Test characteristics of urinalysis to predict urologic injury in children

Objective: To use receiver operator characteristic curve methodology to determine the test characteristics of microscopic hematuria for identifying urologic injuries in children who underwent computed tomography (CT) of the abdomen and pelvis as part of a trauma evaluation. Methods: We performed a retrospective medical record review of all children from 0 to 12 years of age who presented to our pediatric emergency department within a Level 1 trauma center, had an abdominal and pelvic CT and a microscopic urinalysis as part of an initial evaluation for trauma. Urologic injury was defined as any injury to the kidneys, ureters or bladder. We defined hematuria from the microscopic urinalysis and reported by the clinical laboratory as the exact number of red blood cells per high power field (RBC/hpf). Results: Of the 502 children in the study group, 17 (3%; 95% CI [2%-5.4%]) had evidence of urologic injury on the abdominal or pelvic CT. Microscopic urinalysis for those children with urologic injury ranged from 0 to15,544 RBC/hpf. The remaining 485 children without urologic injury had a range of hematuria from 0 to 20,596 RBC/hpf. A receiver operating characteristic curve was generated and the area under the curve is 0.796 (95% CI [0.666-0.925]). Conclusion: If the abdominal and pelvic CT is used as the criterion standard for identifying urologic trauma, the microscopic urinalysis has moderate discriminatory power to predict urologic injury.