A clinical prediction rule for the diagnosis of ureteral calculi in emergency departments

Abstract

Objective: To determine: 1) whether a simple clinical prediction rule could identify emergency department patients with ureteral calculi; 2) whether the kidney, ureter, and bladder (KUB) radiograph provides diagnostic information beyond that obtained from the history and physical examination; and 3) whether ureteral calculi can be diagnosed accurately in the emergency department without emergency excretory urography, commonly known as intravenous pyelography (IVP).

Patients: Two hundred three patients who underwent emergency KUB and IVP studies for nontraumatic abdominal or flank pain (derivation group) were retrospectively identified from radiology department records; 72 patients were prospectively evaluated in the emergency department for suspected ureteral stones (validation group).

Measurements: Clinical information included age, gender, characteristics of pain, associated symptoms, presence of fever, history of ureteral calculi, whether a stone was passed, and results of urinalysis and KUB and IVP studies. All KUB and IVP radiographs were independently reviewed by a radiologist blinded to the patient’s clinical information and urinalysis results.

Design: Stepwise linear discriminant analysis was used to derive a four-item prediction rule from the derivation group and the validation group; the areas under the receiver operating characteristic (ROC) curves and the misclassification rates were compared.

Results: The four-item rule (acute onset, flank pain, hematuria, and positive KUB radiograph) correctly classified 83% of patients in the derivation group and 90% in the validation group. The four-item rule had an ROC area of 0.86 in the derivation group and 0.89 in the validation group. The KUB radiograph significantly improved the discriminant ability of the two history items and the urinalysis result. Thirty-three percent of patients were identified to be in a subset with a 96% probability of having a stone.

Conclusion: These findings, which should be confirmed in another emergency department, suggest that subsets of patients with suspected ureteral calculi may be managed without emergency IVP; this approach thereby reduces the time a patient spends in the emergency department, radiation exposure, expense, and morbidity.