Routine Follow-Up Imaging of Kidney Injuries May Not Be Justified

Background: The purpose of this investigation was to determine the yield of repeat follow-up imaging in patients sustaining renal trauma. Methods: The Los Angeles County + University of Southern California Medical Center trauma registry was reviewed to identify all patients with a diagnosis of kidney injury from 2005 to 2008. All final attending radiologist interpretations and the dates of the initial and follow-up computerized tomography (CT) scans were also reviewed. Grades I, II, and III were grouped as low-grade injuries and grades IV and V as high-grade injuries. Results: During the 4-year study period, 120 (1.2% of all trauma admissions) patients had a total of 121 kidney injuries: 85.8% were male, and the mean age +/- SD was 31.1 years +/- 14.5 years. Overall, 22.6% of blunt and 35.6% of penetrating kidney injuries were high grade (IV-V; p = 0.148). These high-grade injuries were managed operatively in 35.7% and 76.2% of blunt and penetrating injuries, respectively, (p = 0.022). Overall, 31.7% underwent at least one follow-up CT; 24.2% of patients with blunt and 39.7% of patients with penetrating kidney injury, respectively. None of the patients with a low-grade injury managed nonoperatively developed a complication, independent of the injury mechanism. High-grade blunt and penetrating kidney injuries managed nonoperatively were associated with 11.1% and 20.0% complication rate identified on follow-up CT, respectively. For patients who underwent surgical interventions for penetrating kidney injuries, the diagnosis of the complication was made at 9.8 days +/- 7.0 days (range, 1-24 days), with 83.3% of them diagnosed within 8 days postoperatively. The most frequent complication identified was an abscess in the renal fossa (50.0% of all complications). Other complications included urinoma, ureteral stricture, and pseudoaneurysm. All patients who developed complications were symptomatic, prompting the imaging that led to the diagnosis. All patients who developed a complication after a penetrating injury required intervention for the management of the complication. Conclusion: Selective reimaging of renal injuries based on clinical and laboratory criteria seems to be safe regardless of injury mechanism or management. High-grade penetrating injuries undergoing operative intervention should carry the highest degree of vigilance and lowest threshold for repeat imaging.