Prospective Comparison of Microscopic and Gross Hematuria as Predictors of Bladder Injury in Blunt Trauma

Abstract

The evaluation of the genitourinary system in patients with blunt trauma remains controversial. Historically, patients with more than 50 red blood cells on urinalysis underwent additional genitourinary imaging. Retrospective studies have demonstrated that bladder injury is almost always associated with gross hematuria. We have prospectively demonstrated that bladder imaging is required for gross hematuria and unnecessary for microscopic hematuria. Patients sustaining blunt trauma with hematuria were prospectively evaluated during a 3-year period. During the first 18 months of the study (first treatment arm), patients with microscopic hematuria (more than 50 red blood cells on urinalysis) underwent bladder imaging. During the second 18 months, patients underwent bladder imaging only for gross hematuria. A total of 8026 patients were evaluated. In the first arm, 214 patients underwent cystography for microscopic hematuria, and no bladder injuries were identified; 78 patients underwent cystography for gross hematuria, and 21 bladder injuries were identified. Chi-square analysis revealed no difference in the presence of microscopic hematuria to predict for bladder injury. In the second arm, 308 patients presented with microscopic hematuria, none of whom underwent cystography, and 91 patients underwent cystography for gross hematuria, with 15 bladder injuries identified. The presence of gross hematuria demonstrated 100% sensitivity and 98.5% specificity as a screening test for bladder injury. No bladder injuries were missed. The results of our study have shown that the presence of gross hematuria warrants evaluation of the bladder. The presence of gross hematuria demonstrated improved sensitivity, specificity, positive predictive value, negative predictive value, and accuracy over the presence of microscopic hematuria in the detection of bladder injury. Using gross hematuria as an indication for bladder imaging will eliminate unnecessary imaging without compromising the quality of patient care.