Intravenous urography in the emergency department: when do we need it?

Abstract

Intravenous urography (IVU) is a useful radiographic study in the detection of renal and ureteral calculi. However, it is time consuming, expensive, and exposes the patient to i.v. contrast and radiation. To determine the impact of utilizing IVU less for the detection of renal calculi, criteria for ordering IVU in the emergency department (ED) were evaluated, and patients with high probability of positive IVU were identified. Variables included presence of acute flank pain with haematuria, prior history of renal calculus, degree of haematuria, and uncontrolled pain. We reviewed patients presenting with acute flank and abdominal pain with haematuria from May 1995 to May 1996 at a large urban university hospital. Charts were abstracted for prior history, reason for ordering IVU, time in the ED, laboratory results, IVU result, final diagnosis, and disposition. Data was analysed with Student's t-test, Wilcoxon rank-sum and receiver operating characteristic (ROC) analysis. A total of 302 patients were identified, and 185 underwent IVU during the study period. For patients with prior history of renal calculi 82% had positive IVU (sensitivity 51%, specificity 87%). For patients with both acute flank pain and haematuria, 92% had a positive IVU (sensitivity 93%, specificity 43%), and 19% of patients with abdominal pain of unclear aetiology with haematuria had a positive IVU. All patients with uncontrolled pain had evidence of high-grade obstruction on IVU. Degree of haematuria was not predictive of a positive IVU from ROC curve derivation. IVU is a useful study in the ED but may be overutilized, leading to lengthy patient stays. The combined objective findings of acute flank pain and haematuria are sensitive, and prior history is specific in identifying patients with renal calculi. Degree of haematuria was not useful in predicting renal calculi. By utilizing the criteria of acute flank pain and haematuria as a decision aid, 66% of all IVUs ordered could have been avoided.