Urinary lactic dehydrogenase as a marker of renal injury in blunt trauma patients with hematuria.

We evaluated the use of urinary lactic dehydrogenase (LDH) in predicting renal injury in a convenience sample of 36 blunt trauma patients with hematuria. The mean +/- SEM urinary LDH for the five patients with renal injuries was 129.4 +/- 35 U/L, which was not significantly different from the mean urinary LDH levels in either the 22 patients without demonstrable genitourinary or retroperitoneal injuries (92.9 +/- 20.7 U/L) or the nine patients with nonrenal genitourinary or retroperitoneal injuries (165 +/- 46 U/L). Urinary LDH at a threshold of 135 U/L was more specific (75% vs 53%, P less than .01) and more accurate (74% vs 57%, P less than .01) than hematuria at a threshold of 50 red blood cells per high-power field in predicting lacerations of the kidney or ureter; urinary LDH was less sensitive than hematuria at these thresholds (67% vs 100%), but not significantly. We conclude that urinary LDH is a nonspecific marker of cellular disruption anywhere along the genitourinary tract in otherwise healthy blunt trauma patients.