STONE Score for Uncomplicated Ureteral Stone

STONE Calculator

S - Sex

T - Timing (Duration of Pain Onset)

O - Origin (Race)

N - Nausea/Vomiting

E - Erythrocytes (RBCs in Urine)

STONE Score: –

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Predicts likelihood of ureteral stone in nontoxic-appearing patients with flank pain.

Why Use

Kidney stone patients are at significant risk of high lifetime radiation exposure from the diagnosis and treatment of stones. Over 80% of kidney stones pass spontaneously, and immediate CT does not usually change the course of the patient’s disease process. CT may be more appropriate after conservative medical care has failed. This score helps clinicians risk-stratify patients, which can be used to guide diagnostic decision-making and shared decision-making conversations. Performed better than clinician gestalt in validation. High likelihood of kidney stone signifies a low likelihood of a dangerous alternative diagnosis and may allow clinicians to forego immediate CT scan in healthy patients.

When to Use

Patients with suspected kidney stones and normal renal function. Do not use in patients with fever or other signs of infection, recent trauma or urologic surgery, or active malignancy.

Formula

The STONE Score is calculated by the addition of the selected points: Variable Points Sex Male 0 Female 2 Duration of pain prior to presentation >24 hours 0 6-24 hours 1 <6 hours 3 Obvious hematuria No 0 Yes 1 Nausea and vomiting None 0 Nausea alone 1 Nausea and vomiting 2 Erythrocytes No 0 Yes 2

Pearls / Pitfalls

High STONE Scores decrease likelihood of an alternative diagnosis to <2% and therefore those with high STONE Scores could, in the correct clinical context, be managed without an immediate CT. Hydronephrosis on ultrasound, in addition to the score, increases likelihood of kidney stone. Patients who are febrile, elderly, or ill at baseline, or do not clinically improve during their ED stay, are more likely to benefit from a CT scan, regardless of score. The score was not developed to be used for ill-appearing or infected patients. External validation studies suggest that the omission of the “race” criterion may be more accurate in locations with a higher proportion of African-American patients. In this case, a score of 8-10 would be considered “high” ( Wang et al, 2016 ). Per ACEP’s Choosing Wisely , clinicians should avoid ordering CTs in young healthy patients with a history of kidney stones presenting with signs and symptoms of an uncomplicated (noninfected) kidney stone.

Management

A high score can obviate need for an immediate CT scan, in healthy patients. If further imaging is warranted, a low dose CT scan may be more appropriate than a standard dose CT scan in these patients. A moderate score plus a finding of hydronephrosis suggests a high likelihood of a kidney stone and may also obviate the need for immediate CT scan in healthy patients. A low score should cause clinicians to consider alternative diagnoses but does not in itself necessitate a CT scan or other imaging. Over 75% of patients with a low score had non-diagnostic CT scans.

Advice

May be used to facilitate shared decision-making with patients. Daniels et al (2016) showed that: For patients with low and moderate STONE scores, the presence of hydronephrosis on ultrasound increased the likelihood of kidney stone as diagnosis, with moderate/severe hydronephrosis increasing the likelihood more than mild hydronephrosis. For all levels of STONE score, hydronephrosis on ultrasound decreased the likelihood of a dangerous alternative diagnosis, and increased the likelihood of the patient having a urologic procedure within 90 days (total procedure rate: 30%).

More Information

Interpretation: STONE Score Risk Group Likelihood of Ureteral Stone 0 Low 4% 1 7% 2 14% 3 26% 4 Moderate 42% 5 60% 6 76% 7 High 87% 8 93% 9 96% 10 98%