STONE Score Calculator
Estimate the likelihood of ureteral stone in patients presenting with acute flank pain. The STONE score combines five bedside predictors to stratify patients into low, moderate, and high probability categories — helping guide imaging decisions in the emergency department.
Calculate STONE Score
Enter the five bedside predictors below to estimate the probability of ureteral stone in an adult patient presenting with flank or back pain suggestive of renal colic. All criteria are assessed at the time of emergency department presentation.
The STONE score is a screening tool designed to estimate the pre-test probability of ureteral stone. It does not replace CT imaging for definitive diagnosis and should be interpreted alongside the full clinical picture. The race-based criterion (“Origin”) has been subject to debate — a revised version without race has been proposed.
Understanding the STONE Score
The STONE score was derived and validated by Moore et al. in 2014 as a clinical prediction rule for uncomplicated ureteral stone. It was developed to help emergency clinicians estimate the likelihood that a patient presenting with acute flank pain has a ureteral calculus — and, critically, to identify patients with a high probability of stone who have a low likelihood of important alternative diagnoses.
The acronym stands for five bedside predictors that were identified through multivariate logistic regression from a derivation cohort of 1,040 patients: Sex, Timing (duration of pain), Origin (race), Nausea/vomiting, and Erythrocytes (haematuria on dipstick). Each factor is assigned weighted points based on its association with ureteral stone on CT imaging.
Scoring Formula
STONE Score =
Sex (0 or 2) +
Timing (0, 1, or 3) +
Origin (0 or 3) +
Nausea (0, 1, or 2) +
Erythrocytes (0 or 3)
Total range: 0 – 13 points
Worked Example
A 42-year-old male with 4 hours of left flank pain, non-black race, vomiting, and haematuria on dipstick:
Sex (2) + Timing (3) + Origin (3) + Nausea (2) + Erythrocytes (3) = 13 points → High probability
Key distinction: The STONE score estimates the probability of ureteral stone (not all renal stones). It was designed for patients undergoing CT for suspected nephrolithiasis and is most useful for guiding whether imaging can be deferred or dose-reduced, not for making a definitive diagnosis.
Interpretation & Risk Categories
The STONE score classifies patients into three probability groups based on data from both the original derivation/validation cohorts and subsequent external validation studies.
| Score Range | Risk Category | Stone Probability (Derivation) | Stone Probability (Validation) | Alternative Diagnoses |
|---|---|---|---|---|
| 0 – 5 | Low | ~8% | ~9% | Higher likelihood of important alternate findings |
| 6 – 9 | Moderate | ~52% | ~51% | CT typically recommended |
| 10 – 13 | High | ~90% | ~89% | Very low (<2%) rate of important alternate findings |
In the high-score group, acutely important alternative findings (appendicitis, AAA, ovarian torsion, etc.) were present in only 0.3% of the derivation cohort and 1.6% of the validation cohort. This makes the high-score group a potential candidate for reduced-dose CT or point-of-care ultrasound rather than standard-dose CT.
Differential Diagnosis in Acute Flank Pain
Not every patient with flank pain has nephrolithiasis. The STONE score was designed, in part, to identify patients who may harbour important alternative diagnoses. The following differentials should be considered, particularly in patients with low STONE scores.
Pyelonephritis presents with flank pain, fever, and pyuria, and may mimic renal colic. Unlike nephrolithiasis, patients typically have systemic signs of infection including rigors and costovertebral angle tenderness with positive urinalysis for leukocytes and nitrites. Urinalysis showing both haematuria and pyuria should raise suspicion for infected obstructing stone — a urological emergency.
Ureteropelvic junction (UPJ) obstruction may cause episodic flank pain mimicking renal colic, particularly with diuresis. Imaging reveals hydronephrosis without a visible stone. Renal papillary necrosis, commonly associated with analgesic nephropathy, sickle cell disease, or diabetes, can present identically to ureteral stone with passage of sloughed papillae.
Abdominal aortic aneurysm (AAA) is the most dangerous mimic of renal colic, particularly in older males with cardiovascular risk factors. The classic triad of abdominal/flank pain, pulsatile abdominal mass, and hypotension is present in fewer than 50% of cases. Haematuria may occur from renal vein involvement. All patients over 60 with first-episode flank pain should have AAA considered, regardless of STONE score.
Renal artery dissection or thromboembolism may present with acute flank pain and haematuria. Risk factors include atrial fibrillation, recent cardiac catheterisation, and connective tissue disorders. CT angiography is required for diagnosis. Renal infarction can also mimic renal colic and should be considered in patients with embolic risk factors and an LDH disproportionately elevated relative to other markers.
Appendicitis may present with right flank or right lower quadrant pain that can be confused with right ureteral colic. The presence of pyuria (which occurs in up to 20% of appendicitis cases due to proximity of the inflamed appendix to the ureter) may further complicate the picture. Serial examination, inflammatory markers, and cross-sectional imaging are key differentiators.
Cholecystitis and biliary colic can radiate to the right flank and may be mistaken for right renal colic. Diverticulitis, particularly sigmoid, may present as left flank pain. Mesenteric ischaemia should be considered in older patients with atrial fibrillation or vascular disease presenting with abdominal or flank pain disproportionate to examination findings.
Ovarian torsion is a surgical emergency that may present as sudden-onset unilateral flank or lower abdominal pain with nausea and vomiting — closely mimicking renal colic. Point-of-care ultrasound demonstrating an enlarged ovary with absent or diminished Doppler flow supports the diagnosis. Ectopic pregnancy must be excluded in all women of childbearing age presenting with flank or lower abdominal pain; a bedside urine pregnancy test is mandatory.
Ruptured ovarian cyst and mittelschmerz may also present with acute-onset unilateral pain. The pain is typically more pelvic in location but can radiate to the flank. The timing relative to the menstrual cycle and presence or absence of haematuria can help differentiate these from renal colic.
Musculoskeletal pain from paraspinal muscle strain or thoracolumbar radiculopathy may present as flank pain that is worsened by movement and palpation. The pain tends to be more positional and reproducible on examination, unlike the colicky nature of renal colic. Herpes zoster (shingles) in the T10–L1 dermatome can cause unilateral flank pain that precedes the characteristic vesicular rash by several days.
Lower lobe pneumonia or pulmonary embolism may occasionally present with pleuritic pain referred to the flank. A chest radiograph or CT pulmonary angiogram may be appropriate in patients with respiratory symptoms, hypoxia, or risk factors for venous thromboembolism.
A low STONE score does not exclude ureteral stone — approximately 8–14% of patients in the low-risk group still have stones on CT. More importantly, low-score patients have a higher rate of acutely important alternative diagnoses. Maintain a broad differential, particularly in older patients, females, and those with atypical presentations.
Special Populations & the Race Criterion
Clinical note: In populations where nearly all patients are non-Black (e.g., many Middle Eastern, Asian, or European settings), the “Origin” criterion effectively adds 3 points to every patient. Clinicians in these settings should be aware that the score’s discriminatory power may be reduced, and the “moderate” and “high” thresholds should be interpreted with this in mind.
Common Pitfalls & Limitations
Even in the high-score group, approximately 10% of patients do not have a ureteral stone. A high STONE score increases the probability of stone but does not provide definitive diagnosis. External validation studies have shown that the positive predictive value of a high score ranges from 73% to 90% depending on the study population and disease prevalence. Clinicians should not forgo imaging in patients who require it for management decisions, such as stone size measurement to guide intervention versus expectant management.
The STONE score was designed to estimate probability, not to recommend a specific course of action. Unlike decision instruments such as the PERC rule for pulmonary embolism, the STONE score has not been prospectively validated as a tool to safely defer CT imaging. Patients in the high-score group may still require CT to determine stone size and location — information critical for deciding between conservative management and urological intervention. The score is best used as one input in shared decision-making, not as a standalone imaging gatekeeper.
Patients with low STONE scores have a higher prevalence of acutely important alternative findings (AIAFs) such as appendicitis, ovarian pathology, and vascular emergencies. In the original validation, 3.8% of all patients had an AIAF — but these were concentrated in the low and moderate score groups. Clinicians must maintain a broad differential in low-score patients rather than simply concluding “no stone” and discharging. These patients may require CT regardless of a low stone probability because the clinical question shifts to “what else could this be?”
Haematuria is the most heavily weighted criterion in the STONE score (3 points), yet it is neither sensitive nor specific for nephrolithiasis in isolation. Up to 10–30% of patients with confirmed ureteral stones have no haematuria on dipstick testing, and haematuria may be present in many alternative conditions including UTI, malignancy, anticoagulant use, renal vein thrombosis, and vigorous exercise. The absence of haematuria should not be used alone to exclude stone, nor should its presence be treated as confirmatory.
The STONE score was derived in adults (≥18 years) undergoing non-contrast CT for suspected uncomplicated nephrolithiasis. Exclusion criteria in the original study included known active malignancy, renal disease (creatinine >1.5 mg/dL), evidence of infection (fever or leukocytes on dipstick), recent urological procedures, and history of trauma. Applying the score to patients who would have been excluded from the derivation cohort — such as those with suspected pyelonephritis, known cancer, or chronic kidney disease — may produce unreliable results.
Quick Reference Summary
(5 criteria)
Low score (0–5)
Moderate score (6–9)
High score (10–13)
| Criterion | Options | Points |
|---|---|---|
| S — Sex | Male / Female | 2 / 0 |
| T — Timing | <6 h / 6–24 h / >24 h | 3 / 1 / 0 |
| O — Origin | Non-Black / Black | 3 / 0 |
| N — Nausea | Vomiting / Nausea / None | 2 / 1 / 0 |
| E — Erythrocytes | Present / Absent | 3 / 0 |
A high STONE score (10–13) suggests a very high probability of ureteral stone and a very low probability of important alternative diagnoses — but it does not eliminate the need for imaging when stone size and location are required for management decisions. Use the score to inform shared decision-making about imaging strategy, not to replace clinical judgement.
Disclaimer & References
For Educational Purposes Only. This calculator and the accompanying clinical information are intended as educational tools for healthcare professionals. They do not replace clinical judgement. Results should be interpreted in the full clinical context. Lab reference ranges vary by institution — verify with your own laboratory. Drug dosages should be confirmed against current prescribing information.
References
- Moore CL, Bomann S, Daniels B, et al. Derivation and validation of a clinical prediction rule for uncomplicated ureteral stone — the STONE score: retrospective and prospective observational cohort studies. BMJ. 2014;348:g2191. DOI: 10.1136/bmj.g2191
- Wang RC, Rodriguez RM, Moghadassi M, et al. External validation of the STONE score, a clinical prediction rule for ureteral stone: an observational multi-institutional study. Ann Emerg Med. 2016;67(4):423–432.e2. DOI: 10.1016/j.annemergmed.2015.08.019
- Daniels B, Gross CP, Molinaro A, et al. STONE PLUS: evaluation of emergency department patients with suspected renal colic, using a clinical prediction tool combined with point-of-care limited ultrasonography. Ann Emerg Med. 2016;67(4):439–448. DOI: 10.1016/j.annemergmed.2015.10.020
- Kim B, Kim K, Kim J, et al. External validation of the STONE score and derivation of the modified STONE score. Am J Emerg Med. 2016;34(8):1567–1572. DOI: 10.1016/j.ajem.2016.05.061
- Green SM, Schriger DL. The sinking STONE: what a failed validation can teach us about clinical decision rules. Ann Emerg Med. 2016;67(4):433–436. DOI: 10.1016/j.annemergmed.2015.11.022
- Moore CL, Daniels B, Singh D, et al. Ureteral stones: implementation of a reduced-dose CT protocol in patients in the emergency department with moderate to high likelihood of calculi on the basis of STONE score. Radiology. 2016;280(3):743–751. DOI: 10.1148/radiol.2016151691
- Safaie A, Mahdavi A, Shams-Vahdati S, et al. A clinical prediction rule for uncomplicated ureteral stone: the STONE score; a prospective observational validation cohort study. Turk J Emerg Med. 2019;19(4):148–152. DOI: 10.1016/j.tjem.2019.04.003
- Smith-Bindman R, Aubin C, Bailitz J, et al. Ultrasonography versus computed tomography for suspected nephrolithiasis. N Engl J Med. 2014;371(12):1100–1110. DOI: 10.1056/NEJMoa1404446
- Scales CD, Smith AC, Hanley JM, Saigal CS. Prevalence of kidney stones in the United States. Eur Urol. 2012;62(1):160–165. DOI: 10.1016/j.eururo.2012.03.052