Detection and significance of microscopic hematuria in patients with blunt renal trauma.

Detection of hematuria is paramount in establishing injury to the urinary system. In 339 patients with blunt renal trauma in whom radiographic studies defined the severity of injury we compared the degree of microscopic hematuria determined by dipstick and microscopic urinalysis. The overall correlation between the 2 methods was low (Pearson's coefficient 0.41). However, more than 80 per cent of the urine samples with 50 to 100 red blood cells per high power field corresponded to a dipstick result of 3+. The dipstick method had greater than 97.5 per cent sensitivity and specificity for detection of microscopic hematuria. Only 7 of the 339 patients (less than 2 per cent) had a discharge diagnosis of other than renal contusion: 5 had renal artery thrombosis or avulsion of the renal vessels and 2 had minor cortical lacerations that were managed nonoperatively. Although microscopic hematuria may be quantified more accurately by microscopic analysis, it can be detected reliably with a high degree of sensitivity and specificity by dipstick analysis.