborn errors of metabolism
Infant (1-12 months)	Projectile non-bilious vomiting (3-6 weeks), episodic inconsolable crying with drawing up legs, “currant jelly” stool, bulging fontanelle	Pyloric stenosis, intussusception, meningitis, raised intracranial pressure
Toddler/Preschool	Sudden onset with history of small object access, localized abdominal tenderness, blood in vomit or stool	Foreign body ingestion, intussusception, appendicitis
School-age/Adolescent	Right lower quadrant pain, diabetic patient, sexually active female, signs of eating disorder	Appendicitis, diabetic ketoacidosis, pregnancy, bulimia nervosa

Systematic History: The “VOMITS” Approach

Use the mnemonic “VOMITS” to ensure comprehensive history taking in pediatric vomiting:

V — Volume, Appearance, and Character: How much? What color? Bilious, bloody, or food content? Projectile or effortless?
O — Onset and Duration: When did it start? Acute or chronic? How many episodes? Getting better or worse?
M — Meals and Feeding Relationship: Timing related to feeds? During, immediately after, or delayed? New foods introduced?
I — Illness Features and Associated Symptoms: Fever, diarrhea, abdominal pain, headache, rash? Unwell contacts? Pain characteristics?
T — Timeline and Triggers: Pattern of episodes? Triggers identified? Worse in morning? Related to activity or position?
S — Systemic Review and Red Flags: Hydration status? Weight changes? Neurological symptoms? Urinary symptoms? Growth trajectory?

Targeted Questions by Suspected Cause

Suspected Cause	Key Features	Ask This Question
Acute Gastroenteritis	Acute onset, diarrhea, sick contacts, self-limiting	“Has anyone else at home or daycare been unwell? Is there diarrhea as well? What has the child been able to keep down?”
Pyloric Stenosis	3-6 week old, projectile non-bilious vomiting, hungry after vomiting, firstborn male	“Does the vomiting shoot out forcefully? Does the baby seem hungry right after vomiting and want to feed again?”
Intussusception	6-36 months, episodic severe pain, drawing up legs, pallor, “currant jelly” stool	“Does the child have episodes of severe pain where they draw up their legs and go pale, then seem fine between episodes? Any blood or mucus in the stool?”
Malrotation with Volvulus	Bilious vomiting, abdominal distension, can occur at any age but most common in first month	“Is the vomit green or yellow-green? Has the abdomen become swollen? How quickly did symptoms develop?”
Gastroesophageal Reflux Disease	Frequent regurgitation, irritability during feeds, arching, poor weight gain	“Does the baby seem uncomfortable during or after feeds? Do they arch their back? Is there frequent spitting up affecting weight gain?”
Food Allergy/Intolerance	Onset related to new food introduction, may have blood in stool, eczema, family history of atopy	“When did symptoms start in relation to introducing new foods or formula? Any blood or mucus in stools? Family history of allergies?”
Food Protein-Induced Enterocolitis Syndrome	Profuse vomiting 1-4 hours after specific food, pallor, lethargy, can appear shocked	“Does vomiting occur repeatedly 1-4 hours after eating a specific food? Does the child become pale and lethargic during episodes?”
Raised Intracranial Pressure	Early morning vomiting, headache, visual changes, altered behavior, papilledema	“Is vomiting worse in the morning? Any headaches, especially waking the child at night? Any changes in vision, balance, or personality?”
Cyclic Vomiting Syndrome	Stereotypical episodes, symptom-free intervals, family history of migraine	“Are the episodes predictable and similar each time? Is the child completely well between episodes? Family history of migraines?”
Appendicitis	Periumbilical pain migrating to right lower quadrant, anorexia, low-grade fever	“Did the pain start around the belly button and move to the right lower side? Has the child lost their appetite? Any pain with movement or coughing?”
Urinary Tract Infection	May have no urinary symptoms in young children, fever, irritability	“Any fever? Foul-smelling urine? Pain with urination? Previous urinary infections?”
Diabetic Ketoacidosis	Known diabetic or new presentation, polyuria, polydipsia, weight loss, fruity breath	“Does the child have diabetes? Increased thirst or urination? Recent weight loss? Any sweet or fruity smell to the breath?”
Ingestion/Poisoning	Toddler age, access to medications or toxins, acute onset	“Could the child have gotten into any medications, cleaning products, or other substances? What do you have in the home?”
Pregnancy (Adolescent)	Sexually active, morning nausea, breast tenderness, missed period	“Is there any chance of pregnancy? When was the last menstrual period?” (Ask privately without parent if appropriate)

Essential History Components for Pediatric Vomiting

Birth and Neonatal History

Critical in Infants — Ask About:

Gestational age and birth weight: Prematurity increases risk of feeding difficulties, reflux, necrotizing enterocolitis
Prenatal history: Polyhydramnios suggests esophageal atresia or high intestinal obstruction
Birth complications: Perinatal asphyxia increases risk of feeding difficulties and gastrointestinal dysmotility
NICU admission: Previous intubation increases risk of subglottic stenosis; umbilical lines increase NEC risk
First meconium passage: Delayed passage (>48 hours) suggests Hirschsprung disease or cystic fibrosis
Newborn screening results: May identify metabolic disorders presenting with vomiting

Feeding History

For Infants

Breast or formula fed? Type of formula, any recent changes
Feeding technique: Position, burping, pacing
Volume and frequency: Overfeeding is common cause of regurgitation
Introduction of solids: Timing and types; relation to symptom onset
Feeding behavior: Refuses feeds? Arches? Cries during feeds?

For Older Children

Appetite: Normal, increased, or decreased?
Diet quality: What do they eat and drink?
Relationship to specific foods: Triggers identified?
Eating patterns: Regular meals? Binge eating? Restrictive eating?
Adolescents: Screen for eating disorders (secret eating, purging, excessive exercise)

Developmental History

Assess whether developmental milestones are being met, as neurological conditions causing vomiting may also affect development. Developmental regression is a red flag for neurometabolic disorders. Children with neurodevelopmental disorders have increased risk of gastroesophageal reflux, dysphagia, and aspiration.

Immunization Status

Rotavirus vaccination has significantly reduced severe gastroenteritis hospitalizations. Check pertussis vaccination status if post-tussive vomiting is present. Incomplete vaccination increases risk of vaccine-preventable causes of vomiting.

Medication and Exposure History

Medications That May Cause Vomiting

Antibiotics: Especially erythromycin, amoxicillin-clavulanate — direct gastric irritation and altered gut motility
NSAIDs: Ibuprofen, naproxen — gastric irritation
Iron supplements: Common cause of nausea and vomiting
Chemotherapy: Highly emetogenic, involves multiple pathways
Opioids: Stimulate chemoreceptor trigger zone
Theophylline: Narrow therapeutic window
Digoxin: Toxicity presents with vomiting
Anticonvulsants: Valproate, carbamazepine
Selective serotonin reuptake inhibitors: Especially when starting or dose changes

Ingestion and Exposure History

Accidental ingestion: Medications, household chemicals, plants (especially in toddlers)
Lead exposure: Old housing, imported toys or cosmetics
Carbon monoxide: Faulty heating, enclosed spaces
Recreational substances: In adolescents — alcohol, cannabis, other drugs
Food poisoning sources: Undercooked meat, unpasteurized dairy, buffet foods

Environmental and Social History

Daycare/school attendance: Exposure to infections
Recent travel: Traveler’s diarrhea, tropical infections
Sick contacts: Family, school, daycare
Pets and animals: Reptiles (Salmonella), farm animals
Water source: Well water, swimming in lakes

Family History

Family History	Conditions to Consider
Migraine	Cyclic vomiting syndrome, abdominal migraine
Pyloric stenosis	Recurrence risk 4-7% in siblings, 20% if affected mother
Inflammatory bowel disease	Crohn disease, ulcerative colitis
Atopy (eczema, asthma, allergies)	Food allergy, eosinophilic esophagitis
Metabolic disorders	Inborn errors of metabolism
Consanguinity	Increased risk of autosomal recessive metabolic disorders
Sudden infant death	May indicate underlying metabolic disorder

Assessing Hydration Status by History

History Question	Normal/Mild Dehydration	Moderate Dehydration	Severe Dehydration
Urine output	Normal or slightly reduced	Reduced (fewer wet diapers)	Minimal or absent for 6+ hours
Oral intake	Taking fluids reasonably well	Reduced intake, some fluids tolerated	Unable to tolerate oral fluids
Activity level	Normal or slightly reduced	Less active, tired	Lethargic, difficult to rouse
Tears when crying	Present	Reduced	Absent

4. Physical Examination

A systematic head-to-toe approach for the vomiting child

Systematic Framework: Use the “Head to Extremities” approach for complete examination of children presenting with vomiting. Always begin with assessment of overall appearance, work of breathing, and circulation (the Pediatric Assessment Triangle) to identify the child who requires immediate intervention.

Pediatric Assessment Triangle — First Impression

Appearance

TICLS:

Tone — moving or floppy?
Interactiveness — alert, responds to parents?
Consolability — can be comforted?
Look/Gaze — makes eye contact?
Speech/Cry — strong or weak?

Work of Breathing

Respiratory rate
Retractions (intercostal, subcostal)
Nasal flaring
Abnormal sounds (stridor, wheeze, grunting)
Head bobbing (infants)

Circulation

Skin color (pale, mottled, cyanotic)
Capillary refill time
Peripheral vs central color difference

Abnormal = Urgent Assessment

Growth Parameters

Essential in Every Child with Vomiting

Plot and review growth trajectory — essential for identifying failure to thrive from chronic vomiting:

Weight: Most sensitive indicator of nutritional status and acute dehydration
Length/Height: Affected in chronic malnutrition
Head circumference: In children under 2 years; increased in hydrocephalus, decreased in microcephaly
Weight-for-length/BMI: Assess proportionality
Compare to previous measurements: Crossing percentile lines is more concerning than single measurement

Vital Signs — Age-Appropriate Normal Values

Age	Heart Rate (bpm)	Respiratory Rate (/min)	Systolic BP (mmHg)	Temperature
Neonate (0-28 days)	100-160	30-60	60-90	36.5-37.5°C
Infant (1-12 months)	100-150	25-40	80-100	36.5-37.5°C
Toddler (1-3 years)	90-140	20-30	90-105	36.5-37.5°C
Preschool (3-5 years)	80-120	20-25	95-110	36.5-37.5°C
School-age (6-12 years)	70-110	18-25	100-120	36.5-37.5°C
Adolescent (>12 years)	60-100	12-20	110-130	36.5-37.5°C

Vital Sign Finding	What to Look For	Clinical Significance
Tachycardia	Heart rate above normal for age	Dehydration, fever, pain, anxiety, shock — early compensatory sign
Hypotension	Systolic BP below 5th percentile for age	Late sign of shock in children — indicates decompensation; requires immediate intervention
Fever	Temperature ≥38°C	Infectious cause likely; consider gastroenteritis, UTI, otitis media, meningitis, appendicitis
Hypothermia	Temperature <36°C	Concerning in neonates — may indicate sepsis; also seen in severe dehydration
Tachypnea	Respiratory rate above normal for age	May indicate metabolic acidosis (Kussmaul breathing in diabetic ketoacidosis), pneumonia, compensation for dehydration
Bradycardia	Heart rate below normal for age	Late ominous sign in sick child — may indicate raised intracranial pressure (Cushing reflex) or impending arrest

Assessment of Hydration Status

Sign	Minimal/No Dehydration (<3%)	Mild-Moderate Dehydration (3-9%)	Severe Dehydration (>9%)
Mental status	Alert, active	Restless, irritable, tired	Lethargic, obtunded
Thirst	Normal, may refuse fluids	Thirsty, eager to drink	Unable to drink or too lethargic
Heart rate	Normal	Normal to increased	Tachycardia (bradycardia if near-arrest)
Pulse quality	Normal	Normal to weak	Weak, thready, or impalpable
Breathing	Normal	Normal to fast	Deep (acidotic breathing)
Eyes	Normal	Slightly sunken	Deeply sunken
Tears	Present	Reduced	Absent
Mouth and tongue	Moist	Dry	Parched, cracked
Skin turgor (pinch test)	Instant recoil	Recoil <2 seconds	Recoil >2 seconds (skin tenting)
Capillary refill	<2 seconds	2-3 seconds	>3 seconds
Fontanelle (infants)	Flat	Slightly sunken	Markedly sunken
Extremities	Warm, normal color	Cool peripheries	Cold, mottled, cyanotic
Urine output	Normal to decreased	Decreased	Minimal or absent

Clinical Pearl: Most Useful Dehydration Signs

Studies show the most useful clinical signs for detecting dehydration in children are:

Prolonged capillary refill time (>2 seconds) — best single sign
Abnormal skin turgor — highly specific when present
Absent tears — specific for moderate-severe dehydration
Abnormal respiratory pattern — suggests acidosis
Overall appearance — ill-appearing child is concerning regardless of other signs

No single sign is perfectly sensitive or specific — use combination of findings.

General Inspection

Overall appearance: Well, unwell, toxic, or in extremis? Level of alertness and interaction
Nutritional status: Wasted, well-nourished, or obese? Muscle bulk
Dysmorphic features: May suggest genetic syndrome associated with gastrointestinal anomalies
Color: Pallor (anemia, shock), jaundice (liver disease, hemolysis), cyanosis
Posture: Lying still (peritonitis), drawing up legs (colic, intussusception), opisthotonos (meningitis, tetanus)
Odors: Ketotic/fruity breath (diabetic ketoacidosis, starvation ketosis), feculent (bowel obstruction), ammonia (liver failure)

Head and Neck Examination

Fontanelle (Infants)

Sunken fontanelle: Dehydration
Bulging fontanelle: Raised intracranial pressure (meningitis, hydrocephalus, intracranial mass) — RED FLAG
Full fontanelle when crying: Normal — reassess when calm

Eyes

Sunken eyes: Dehydration
Papilledema (fundoscopy): Raised intracranial pressure — RED FLAG
Sunset sign: Eyes deviated downward — hydrocephalus
Kayser-Fleischer rings: Wilson disease (rare)
Conjunctival pallor: Anemia
Icterus: Jaundice — liver disease, hemolysis

Ears, Nose, and Throat

Otitis media: Red, bulging tympanic membrane — common cause of vomiting in young children
Pharyngitis: Erythema, exudate — streptococcal pharyngitis can present with vomiting and abdominal pain
Dry mucous membranes: Dehydration
Dental erosion: Chronic vomiting (reflux, bulimia)

Neck

Meningismus: Neck stiffness, Kernig sign, Brudzinski sign — meningitis
Lymphadenopathy: Infection, malignancy
Thyromegaly: Thyroid disease

Abdominal Examination

Critical Abdominal Findings Requiring Urgent Action

Visible peristalsis: Intestinal obstruction (especially pyloric stenosis — left to right waves)
Abdominal distension: Obstruction, perforation, ascites
Rigid abdomen/guarding: Peritonitis — surgical emergency
Palpable mass: Intussusception (“sausage-shaped” mass), tumor, pyloric “olive”
Absent bowel sounds: Ileus, peritonitis
High-pitched tinkling bowel sounds: Mechanical obstruction

Inspection

Distension: Generalized (obstruction, ascites) or localized
Visible peristalsis: Gastric waves in pyloric stenosis (left to right in epigastrium)
Scars: Previous surgery
Hernia sites: Inguinal, umbilical — may be incarcerated
Bruising: Trauma (consider non-accidental injury)

Auscultation (Before Palpation)

Hyperactive/high-pitched: Mechanical obstruction, gastroenteritis
Absent: Ileus, peritonitis
Normal: Does not exclude pathology

Palpation

Start away from area of pain — gain child’s trust
Tenderness: Localized versus generalized; superficial versus deep
Guarding: Voluntary (anxiety) versus involuntary (peritonitis)
Rebound tenderness: Peritoneal irritation
Masses: Pyloric “olive” (best felt after vomiting, right upper quadrant), intussusception mass (often right side), fecal loading
Organomegaly: Hepatomegaly, splenomegaly

Specific Signs

Sign	How to Elicit	Positive Finding Suggests
McBurney’s point tenderness	Palpate 1/3 distance from ASIS to umbilicus	Appendicitis
Rovsing sign	Palpate left lower quadrant, pain felt in right lower quadrant	Appendicitis
Psoas sign	Pain on passive right hip extension or active right hip flexion	Retrocecal appendicitis
Obturator sign	Pain on internal rotation of flexed right hip	Pelvic appendicitis
Murphy sign	Arrest of inspiration during right upper quadrant palpation	Cholecystitis (rare in children)
Pyloric “olive”	Firm, mobile, olive-shaped mass in right upper quadrant/epigastrium; best felt after vomiting with stomach empty	Pyloric stenosis
“Sausage-shaped” mass	Elongated mass, often in right upper quadrant or crossing midline	Intussusception
Dance sign	Empty right lower quadrant (cecum drawn up into intussusception)	Intussusception

Hernia Examination

Inguinal region: Check for inguinal hernia — incarcerated hernia causes obstruction and vomiting
Umbilical region: Umbilical hernia — rarely incarcerates
Reducibility: Non-reducible hernia is surgical emergency

Rectal Examination

Not routinely required but consider if:

Suspicion of gastrointestinal bleeding — check for blood
Suspected intussusception — “currant jelly” stool
Suspected Hirschsprung disease — tight anal sphincter, explosive stool release
Assessment of stool quality in constipation

Neurological Examination

Essential when vomiting may have a central cause:

Level of consciousness: Alert, responsive, lethargic, obtunded
Pupil examination: Size, reactivity, symmetry — unilateral dilation suggests herniation
Fundoscopy: Papilledema indicates raised intracranial pressure
Cranial nerves: Sixth nerve palsy (false localizing sign of raised ICP), facial asymmetry, gag reflex
Motor examination: Tone, power, reflexes — asymmetry suggests focal lesion
Coordination: Cerebellar signs (ataxia, dysmetria) — posterior fossa lesions
Gait: If age-appropriate — ataxia, wide-based gait

Signs of Raised Intracranial Pressure

Bulging fontanelle (infants)
Increased head circumference (infants)
“Sunset” eyes
Papilledema
Sixth nerve palsy (inability to abduct eye)
Cushing triad: bradycardia, hypertension, irregular respirations (late sign)
Altered consciousness
Posturing (decerebrate or decorticate)

Other Systems

Genitourinary

Testicular examination in males: Testicular torsion can present with vomiting and abdominal pain
Suprapubic tenderness: Urinary tract infection, urinary retention

Skin

Rashes: Viral exanthems, petechiae/purpura (meningococcemia, Henoch-Schönlein purpura)
Jaundice: Hepatobiliary disease, hemolysis
Bruising: Location and pattern — consider non-accidental injury
Eczema: Associated with food allergy

Expected Findings by Etiology

Condition	General/Vital Signs	Abdominal Findings	Other Key Findings
Acute Gastroenteritis	May have fever; signs of dehydration variable	Mild diffuse tenderness; hyperactive bowel sounds; no peritoneal signs	May have viral exanthem; perianal excoriation from diarrhea
Pyloric Stenosis	Hungry, alert infant; dehydration signs if delayed presentation	Visible gastric peristalsis (left to right); palpable “olive” in RUQ (60-80%); non-distended	Typically 3-6 week old male; may appear well despite significant vomiting
Intussusception	Episodic pallor during pain episodes; may appear well between episodes initially; late: lethargy, shock	“Sausage-shaped” mass (60%); Dance sign (empty RLQ); “currant jelly” stool (late)	Intermittent episodes of severe pain with drawing up of legs
Malrotation with Volvulus	Rapid deterioration; signs of shock	Distension; diffuse tenderness; may have bloody stool	Bilious vomiting; can progress to cardiovascular collapse rapidly
Appendicitis	Low-grade fever; tachycardia; prefers to lie still	RLQ tenderness; guarding; positive psoas/obturator signs; peritoneal signs if perforated	Anorexia prominent; pain with walking or coughing; younger children present atypically
Raised Intracranial Pressure	May have bradycardia, hypertension (Cushing reflex); altered consciousness	Usually non-tender	Bulging fontanelle; papilledema; cranial nerve palsies; ataxia; altered mental status
Diabetic Ketoacidosis	Tachypnea (Kussmaul breathing); dehydration; tachycardia	May have diffuse tenderness (can mimic acute abdomen)	Fruity breath odor; altered consciousness; polyuria history
Urinary Tract Infection	Fever (may be only sign in infants)	May have suprapubic tenderness; usually soft and non-tender	May have no urinary symptoms in young children; irritability
Meningitis	Fever; tachycardia; may be toxic-appearing	Non-specific	Bulging fontanelle (infants); neck stiffness (older children); petechial rash; photophobia; altered consciousness

Important Teaching Point

Normal examination does not exclude serious pathology! Many conditions causing vomiting in children may have unremarkable initial examinations:

Early appendicitis — tenderness may be minimal initially
Intussusception — child may appear completely well between painful episodes
Early pyloric stenosis — before olive becomes palpable
Metabolic disorders — may have normal examination until decompensated
Early raised intracranial pressure — neurological signs may be subtle

Serial examinations and appropriate investigations are essential when clinical suspicion is high.

5. Differential Diagnosis

Systematic approach organized by probability, age, and clinical features

Key Principle: The differential diagnosis for pediatric vomiting varies dramatically by age. Always consider the child’s age first, then organize your differential by probability. Remember that common things are common, but never miss a surgical emergency.

Acute Vomiting (Duration: Less than 7 days)

Probability	Condition	Key Features	Red Flags
COMMON (~70-80%)	Acute Gastroenteritis	Diarrhea, sick contacts, self-limiting, often viral	Severe dehydration, bloody diarrhea, prolonged duration
	Otitis Media	Ear pain, fever, preceding upper respiratory infection, young children	Mastoid tenderness, facial nerve palsy
	Upper Respiratory Tract Infection	Coryza, cough, post-tussive vomiting, low-grade fever	Respiratory distress, prolonged fever
	Urinary Tract Infection	Fever (may be only sign in infants), irritability, poor feeding	Sepsis, pyelonephritis signs, recurrent infections
	Gastroesophageal Reflux	Effortless regurgitation, post-prandial, infant thriving	Poor weight gain, respiratory symptoms, irritability
LESS COMMON (~15-20%)	Appendicitis	Periumbilical pain → right lower quadrant, anorexia, low-grade fever	Perforation signs, peritonitis, toxic appearance
	Pneumonia	Cough, fever, tachypnea, may have abdominal pain	Respiratory distress, hypoxia, sepsis
	Streptococcal Pharyngitis	Sore throat, fever, abdominal pain common in children	Peritonsillar abscess, scarlet fever rash
	Food Poisoning	Rapid onset after contaminated food, often multiple people affected	Bloody vomit/stool, neurological symptoms (botulism)
	Migraine/Abdominal Migraine	Headache, photophobia, family history, episodic pattern	Neurological deficits, altered consciousness
UNCOMMON BUT SERIOUS (~5-10%)	Intussusception	Episodic severe colicky pain, drawing up legs, pallor, 6-36 months	Currant jelly stool, shock, palpable mass
	Pyloric Stenosis	Projectile non-bilious vomiting, 3-6 weeks old, hungry after vomiting	Dehydration, weight loss, palpable olive
	Malrotation with Volvulus	Bilious vomiting, abdominal distension, rapid deterioration	Bilious vomiting, shock, bloody stool — SURGICAL EMERGENCY
	Incarcerated Hernia	Inguinal swelling, pain, irreducible lump	Erythema over hernia, bowel obstruction signs
	Meningitis	Fever, irritability, lethargy, bulging fontanelle (infants)	Petechial rash, neck stiffness, altered consciousness
	Diabetic Ketoacidosis	Polyuria, polydipsia, weight loss, Kussmaul breathing	Altered consciousness, severe dehydration, fruity breath
	Raised Intracranial Pressure	Early morning vomiting, headache, visual changes	Papilledema, cranial nerve palsies, altered consciousness
	Ingestion/Poisoning	Toddler age, access to medications/toxins, acute onset	Altered consciousness, specific toxidromes

Age-Based Differential Diagnosis

Critical: Age is Your Most Important Clue

The causes of vomiting vary dramatically by age. Always frame your differential based on the child’s age first.

Neonatal Period (0-28 days)

Category	Conditions	Key Distinguishing Features
COMMON	Overfeeding, Gastroesophageal reflux, Swallowed maternal blood	Effortless regurgitation, thriving infant, Apt test positive for maternal blood
MUST NOT MISS	Malrotation with volvulus, Intestinal atresia/stenosis, Hirschsprung disease, Necrotizing enterocolitis, Sepsis, Inborn errors of metabolism, Congenital adrenal hyperplasia	Bilious vomiting, abdominal distension, delayed meconium passage, lethargy, temperature instability, ambiguous genitalia

Neonatal Red Flag

Bilious vomiting in a neonate is a surgical emergency until proven otherwise. Malrotation with midgut volvulus must be excluded urgently — bowel necrosis can occur within hours. Obtain immediate surgical consultation and upper gastrointestinal contrast study.

Infant (1-12 months)

Category	Conditions	Key Distinguishing Features
COMMON	Gastroesophageal reflux, Acute gastroenteritis, Overfeeding, Otitis media, Urinary tract infection, Upper respiratory infection	Effortless regurgitation, diarrhea, fever, ear pulling, non-specific symptoms in UTI
LESS COMMON	Pyloric stenosis (3-6 weeks), Food allergy/FPIES, Gastroesophageal reflux disease	Projectile vomiting, vomiting after specific foods, poor weight gain
MUST NOT MISS	Intussusception (peak 6-36 months), Malrotation, Incarcerated hernia, Meningitis, Metabolic disorders, Non-accidental injury	Episodic pain with pallor, bilious vomiting, inguinal mass, bulging fontanelle, lethargy, unexplained bruising

Toddler and Preschool (1-5 years)

Category	Conditions	Key Distinguishing Features
COMMON	Acute gastroenteritis, Upper respiratory infection, Otitis media, Urinary tract infection, Constipation with overflow	Diarrhea, coryza, ear pain, dysuria (if verbal), fecal loading on examination
LESS COMMON	Appendicitis, Pneumonia, Streptococcal pharyngitis, Foreign body ingestion, Cyclic vomiting syndrome	Atypical abdominal pain, tachypnea, sore throat, choking history, stereotypical episodes
MUST NOT MISS	Intussusception, Ingestion/poisoning, Meningitis, Brain tumor, Diabetic ketoacidosis (new onset)	Colicky pain with pallor, access to medications, meningism, early morning vomiting with headache, polyuria/polydipsia

School-Age (6-12 years)

Category	Conditions	Key Distinguishing Features
COMMON	Acute gastroenteritis, Appendicitis, Streptococcal pharyngitis, Migraine, Urinary tract infection	Diarrhea, classic RLQ pain, sore throat, headache with photophobia, dysuria
LESS COMMON	Cyclic vomiting syndrome, Inflammatory bowel disease, Peptic ulcer disease, Pancreatitis, Functional abdominal pain	Stereotypical episodes, bloody diarrhea/weight loss, epigastric pain, severe epigastric pain radiating to back
MUST NOT MISS	Diabetic ketoacidosis, Brain tumor, Testicular torsion (males), Ovarian torsion (females), Meningitis	Kussmaul breathing, early morning vomiting with headache, acute scrotal/pelvic pain, meningism

Adolescent (12-18 years)

Category	Conditions	Key Distinguishing Features
COMMON	Acute gastroenteritis, Appendicitis, Migraine, Pregnancy	Diarrhea, RLQ pain, headache with aura, missed period
LESS COMMON	Eating disorders (bulimia), Substance use, Cyclic vomiting syndrome, Peptic ulcer disease, Inflammatory bowel disease	Weight loss/dental erosion, intoxication, stereotypical episodes, epigastric pain, bloody diarrhea
MUST NOT MISS	Diabetic ketoacidosis, Ectopic pregnancy, Testicular/ovarian torsion, Brain tumor, Pancreatitis	Kussmaul breathing, abdominal pain with positive pregnancy test, acute gonadal pain, early morning vomiting, severe epigastric pain

Chronic Vomiting (Duration: Greater than 7 days)

Step-by-Step Approach to Chronic Vomiting:

Step 1: Assess growth — Is the child thriving or failing to thrive?
Step 2: Characterize the vomiting — Bilious? Bloody? Projectile? Timing?
Step 3: Identify red flags — Any neurological symptoms? Weight loss? Blood?
Step 4: Consider common causes first — Gastroesophageal reflux disease, food allergy, constipation
Step 5: Systematic investigation if no obvious cause identified

Category	Condition	Key Features	Investigation Approach
COMMON	Gastroesophageal Reflux Disease	Regurgitation, irritability, feeding refusal, failure to thrive, respiratory symptoms	Clinical diagnosis initially; pH study/impedance if refractory; endoscopy if alarm features
	Cow’s Milk Protein Allergy	Onset after milk introduction, eczema, bloody stools, family history of atopy	Elimination diet trial; skin prick/specific IgE if IgE-mediated suspected
	Constipation	Infrequent hard stools, fecal loading, overflow soiling	Clinical diagnosis; abdominal radiograph if uncertain
	Post-infectious Gastroparesis	Follows acute gastroenteritis, early satiety, bloating	Gastric emptying study; usually self-resolving
LESS COMMON	Cyclic Vomiting Syndrome	Stereotypical episodes, symptom-free intervals, family history of migraine	Clinical diagnosis (Rome IV criteria); exclude metabolic and anatomical causes
	Eosinophilic Esophagitis	Dysphagia, food impaction, atopic history, failure to thrive	Endoscopy with biopsies showing eosinophilic infiltration
	Peptic Ulcer Disease	Epigastric pain, nocturnal symptoms, Helicobacter pylori risk factors	Endoscopy; H. pylori testing
	Inflammatory Bowel Disease	Bloody diarrhea, weight loss, perianal disease, extraintestinal manifestations	Inflammatory markers, fecal calprotectin, endoscopy with biopsies
UNCOMMON BUT SERIOUS	Brain Tumor/Raised Intracranial Pressure	Early morning vomiting, headache, visual changes, personality change	Urgent neuroimaging (MRI preferred)
	Metabolic Disorders	Episodic with fasting/illness, developmental delay, consanguinity	Metabolic screen during acute episode; specific enzyme/genetic testing
	Intestinal Malrotation (Chronic/Partial)	Intermittent bilious vomiting, failure to thrive, recurrent abdominal pain	Upper gastrointestinal contrast study
	Eating Disorders	Weight loss, body image disturbance, secretive behavior, dental erosion	Detailed psychosocial history; multidisciplinary assessment
	Superior Mesenteric Artery Syndrome	Post-prandial vomiting, weight loss, relief with position change (left lateral/prone)	CT or MR angiography showing reduced aortomesenteric angle

Anatomical Approach to Vomiting

Gastrointestinal — Upper

Gastroesophageal reflux disease

Pyloric stenosis

Gastritis/Peptic ulcer

Eosinophilic esophagitis

Achalasia

Gastric outlet obstruction

Foreign body

Gastrointestinal — Lower

Malrotation with volvulus

Intussusception

Intestinal atresia/stenosis

Hirschsprung disease

Appendicitis

Incarcerated hernia

Inflammatory bowel disease

Central Nervous System

Raised intracranial pressure

Brain tumor

Meningitis/Encephalitis

Hydrocephalus

Migraine

Cyclic vomiting syndrome

Motion sickness

Concussion

Metabolic/Systemic/Other

Diabetic ketoacidosis

Inborn errors of metabolism

Adrenal insufficiency

Urinary tract infection

Sepsis

Drug/toxin ingestion

Food allergy/FPIES

Pregnancy

Drug and Toxin-Induced Vomiting

Drug/Toxin Category	Examples	Mechanism	Specific Features
Antibiotics	Erythromycin, amoxicillin-clavulanate, metronidazole	Direct gastric irritation; erythromycin is motilin agonist	Onset with medication initiation; resolves when stopped
NSAIDs	Ibuprofen, naproxen, aspirin	Gastric mucosal irritation, prostaglandin inhibition	Epigastric pain, may cause gastritis or ulceration
Chemotherapy	Cisplatin, cyclophosphamide, doxorubicin	Chemoreceptor trigger zone stimulation, serotonin release	Highly emetogenic; requires prophylactic antiemetics
Opioids	Codeine, morphine, oxycodone	Chemoreceptor trigger zone stimulation, delayed gastric emptying	Often develops tolerance; constipation contributes
Iron supplements	Ferrous sulfate, ferrous gluconate	Direct gastric irritation	Take with food; may need formulation change
Anticonvulsants	Valproate, carbamazepine, topiramate	Central effects, gastric irritation	May indicate toxicity; check drug levels
Theophylline	Aminophylline, theophylline	Central stimulation, gastric irritation	Narrow therapeutic window; check levels
Digoxin	Digoxin	Chemoreceptor trigger zone stimulation	Vomiting may indicate toxicity; check levels
Household toxins	Iron tablets, paracetamol, cleaning products, plants	Variable — direct GI irritation, systemic toxicity	Toddler age peak; specific toxidromes; contact poison center
Lead	Lead paint, imported toys, traditional remedies	Direct CNS and GI effects	Chronic exposure; developmental delay, abdominal pain
Alcohol/Recreational drugs	Ethanol, cannabis, synthetic cannabinoids	Central effects, gastric irritation, cannabinoid hyperemesis	Adolescents; cyclical pattern with cannabis (hot showers relieve)

Quick Reference: “If You See This, Think This”

Clinical Clue	Think This First	Immediate Action
Bilious (green) vomiting in neonate	Malrotation with volvulus	Urgent surgical consultation; upper GI contrast study
Projectile vomiting, 3-6 week old, hungry after vomiting	Pyloric stenosis	Ultrasound; check electrolytes; surgical referral
Episodic pain with pallor, 6-36 months	Intussusception	Urgent ultrasound; surgical consultation
Early morning vomiting with headache	Raised intracranial pressure/brain tumor	Urgent neuroimaging (CT or MRI)
Vomiting with polyuria, polydipsia, weight loss	Diabetic ketoacidosis	Blood glucose; ketones; urgent management
Vomiting after specific food (1-4 hours), pallor, lethargy	Food protein-induced enterocolitis syndrome	IV fluids if shocked; identify and eliminate trigger food
Infant with fever and no focus	Urinary tract infection (or occult bacteremia)	Urinalysis and culture; consider septic workup if ill
Periumbilical pain → right lower quadrant + vomiting	Appendicitis	Surgical consultation; imaging if diagnosis uncertain
Irreducible inguinal swelling with vomiting	Incarcerated inguinal hernia	Urgent surgical consultation; attempt reduction if viable
Neonate with vomiting, lethargy, hypoglycemia	Inborn error of metabolism or sepsis	Septic workup; metabolic screen; empiric antibiotics
Toddler with sudden vomiting, access to medications	Ingestion/poisoning	Contact poison center; identify substance; supportive care
Adolescent female with vomiting	Pregnancy (always consider)	Pregnancy test
Stereotypical episodes with symptom-free intervals	Cyclic vomiting syndrome	Supportive care during episodes; migraine prophylaxis between
Vomiting with acute scrotal pain (male)	Testicular torsion	Urgent urology consultation; do not delay for imaging

6. Diagnostic Investigations

A stepwise, age-appropriate approach guided by clinical suspicion

Key Principle: Not every child with vomiting needs investigations. Most children with acute vomiting from gastroenteritis can be diagnosed clinically and managed with supportive care. Investigations should be guided by clinical suspicion based on history and examination, and targeted to confirm or exclude specific diagnoses.

When to Investigate

Investigations Usually NOT Needed

Typical acute gastroenteritis with mild dehydration
Single episode of vomiting, child well
Physiological reflux in thriving infant
Clear viral illness with vomiting
Post-tussive vomiting with obvious cause

Investigations Indicated

Red flag features present
Bilious vomiting (urgent)
Moderate-severe dehydration
Chronic or recurrent vomiting
Failure to thrive
Atypical features or diagnostic uncertainty
Suspected surgical cause

Baseline Investigations

When investigations are indicated, consider the following baseline tests:

Investigation	Purpose	What to Look For	Pediatric Considerations
Blood Glucose	Detect hypoglycemia or hyperglycemia	Hypoglycemia (metabolic disorder, prolonged vomiting); Hyperglycemia (diabetic ketoacidosis)	Point-of-care testing allows rapid result; infants at higher risk of hypoglycemia
Electrolytes (Na, K, Cl, HCO3)	Assess dehydration severity and type; guide fluid management	Hyponatremia or hypernatremia; Hypokalemia; Hypochloremic metabolic alkalosis (pyloric stenosis)	Essential in moderate-severe dehydration; guides IV fluid choice
Urea and Creatinine	Assess renal function and dehydration	Elevated urea:creatinine ratio suggests prerenal dehydration	Age-specific reference ranges; creatinine varies with muscle mass
Venous Blood Gas	Assess acid-base status	Metabolic acidosis (dehydration, DKA, sepsis); Metabolic alkalosis (pyloric stenosis, severe vomiting)	Can use capillary sample in children; useful for pH and bicarbonate
Full Blood Count	Infection markers, hemoglobin	Leukocytosis (infection, stress); Anemia (chronic blood loss); Thrombocytosis (inflammation)	Age-specific reference ranges essential; WBC less reliable in young infants
Urinalysis	Screen for UTI; assess hydration (specific gravity); ketones	Nitrites, leukocytes (UTI); High specific gravity (dehydration); Ketones (starvation, DKA); Glucose (DKA)	Clean catch or catheter specimen for culture; bag specimens have high contamination rate
C-Reactive Protein	Inflammatory marker	Elevated in bacterial infection, appendicitis, inflammatory bowel disease	Non-specific; normal does not exclude serious pathology; may be low early in infection

Age-Specific Reference Ranges

Pediatric Laboratory Values Differ from Adults

Always use age-appropriate reference ranges. Key differences include:

White blood cell count: Higher in infants (normal up to 15-17 × 10⁹/L in first year)
Hemoglobin: Physiological nadir at 6-8 weeks; lower normal values than adults until adolescence
Creatinine: Lower in children due to lower muscle mass; increases with age
Alkaline phosphatase: Higher in children due to bone growth

Targeted Investigations by Suspected Cause

Suspected Pyloric Stenosis

First-Line Investigation

Abdominal Ultrasound: Diagnostic test of choice
- Pyloric muscle thickness >3 mm
- Pyloric channel length >15-17 mm
- Sensitivity and specificity >95%

Supporting Investigations

Electrolytes: Classic finding is hypochloremic, hypokalemic metabolic alkalosis
Blood gas: Metabolic alkalosis with pH >7.45
Note: Correct electrolytes before surgery

Suspected Intussusception

First-Line Investigation

Abdominal Ultrasound: Diagnostic test of choice
- “Target sign” or “doughnut sign” on transverse view
- “Pseudokidney sign” on longitudinal view
- Sensitivity >98%, specificity >100%

Therapeutic Investigation

Air or contrast enema: Both diagnostic and therapeutic
- Successful reduction in 80-90%
- Contraindicated if perforation suspected
- Surgical backup required

Suspected Malrotation with Volvulus

Surgical Emergency — Do Not Delay

Upper Gastrointestinal Contrast Study: Gold standard for diagnosis
- Abnormal position of duodenojejunal junction (should be to left of spine at level of pylorus)
- “Corkscrew” or “bird’s beak” appearance in volvulus
Abdominal Ultrasound: May show abnormal superior mesenteric artery/vein relationship (“whirlpool sign”)
Plain Abdominal Radiograph: May be normal early; “double bubble” with distal gas suggests partial obstruction
Key Point: If clinical suspicion is high, proceed to surgery without delay — a normal upper GI study does not completely exclude malrotation

Suspected Appendicitis

Laboratory Investigations

Full blood count: Leukocytosis (>10 × 10⁹/L) with neutrophilia, but may be normal early
C-reactive protein: Often elevated; serial measurements may help
Urinalysis: Mild pyuria/hematuria possible with pelvic appendix; rule out UTI

Imaging

Ultrasound: First-line imaging in children
- Non-compressible appendix >6 mm diameter
- Periappendiceal fluid, appendicolith
- Operator-dependent; non-visualization does not exclude
CT abdomen: Higher sensitivity but radiation exposure; use if US inconclusive and diagnosis uncertain
MRI: Alternative to CT if available; no radiation

Suspected Raised Intracranial Pressure/Brain Tumor

Urgent Imaging

CT Head: Rapid, widely available; good for acute presentations
- Hydrocephalus, mass effect, hemorrhage
- Radiation exposure — minimize in children
MRI Brain: Superior for posterior fossa tumors (common site in children)
- Better soft tissue detail
- No radiation
- May require sedation in young children

Additional Investigations

Fundoscopy: Papilledema indicates raised ICP
Lumbar puncture: CONTRAINDICATED if raised ICP suspected until imaging excludes mass lesion

Suspected Diabetic Ketoacidosis

Investigation	Expected Finding	Diagnostic Criteria
Blood Glucose	Elevated	>11 mmol/L (200 mg/dL)
Venous pH	Acidosis	<7.3 (severe <7.1)
Bicarbonate	Low	<15 mmol/L (severe <5)
Blood/Urine Ketones	Positive	Blood ketones >3 mmol/L; ketonuria
Electrolytes	Variable K+ (total body depleted); Na+ may be low/normal/high	Monitor closely during treatment

Suspected Urinary Tract Infection

Essential Investigations

Urinalysis (dipstick): Nitrites, leukocyte esterase — good for screening
- Nitrites have high specificity but low sensitivity
- Leukocytes more sensitive but less specific
Urine Microscopy and Culture: Confirms diagnosis
- Clean catch, catheter, or suprapubic aspirate (not bag specimens for culture)
- >10⁵ CFU/mL from clean catch; >10⁴ from catheter

Follow-up Imaging

Renal Ultrasound: After first febrile UTI in children
- Structural abnormalities, hydronephrosis
- Urgently if poor response to treatment
DMSA Scan: To assess for renal scarring (4-6 months post-infection)
Voiding Cystourethrogram: Selective use for recurrent UTI or abnormal ultrasound

Suspected Metabolic Disorder

Collect Samples During Acute Episode

Metabolic abnormalities may only be detectable during illness. Collect the following during an acute episode:

Blood: Glucose, ammonia, lactate, blood gas, electrolytes, liver function, uric acid
Blood (freeze for later): Amino acids, acylcarnitine profile
Urine: Ketones, reducing substances, organic acids, amino acids
Consider: Dried blood spot for later analysis if metabolic disorder suspected

Finding	Suggests
Hypoglycemia without ketones	Fatty acid oxidation defect, hyperinsulinism
Hypoglycemia with ketones	Glycogen storage disease, ketotic hypoglycemia
Elevated ammonia	Urea cycle defect, organic acidemia
Metabolic acidosis with high anion gap	Organic acidemia, lactic acidosis
Elevated lactate	Mitochondrial disorder, tissue hypoperfusion

Suspected Gastroesophageal Reflux Disease / Chronic Vomiting

Initial Approach

Clinical diagnosis first: No investigations needed if typical GERD and responding to conservative management
Trial of therapy: Can be diagnostic — response to acid suppression supports diagnosis

Further Investigations if Indicated

Upper GI Endoscopy: If alarm features, treatment failure, suspected eosinophilic esophagitis
24-hour pH/Impedance Study: Gold standard for quantifying reflux; correlate symptoms with reflux episodes
Upper GI Contrast Study: To exclude anatomical abnormalities (not for diagnosing GERD)
Gastric Emptying Study: If gastroparesis suspected

Summary: Investigation by Clinical Scenario

Clinical Scenario	First-Line Investigation	Additional if Needed
Typical acute gastroenteritis, mild dehydration	None — clinical diagnosis	Stool culture if bloody, prolonged, outbreak
Moderate-severe dehydration	Electrolytes, glucose, urea, blood gas	Full septic workup if toxic-appearing
Bilious vomiting (any age)	Upper GI contrast study (urgent)	Surgical consultation — do not delay
Projectile vomiting, 3-6 week old	Abdominal ultrasound; electrolytes, blood gas	Surgical referral
Episodic pain with pallor, 6-36 months	Abdominal ultrasound	Air/contrast enema if positive
Fever without focus in infant	Urinalysis, urine culture; consider FBC, CRP, blood culture	Lumbar puncture if <3 months or toxic
Suspected appendicitis	FBC, CRP, urinalysis; abdominal ultrasound	CT if diagnosis uncertain and high suspicion
Early morning vomiting with headache	CT head (urgent) or MRI brain	Neurosurgical consultation if abnormal
Suspected DKA	Blood glucose, ketones, blood gas, electrolytes	Monitor closely; follow DKA protocol
Chronic vomiting with failure to thrive	Baseline bloods; consider upper GI contrast, endoscopy	Metabolic screen; specialist referral
Suspected ingestion/poisoning	Specific levels if indicated (paracetamol, salicylate); ECG	Contact poison center; specific antidotes
Adolescent female with vomiting	Pregnancy test	As indicated by other features

Empiric Treatment Trials as Diagnostic Tools

Response to Treatment Can Support Diagnosis

In some situations, a therapeutic trial can help confirm the diagnosis:

Suspected Gastroesophageal Reflux Disease: Trial of proton pump inhibitor for 4-8 weeks — improvement supports diagnosis
Suspected Cow’s Milk Protein Allergy: Elimination of cow’s milk protein for 2-4 weeks — resolution of symptoms supports diagnosis; confirm with supervised reintroduction
Suspected Constipation: Trial of disimpaction and maintenance laxatives — resolution of vomiting suggests constipation was the cause
Suspected Cyclic Vomiting Syndrome: Trial of migraine prophylaxis (e.g., amitriptyline, cyproheptadine) — reduction in episode frequency supports diagnosis

Pediatric-Specific Investigation Considerations

Minimize radiation exposure: Use ultrasound first where possible; avoid CT unless necessary
Consider sedation needs: Young children may need sedation for MRI and some procedures
Use age-appropriate specimen collection: Clean catch urine may be difficult in infants; catheter or suprapubic aspirate more reliable
Blood volume considerations: Minimize the number and volume of blood tests in small infants
Involve parents: Parental presence can reduce distress during investigations
Use topical anesthesia: EMLA or similar for blood draws to reduce pain and distress

7. Pattern Recognition and Clinical Decision-Making

Practical algorithms and decision pathways for pediatric vomiting

Step 1: Is This Urgent? — Triage Assessment

Clinical Scenario	Urgency Level	Immediate Action
Bilious (green) vomiting in neonate or infant	EMERGENT	NPO, IV access, NG decompression, urgent surgical consultation, upper GI contrast study — do NOT delay
Signs of shock (mottled, cold, tachycardia, poor perfusion)	EMERGENT	IV/IO access, 20 mL/kg fluid bolus, identify and treat cause, prepare for resuscitation
Altered consciousness or unresponsive	EMERGENT	Airway protection, check glucose, IV access, urgent neuroimaging if raised ICP suspected
Severe dehydration (>9%)	EMERGENT	IV/IO access, 20 mL/kg normal saline bolus, reassess, repeat as needed
Bulging fontanelle with vomiting	EMERGENT	Urgent CT head, neurosurgical consultation, treat raised ICP
Irreducible inguinal hernia with vomiting	EMERGENT	Urgent surgical consultation, attempt reduction if viable, prepare for surgery
Suspected intussusception (episodic pain, pallor, mass)	URGENT	IV access, urgent ultrasound, surgical consultation, prepare for enema reduction
Projectile vomiting in 3-6 week old	URGENT	Ultrasound, check electrolytes, IV fluids, surgical referral for pyloromyotomy
Suspected appendicitis	URGENT	IV access, analgesia, NPO, bloods, imaging (US first), surgical consultation
Suspected diabetic ketoacidosis	URGENT	Check glucose and ketones, IV access, begin DKA protocol, monitor closely
Early morning vomiting with headache	URGENT	Neurological examination, fundoscopy, urgent neuroimaging
Moderate dehydration (3-9%)	URGENT	Attempt oral rehydration with ondansetron; IV fluids if oral fails
Febrile infant <3 months with vomiting	URGENT	Full septic workup including LP, empiric antibiotics, admission
Suspected ingestion/poisoning	URGENT	Contact poison center, identify substance, supportive care, specific antidotes if indicated
Mild dehydration with typical gastroenteritis	ROUTINE	Oral rehydration therapy, ondansetron if needed, safety-net advice, outpatient management
Chronic vomiting, child well and thriving	ROUTINE	Outpatient investigation, consider GERD management, specialist referral if needed
Physiological reflux in thriving infant	ROUTINE	Reassurance, feeding advice, anticipatory guidance — no investigations needed

Step 2: Classify by Age and Duration

Age Categories

Neonate (0-28 days): High suspicion for congenital anomalies, sepsis, metabolic disorders
Infant (1-12 months): Consider pyloric stenosis (3-6 weeks), intussusception (6+ months)
Toddler (1-3 years): Ingestion risk, atypical appendicitis presentation
School-age (3-12 years): Classic appendicitis, cyclic vomiting syndrome
Adolescent (>12 years): Always consider pregnancy; eating disorders; adult-pattern causes

Duration Categories

Acute (<7 days): Infection most common; exclude surgical emergencies
Chronic (>7 days): Systematic evaluation needed; consider anatomical, neurological, metabolic, allergic causes
Recurrent/Cyclic: Stereotypical episodes with well intervals — think cyclic vomiting syndrome, abdominal migraine, metabolic disorders

Step 3: Algorithm by Presentation

Algorithm A: Acute Vomiting — Well-Appearing Child

Clinical Scenario	Most Likely Diagnosis	Action
Vomiting + diarrhea + sick contacts + mild dehydration	Acute viral gastroenteritis	Oral rehydration, ondansetron if needed, safety-net advice, discharge home
Vomiting + fever + ear pain/tugging	Acute otitis media	Examine ears, analgesia, antibiotics if indicated, oral fluids
Vomiting + coryza + cough	Upper respiratory tract infection	Supportive care, oral fluids, safety-net advice
Vomiting + fever + no focus (infant)	Urinary tract infection (consider occult bacteremia)	Urinalysis and culture, consider septic workup in young infants
Single vomiting episode, child well, tolerating fluids	Non-specific/self-limiting	Observation, oral fluids, reassure, safety-net advice

Algorithm B: Acute Vomiting — Red Flags Present

Clinical Scenario	Most Likely Diagnosis	Action
Bilious vomiting at any age	Intestinal obstruction — malrotation with volvulus until proven otherwise	NPO, IV fluids, NG tube, urgent upper GI study, surgical consultation — EMERGENCY
Projectile non-bilious vomiting, 3-6 weeks old, hungry after vomiting	Pyloric stenosis	Ultrasound, electrolytes/gas, IV fluids, correct alkalosis, surgical referral
Episodic severe pain with pallor, drawing up legs, 6-36 months	Intussusception	Ultrasound, surgical consultation, air/contrast enema for reduction
Periumbilical → right lower quadrant pain, anorexia, low-grade fever	Appendicitis	NPO, IV fluids, analgesia, bloods, imaging, surgical consultation
Irreducible inguinal swelling + vomiting	Incarcerated inguinal hernia	Urgent surgical consultation, attempt gentle reduction if viable bowel
Early morning vomiting + headache ± visual changes	Raised intracranial pressure	Urgent CT/MRI, neurosurgical consultation
Vomiting + polyuria + polydipsia + weight loss	Diabetic ketoacidosis	Check glucose and ketones, begin DKA protocol, close monitoring
Vomiting + fever + neck stiffness + bulging fontanelle	Meningitis	Lumbar puncture (if safe), empiric antibiotics, supportive care
Neonate with vomiting + lethargy + poor feeding	Sepsis or metabolic disorder	Full septic workup, metabolic screen, empiric antibiotics, NICU involvement

Algorithm C: Chronic or Recurrent Vomiting

Clinical Scenario	Most Likely Diagnosis	Action
Infant with effortless regurgitation, thriving, happy	Physiological gastroesophageal reflux	Reassurance, feeding advice, no investigation needed
Infant with regurgitation + irritability + poor weight gain + feeding refusal	Gastroesophageal reflux disease	Trial of acid suppression, consider allergy evaluation, endoscopy if alarm features
Vomiting after cow’s milk introduction + eczema + bloody stools	Cow’s milk protein allergy	Elimination diet trial, specialist referral if complex
Stereotypical intense vomiting episodes with well intervals + migraine family history	Cyclic vomiting syndrome	Supportive care during episodes, migraine prophylaxis between episodes
Chronic vomiting + failure to thrive + developmental delay	Metabolic disorder or neurological cause	Metabolic workup, neuroimaging, specialist referral
Adolescent with vomiting + weight loss + body image concerns	Eating disorder (bulimia nervosa)	Sensitive history, multidisciplinary assessment, psychiatric referral

“What Do I Do If…” Decision Reference

Clinical Situation	Immediate Action	Next Step
Child cannot tolerate oral fluids despite ondansetron	IV access, begin IV rehydration	Reassess for underlying cause; consider admission if not improving
Unsure if vomiting is bilious	If any doubt — treat as bilious and investigate urgently	Upper GI contrast study, surgical consultation
Pyloric ultrasound equivocal	Repeat ultrasound after 24-48 hours, or upper GI contrast study	Surgical consultation for clinical correlation
Air enema fails to reduce intussusception	Second attempt may be tried in stable child	Surgical reduction if repeated attempts fail or child unstable
Child with vomiting wants to eat	Allow small, frequent feeds of tolerated foods once rehydrated	Do not restrict diet unnecessarily — early feeding aids recovery
Parents request antiemetic for mild gastroenteritis	Ondansetron safe and effective if needed to facilitate ORT	Single dose often sufficient; provide ORT instructions
Vomiting child in DKA — how aggressive with fluids?	Careful rehydration over 24-48 hours — cerebral edema risk	Follow established DKA protocol; avoid rapid fluid shifts
Adolescent denies possibility of pregnancy	Still perform pregnancy test — history may be unreliable	Document result; ensure confidentiality if positive
Parents want to give oral medications but child keeps vomiting	Consider ondansetron ODT (orally disintegrating tablet) or rectal/IV route	Once vomiting controlled, can try oral medications
Child vomiting after head injury	Assess using pediatric head injury guidelines (PECARN)	CT head if criteria met; observation if low risk
Infant vomiting — unsure if normal reflux or pathological	Plot weight, assess feeding, look for red flags	If thriving with no red flags — reassure; if failure to thrive or red flags — investigate
Child improving but parents anxious about discharge	Clear discharge criteria met? Provide thorough safety-net advice	Written instructions, when to return, 24-hour follow-up option

Oral Rehydration Strategy

Oral Rehydration Therapy (ORT) — First Line for Mild-Moderate Dehydration

Rehydration Phase

Mild dehydration (3-5%): 50 mL/kg over 4 hours
Moderate dehydration (6-9%): 100 mL/kg over 4 hours
Give small, frequent volumes (5-10 mL every 2-5 minutes)
Syringe or teaspoon for young children
Ondansetron can facilitate ORT by reducing vomiting

Maintenance Phase

Replace ongoing losses plus maintenance requirements
Continue breastfeeding throughout
Resume normal diet once rehydrated
Avoid high-sugar drinks (juice, soft drinks)
Use oral rehydration solution (ORS) — not sports drinks

When to Involve Specialists

Specialist	When to Refer
Pediatric Surgery	Bilious vomiting, suspected pyloric stenosis, intussusception, appendicitis, incarcerated hernia, any suspected surgical abdomen
Pediatric Gastroenterology	Chronic vomiting unresponsive to initial management, suspected inflammatory bowel disease, eosinophilic esophagitis, complex food allergies, failure to thrive
Pediatric Neurology/Neurosurgery	Suspected raised intracranial pressure, brain tumor, cyclic vomiting syndrome resistant to treatment
Pediatric Endocrinology	New onset diabetes/DKA, suspected adrenal insufficiency
Metabolic Medicine	Suspected inborn error of metabolism, recurrent vomiting with hypoglycemia or acidosis
Pediatric Allergy	Suspected food protein-induced enterocolitis syndrome, multiple food allergies, eosinophilic gastrointestinal disorders
Adolescent Medicine/Psychiatry	Suspected eating disorder, psychogenic vomiting

Troubleshooting Refractory Vomiting

When Vomiting Persists Despite Treatment — Ask These Questions

Is the diagnosis correct? Re-evaluate history and examination; consider alternative diagnoses
Is there a surgical cause being missed? Lower threshold for imaging and surgical consultation
Are there multiple overlapping causes? A child can have gastroenteritis AND appendicitis
Is there an underlying chronic condition? Metabolic disorder, neurological cause, eosinophilic disease
Is the treatment adequate? Correct antiemetic, correct dose, correct duration?
Is compliance an issue? Medication being vomited up? Route of administration appropriate?
Is this an unusual presentation of a common condition? Atypical appendicitis, diabetic ketoacidosis without known diabetes
Have red flags been reassessed? New red flags may have developed
Is there psychogenic contribution? Particularly in adolescents with chronic vomiting

Discharge Criteria and Safety-Net Advice

Safe to Discharge When:

Tolerating oral fluids
Adequate urine output
No red flag features
Parents confident with home management
Access to medical care if needed
Improving trend, not worsening

Safety-Net: Return If:

Unable to keep fluids down
Vomiting becomes bilious (green)
Blood in vomit
Increasing abdominal pain
Becoming less responsive or more lethargic
Not passing urine
Symptoms worsening or not improving as expected
Parents concerned for any reason

8. Clinical Pearls and Pitfalls

Practical wisdom — learn from successes and avoid common mistakes

Must-Know Clinical Pearls

Bilious vomiting is a surgical emergency until proven otherwise: In neonates, bilious (green) vomiting means malrotation with midgut volvulus until proven otherwise. Bowel can become necrotic within hours — never delay investigation.

Age is your most important diagnostic clue: The differential diagnosis changes dramatically by age. Pyloric stenosis at 3-6 weeks, intussusception at 6-36 months, appendicitis in school-age children — always think “What diagnoses are most likely at this age?”

The child who looks well between episodes of severe pain needs urgent evaluation: This pattern is classic for intussusception. The child may appear completely normal between episodes, which can falsely reassure clinicians.

Ondansetron facilitates oral rehydration and reduces IV fluid use: A single dose of ondansetron significantly reduces vomiting and allows more children to be successfully rehydrated orally, avoiding the need for IV access.

The pyloric “olive” is best felt after vomiting: Palpate for the pyloric mass in the right upper quadrant or epigastrium after the infant has vomited and the stomach is empty. Feed the infant and observe for visible peristalsis (gastric waves from left to right).

Vomiting + fever without source in infants = UTI until proven otherwise: Young infants with UTI often have no urinary symptoms — vomiting and fever may be the only signs. Always check urine in febrile infants.

Physiological reflux in thriving infants resolves spontaneously: Up to 50% of infants have regurgitation, peaking at 4 months and resolving by 12-18 months. If the infant is thriving and happy, reassure parents — no investigations or medications needed.

Capillary refill time is the single best clinical sign for dehydration: Prolonged capillary refill >2 seconds has the best combination of sensitivity and specificity for detecting dehydration. Combine with other signs for best assessment.

Cyclic vomiting syndrome is a diagnosis of exclusion but follows a recognizable pattern: Stereotypical episodes with symptom-free intervals, often with migraine family history. Always exclude metabolic and anatomical causes first, especially if episodes are triggered by fasting or illness.

Early morning vomiting without nausea should raise suspicion for raised intracranial pressure: Posterior fossa tumors are common in children and can present with vomiting as the predominant symptom. Always examine fundi and assess neurological status.

Critical Pitfalls to Avoid

Dismissing bilious vomiting as gastroenteritis: Green vomit is bile. Bile means obstruction distal to the ampulla of Vater until proven otherwise. Never attribute bilious vomiting to viral illness — this can result in missed malrotation with catastrophic bowel necrosis.

Assuming a normal examination excludes serious pathology: Children with intussusception can appear completely well between episodes. Early appendicitis may have minimal tenderness. Early pyloric stenosis may not have a palpable olive. Serial examinations are essential.

Forgetting to check a pregnancy test in adolescent females: Always perform a pregnancy test in any adolescent female with vomiting, regardless of stated sexual history. History may be unreliable, and missing pregnancy (or ectopic pregnancy) can have serious consequences.

Missing diabetic ketoacidosis presenting as gastroenteritis: New-onset diabetes in children often presents with vomiting and abdominal pain that mimics gastroenteritis. Check blood glucose in any child with unexplained vomiting, especially if dehydration seems disproportionate to history.

Attributing neurological symptoms to dehydration alone: While severe dehydration can cause lethargy, altered consciousness that seems out of proportion to the degree of dehydration should prompt evaluation for meningitis, metabolic disorder, or raised intracranial pressure.

Delaying surgical consultation for “more investigation”: When a surgical emergency is suspected (bilious vomiting, suspected volvulus, incarcerated hernia), involve surgery immediately. Investigation and surgical consultation should happen in parallel, not sequentially.

Correcting pyloric stenosis electrolytes too rapidly: Children with pyloric stenosis have hypochloremic, hypokalemic metabolic alkalosis. Correct electrolytes gradually over 24-48 hours before surgery — rapid correction can cause complications.

Forgetting to examine the hernial orifices: An incarcerated inguinal hernia can cause bowel obstruction and vomiting. Always examine inguinal regions, especially in infants with unexplained vomiting or irritability.

Using adult chronic cough definitions for chronic vomiting: Pediatric definitions and thresholds often differ from adults. Understand age-specific presentations and disease patterns — children are not small adults.

Missing ingestion in toddlers: Toddlers are mobile, curious, and put everything in their mouths. Always consider accidental ingestion of medications or household products in a toddler with unexplained vomiting. Ask specifically about medications in the home.

Key Takeaways

Bilious vomiting = surgical emergency — Malrotation with midgut volvulus must be excluded urgently in any child with green vomiting. Do not attribute to gastroenteritis.
Age guides your differential — The most likely causes of vomiting change dramatically across pediatric age groups. Always consider age-specific diagnoses first.
Most acute vomiting is viral gastroenteritis — But never become complacent. Always look for red flags and consider surgical emergencies.
Dehydration assessment is clinical — Combine multiple signs (capillary refill, skin turgor, mucous membranes, mental status) for best accuracy. No single sign is perfect.
Oral rehydration is first-line treatment — With ondansetron if needed. Reserve IV fluids for those who fail oral rehydration or have severe dehydration.
The well-appearing child can still have serious pathology — Intussusception classically presents with pain-free intervals. Pyloric stenosis infants often appear hungry and well. Serial assessment is key.
Think of the abdomen for extra-abdominal causes — UTI in infants, diabetic ketoacidosis, raised intracranial pressure, and meningitis can all present with prominent vomiting.
Always consider pregnancy in adolescents — Regardless of stated history, perform a pregnancy test. Confidentiality is important.
Physiological reflux in thriving infants needs reassurance, not investigation — Educate parents about normal infant regurgitation and its natural resolution by 12-18 months.
Safety-net advice is essential — Clearly explain when to return, provide written instructions, and ensure parents feel confident to seek help if needed.

Quick Reference Algorithm

Systematic Approach to the Vomiting Child:

Assess urgency: Airway, Breathing, Circulation — Is the child stable? Signs of shock or severe dehydration?
Identify red flags: Bilious vomiting, projectile vomiting in 3-6 week old, altered consciousness, bulging fontanelle, bloody vomit, severe abdominal pain
Consider age: What diagnoses are most likely at this child’s age?
Characterize the vomiting: Duration (acute vs chronic), character (bilious vs non-bilious, bloody), pattern (timing, projectile, cyclic)
Assess hydration status: Use clinical signs to classify as minimal, mild-moderate, or severe dehydration
Perform targeted examination: Abdomen (distension, masses, tenderness, hernias), neurological (if CNS cause suspected), growth parameters
Investigate guided by clinical suspicion: Not every child needs tests — investigate to confirm or exclude specific diagnoses
Treat the underlying cause: Surgical referral if indicated; supportive care with rehydration for most medical causes
Reassess and adjust: If not improving as expected, reconsider the diagnosis and investigate further
Provide clear safety-net advice: When to return, warning signs, follow-up plans

Summary Decision Aid

If You See…	Think…	Do…
Green (bilious) vomiting	Malrotation with volvulus	Urgent upper GI study + surgical consultation — EMERGENCY
Projectile vomiting, 3-6 week old	Pyloric stenosis	Ultrasound + electrolytes + surgical referral
Episodic pain with pallor, 6-36 months	Intussusception	Urgent ultrasound + surgical consultation
Early morning vomiting + headache	Raised intracranial pressure	Urgent neuroimaging
Vomiting + polyuria + polydipsia	Diabetic ketoacidosis	Check glucose + ketones + begin DKA protocol
Vomiting + diarrhea + mild dehydration	Acute gastroenteritis	Oral rehydration ± ondansetron
Thriving infant with effortless regurgitation	Physiological reflux	Reassurance + feeding advice — no tests needed
Adolescent female with vomiting	Pregnancy (always consider)	Pregnancy test