Brewer ME et al. (2007) Prospective comparison of microscopic and gross hematuria as predictors of bladder injury in blunt trauma. Urology 69: 1086–1089

Abdominal injuries have high associated mortality, making early diagnosis and timely treatment essential. Traditionally, radiographic investigation for bladder injury has followed detection of microscopic and gross hematuria, but this approach can delay therapy. Retrospective studies have suggested a strong association only between gross hematuria and bladder injury. Brewer et al., therefore, prospectively tested the relation between type of hematuria and prediction of bladder injury.

Patients presenting to one center with blunt trauma were assessed. For the first 18 months of the study cystography was performed if microscopic (>50 red blood cells per high-powered field) or gross hematuria (>50 red blood cells per high-powered field plus visible blood in catheter-drained urine) were detected. For the latter 18 months only patients with gross hematuria underwent cystography, and patients with microscopic hematuria were observed.

In total, 691 patients underwent cystography. Of these, 78 (27%) of 292 in the first 18 months had gross hematuria, as did 91 (23%) of 399 in the second 18 months, among whom trauma-related bladder injury was identified in 21 and 15, respectively. No bladder injuries were found among patients with microscopic hematuria and none was missed among observed patients. Sensitivity and specificity for gross hematuria to predict bladder injury were 100% and 98.5%, and negative predictive value was 100%.

The authors support avoiding radiography in patients with only microscopic hematuria. They believe this approach will reduce the rate of unnecessary investigations and delays to treatment.