Usefulness of Urinalysis in Following Patients With Distal Ureterolithiasis

Abstract

The determine the usefulness of urinalysis in monitoring patients with distal ureterolithiasis. Patients with microhematuria who were found to have a distal ureteral stone and who were candidates for conservative management were enrolled in the study. Patients were typically seen in clinic at 1 to 2 weeks after initial diagnosis and reassessed. A urinalysis, including office dipstick and automated laboratory analysis using the IQ 200 IRIS analyzer, were performed. The absence or presence of microhematuria was determined and compared with results of repeated unenhanced helical CT of the abdomen and pelvis to determine the sensitivity, specificity, and positive and negative predictive values of urinalysis. Twenty-nine patients were enrolled in this prospective study. The mean age of the patients was 43.5 years. The sex distribution was predominantly male, with 72% men and 28% women. Ultimately, 18 patients are included in our analysis with the remainder either lost to follow-up or excluded because of protocol violation. Average distal stone size was 4.1 mm (range 2.0-6.5 mm). Stones were evenly distributed between the right and the left ureters, with 50% on either side. Mean time to follow-up was 18 days with a range of 2 to 63 days. The sensitivity of urinalysis was determined to be 40% (8%-72%) while the specificity was 63% (28%-98%). The predictive value of a positive test was 57% (19%-95%) and the predictive value of a negative test was 55 % (25%-85%). The confidence interval for each of these parameters is inclusive of the value of 50%, indicating that urinalysis is no better than randomness in predicting presence or absence of a stone by CT. The absence or presence of microhematuria does not accurately predict whether a distal ureteral stone has passed or is still present. In those patients who need or want to know whether a stone is still present, unless a stone is strained, we suggest repeated CT imaging.