Routine follow-up imaging of kidney injuries may not be justified

The purpose of this investigation was to determine the yield of repeat follow-up imaging in patients sustaining renal trauma.

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.

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.

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.