Do we need repeated CT imaging in uncomplicated blunt renal injuries? Experiences of a high-volume urological trauma centre.

Background: Current guidelines recommend repeat computed tomography (CT) imaging in high-grade blunt renal injury within 48-96 h, yet diagnostic value and clinical significance remain controversial. The aim of this work was to determine the possible gain of CT re-imaging in uncomplicated patients with blunt renal trauma at 48 h after injury, presenting one of the largest case series.

Methods: A retrospective database of patients admitted to our centre with isolated blunt renal trauma due to sporting injuries was analysed for a period of 20 years (2000-2020). We included only patients who underwent repeat imaging at 48 h after trauma irrespective of AAST renal injury grading (grade 1-5) and initial management. The primary outcome was intervention rates after CT imaging at 48 h in uncomplicated patients versus CT scan at the time of clinical symptoms.

Results: A total of 280 patients (mean age: 37.8 years; 244 (87.1%) male) with repeat CT after 48 h were included. 150 (53.6%) patients were classified as low-grade (grade 1-3) and 130 (46.4%) as high-grade (grade 4-5) trauma. Immediate intervention at trauma was necessary in 59 (21.1%) patients with high-grade injuries: minimally invasive therapy in 48 (81.4%) and open surgery in 11 (18.6%) patients, respectively. In only 16 (5.7%) cases, intervention was performed based on CT re-imaging at 48 h (low-grade vs. high-grade: 3.3% vs. 8.5%; p = 0.075). On the contrary, intervention rate due to clinical symptoms was 12.5% (n = 35). Onset of clinical progress was on average (range) 5.3 (1-17) days post trauma. High-grade trauma (odds ratio [OR]_{grade 4 vs. grade 3}, 14.62; p < 0.001; OR_{grade 5 vs. grade 3}, 22.88, p = 0.004) and intervention performed at the day of trauma (OR 3.22; p = 0.014) were powerful predictors of occurrence of clinical progress.

Conclusion: Our data suggest that routine CT imaging 48 h post trauma can be safely omitted for patients with low- and high-grade blunt renal injury as long as they remain clinically stable. Patients with high-grade renal injury have the highest risk for clinical progress; thus, close surveillance should be considered especially in this group.