Background
The kidney is the most common organ within the genitourinary system to be injured during trauma and occurs in 8–10% of patients with abdominal injuries [
1]. Blunt renal trauma is usually caused by sudden deceleration, leading to contusion or laceration of the renal parenchyma. Increasing recreational activities in our alpine region such as skiing and mountain biking lead to even more frequent blunt trauma accidents. With nearly 50 million tourist nights spent per year and several referring hospitals in the region, the Medical University Hospital of Innsbruck stands as a high-volume level 1 trauma centre in the central alpine region. We already shared data of our experience with blunt renal trauma in children with one of the largest cohorts known [
2]. The American Association for the surgery of trauma (AAST) has implicated a radiological globally applied classification to define grades 1–5 of renal trauma [
3]. In the past few years, a switch from primary surgical interventions to a more conservative approach has been generally observed [
4]. Whereas low-grade trauma has always primarily been assigned to non-operative management, high-grade kidney injuries were often directly forwarded to immediate surgical intervention. In the past years, non-operative management including minimally invasive interventions such as stenting due to urinoma formation or angiographic coiling to control bleeding has become the established gold standard and treatment of choice for all haemodynamically stable patients, regardless of their primary injury grade [
5‐
8].
Management and clinical utility of repeat routine imaging in high-grade (grade 4 and 5) renal trauma remains a very controversial issue in current literature and data are lacking. Up to now, case series in adults use CT to follow-up renal trauma, although already in 2009, ultrasonography (US) was confirmed to be an efficient alternative modality to monitor blunt trauma in a paediatric cohort [
2,
9]. Whereas current EAU Guidelines on Paediatric Urology recommend a close follow-up with ultrasound 48 to 72 h after the initial CT scan in stable patients irrespective of trauma severity [
10,
11], the Guidelines of the American Urological Association (AUA) and the European Association of Urology (EAU) recommend early repeat imaging in high-grade injury within two to four days after trauma to minimize the risk of missed complications [
6,
12]. In patients with low-grade (grade 1 to 3) renal trauma, repeat CT imaging can be omitted as long as no symptoms occur according to current guidelines [
1]. However, these recommendations are based on a retrospective series from 2010 with 138 patients undergoing conservative treatment and repeat routine imaging more than 48 h after trauma [
13]. A few studies already gave first evidence that repeat CT imaging in uncomplicated also high-grade injuries is not justified [
13,
14]. Data of larger cohorts to emphasize this retaining patient management is yet lacking.
In addition to the now well-established conservative management without the occurrence of any unnecessary surgical complications, potential danger of the radiation exposure must also be considered when routinely performing CT scans without an absolute indication especially in young people. Risk of carcinogenic effects of CT is assumed to be small for an individual patient [
15], yet one should also review the risk in terms of the trauma patient population. Concerns about carcinogenic risks have already encouraged attempts to reduce CT imaging when not inevitably necessary [
16,
17].
Our study presents the largest described case series of isolated blunt renal trauma patients with routine follow-up CT imaging 48 h post trauma. The aim of the study was to assess the diagnostic value and clinical utility with regard to intervention rates of routine repeat control CT imaging in uncomplicated patients with blunt renal trauma 2 days post trauma in comparison to CT control at the time of clinical symptoms (clinical progress).
Results
Two-hundred and eighty patients were admitted at our department due to isolated blunt renal trauma with repeat CT imaging after 48 h from 2000 to 2020. The mean (range) age was 38.1 (18–78) years. Of these, 87.1% (n = 244) were male. Renal trauma was classified as follow: 7 (2.5%) grade 1, 50 (17.9%) grade 2, 93 (33.2%) grade 3, 119 (42.5%) grade 4 and 11 (3.9%) grade 5. Thus, 150 (53.6%) patients were classified as low-grade trauma and 130 (46.4%) as high-grade injury.
Baseline characteristics
Mean (range) time of inpatient stay was 8.5 (3–30) days, with a statistically significant longer stay for high-grade trauma patients (mean 10.6 days) than in low-grade trauma (mean 6.6 days, p < 0.001). On time of admission, mean baseline haemoglobin level on trauma day was 12.1 g/dl, with a significant difference between the low-grade (13.2 g/dl) and high-grade trauma (11.0 g/dl, p < 0.001) group. Baseline creatinine levels at trauma day were 0.98 mg/dl in low-grade and 1.05 mg/dl in high-grade traumata (p = 0.021). Analysis showed no differences concerning presence of macrohaematuria at trauma between the two groups, thus being not predictive for high-grade renal injury. Moreover, gross haematuria at trauma was not an independent prognostic factor for clinical progress in the further course (odds ratio [OR] 2.32; p = 0.127). None of the patients needed haemofiltration at any time and none of the patients died. Clinical progress was—unsurprisingly—significantly more frequent in high-grade renal injuries, 2.0% (n = 3) in low-grade and 24.6% (n = 32) in high-grade injuries (p < 0.001). Of important note is that clinical progress after trauma occurred after a mean (± SD) period of 5.3 (± 4.1) days with no significant difference between both groups (low-grade vs. high-grade: 6.7 vs. 5.2; p = 0.561).
Intervention rates
Overall intervention rate at any time was 36.1% (n = 101) with a significant higher rate in high-grade compared to low-grade injuries (72.3% vs. 4.7%; p < 0.001), respectively. Focusing on the day of trauma, 59 (21.1%) patients with high-grade trauma needed immediate interventions. Of these 81.4% (n = 48) could be managed via minimally invasive surgery (ureteral stenting in 30 patients and selective angioembolization in 18 patients), the remaining 18.6% (n = 11) underwent open surgery, of which nine (81.8%) grade 5 injuries required immediate nephrectomy. Overall nephrectomy rate was 3.9% (n = 11), including also 2 patients at the time of clinical progress. All patients with nephrectomy were classified as grade 5 vascular renal trauma.
In only 5.7% (n = 16) cases, intervention was performed based on repeat CT imaging 48 h after trauma. Among these, five were (3.3%) low-grade and 11 (8.5%) high-grade injuries (p = 0.075). Most patients (73.7%) were treated with minimally invasive procedures including ureteral JJ stent due to expanding urinoma (n = 8) and selective angioembolization (n = 3) due to pseudo-aneurysm. In four patients, we decided to perform open renal reconstruction to due expanding urinoma based on renal pelvis rupture. Patient history confirmed existing ureteropelvic junction (UPJ) obstruction in all 4 patients.
On the contrary, intervention rate due to clinical symptoms or laboratory alterations was higher with 12.5% (
n = 35) and onset of clinical symptoms, such as fever, macrohaematuria, haemodynamic instability or flank pain was on average 5.3 days post injury. In detail, whereas all low-grade trauma patients (
n = 3) received minimally invasive therapy, 12 (37.5%) of 32 high-grade trauma patients were referred to open surgery. Although the rate of open surgery in high-grade trauma was similar between CT control 48 h post trauma (36.4%) and at clinical progress (37.5%), nephrectomy rate was higher at clinical progress (16.6% vs. 0%), Table
1.
Table 1
Descriptive patient characteristics of the study population
Injury grade, n (%) | | | | – |
1 | 7 (2.5%) | 7 | – |
2 | 50 (17.9%) | 50 | – |
3 | 93 (33.2%) | 93 | – |
4 | 119 (42.5%) | – | 119 |
5 | 11 (3.9%) | – | 11 |
Age [years], mean (SD) | 38.1 (18.0) | 38.1 (16.9) | 38.2 (19.3) | 0.945 |
Male sex, n (%) | 244 (87.1%) | 129 (86.0%) | 115 (88.5%) | 0.594 |
Inpatient stay [days], mean (SD) | 8.5 (5.1) | 6.6 (3.9) | 10.6 (5.4) | < 0.001 |
Intervention (overall), n (%) | 101 (36.1%) | 7 (4.7%) | 94 (72.3%) | < 0.001 |
Intervention (trauma day), n (%) | 59 (21.1%) | 0 (0.0%) | 59 (45.4%) | < 0.001 |
Severity of intervention (trauma day) | | | | – |
Minimal-invasive | 48 (81.4%) | – | 48 (81.4%) |
Open | 11 (18.6%) | – | 11 (18.6%) |
Clinical progress | 35 (12.5%) | 3 (2.0%) | 32 (24.6%) | < 0.001 |
Severity of intervention (clinical progress) | | | | 0.536 |
Minimal-invasive | 23 (65.7%) | 3 (100.0%) | 20 (62.5%) |
Open | 12 (34.3%) | 0 (0.0%) | 12 (37.5%) |
Time of clinical progress after trauma [days], mean (SD) | 5.3 (4.1) | 6.7 (3.5) | 5.2 (4.2) | 0.561 |
Intervention (CT control 48 h), n (%) | 16 (5.7%) | 5 (3.3%) | 11 (8.5%) | 0.075 |
Severity of intervention (CT 48 h) | | | | 0.516 |
Minimal-invasive | 11 (73.3%) | 4 (100.0%) | 7 (63.6%) |
Open | 4 (26.7%) | 0 (0.0%) | 4 (36.4%) |
Creatinine [mg/dl] at trauma day, mean (SD) | 1.01 (0.22) | 0.98 (0.21) | 1.05 (0.24) | 0.021 |
Hb [mg/dl] at trauma day, mean (SD) | 121.4 (23.3) | 131.6 (17.6) | 109.6 (23.6) | < 0.001 |
Macrohaematuria at trauma, n (%) | 148 (52.9%) | 75 (50.0%) | 73 (56.2%) | 0.338 |
In a multivariate logistic regression model, grade 4 trauma (OR
grade 4 vs. grade 3, 14.62; 95% confidence interval [CI]: 4.16–51.38;
p < 0.001), grade 5 renal trauma (OR
grade 5 vs. grade 3, 22.88; 95% CI: 2.73–191.54;
p = 0.004) and intervention at trauma day (OR, 3.22; 95% CI: 1.27–8.15;
p = 0.014) were found to be independent predictive factors for clinical progress, Table
2.
Table 2
Multivariate logistic regression analysis to predict clinical progress
Age (per one-year increase) | 1.001 | 0.980–1.022 | 0.934 |
Sex (male vs. female) | 0.851 | 0.246–2.951 | 0.800 |
Gross haematuria (yes vs. no) | 0.510 | 0.214–1.212 | 0.127 |
Severity of trauma | | – | 0.001 |
Grade 4 (vs. Grade 3) | 14.624 | 4.162–51.384 | < 0.001 |
Grade 5 (vs. Grade 3) | 22.878 | 2.733–191.536 | 0.004 |
Intervention at trauma day (yes vs. no) | 3.219 | 1.271–8.149 | 0.014 |
Discussion
To our best knowledge, we present the largest cohort with routine CT imaging 48 h after blunt renal trauma in uncomplicated patients. Collision and deceleration trauma mechanisms often result in isolated laceration and contusion of the kidney, with 47% (
N = 150) of trauma resulting in high-grade renal traumata in our cohort. Of these, 45.4% required immediate intervention, 81.4% of which were minimal-invasive interventions and 18.6% of which required open surgery at the day of trauma. In the past decades, there has been a paradigm shift concerning the management of high-grade renal trauma from immediate open surgical exploration to minimally invasive management. However, no prospective randomized controlled trial or systemic review compared effectiveness of conservative and surgical management in high-grade renal trauma; thus, level of evidence is low [
20]. Nevertheless, there are only a few absolute indications for immediate surgical intervention, the majority can be successfully managed non-operatively [
21]. In our cohort, the rate of immediate intervention at trauma day was 21.1% affecting only high-grade renal injuries. The primary AAST classification additionally has been shown to be predictive for the need of surgical intervention [
22,
23] and there is mounting evidence that standardized routine re-imaging in the absence of clinical symptoms or changed laboratory findings has little impact on decision-making regarding intervention or clinical outcome [
24] even in high-grade injuries [
25].
Concerning follow-up, the SIU guidelines recommend repeat CT 36–72 h after a grade 4 injury with damage to the collecting system (Grade C, SIU), [
26]. The AUA guidelines also recommend follow-up imaging for high-grade injuries at 48 h (Grade C, AUA) [
5] and the EAU guidelines on day two to four after trauma in high-grade injuries [
1]. The rationale for repeat imaging until today is early identification and treatment of complications. Literature has already proposed a solely selective approach to reimaging for even high-grade blunt renal trauma only in patients with clinical symptoms [
14]. It was also shown that intensive reimaging of grade 3 and 4 renal injuries did not alter clinical decision making [
25].
In our cohort, overall intervention rate based on repeated CT imaging in asymptomatic patients was very low with 5.7% and independent of the severity of renal trauma (low-grade 3.3% vs. high-grade 8.5%). In most patients (73.3%), minimally invasive management was sufficient. Moreover, 80% of patients were treated due to expanding urinoma. One can of course argue here that based on the asymptomatic status a conservative therapeutic strategy would also have been possible, decreasing the intervention rate at 48 h to 1.1% (
n = 3 with angioembolization due to pseudo-aneurysm). In line with our results, a French multicentric study including 927 patients presented that systemic repeated imaging following renal trauma changed the therapeutic management in only 5.1% of asymptomatic patients [
27]. We therefore conclude that routine imaging also for high-grade renal injuries in the absence of any clinical symptoms or clinical findings is likely unnecessary.
Onset of clinical symptoms was on average seen on day five to six post trauma. Concluding, this would mean that after routine CT after 48 h or even, as recommended by the EAU [
1,
6], AUA [
5] and SIU [
26], after the latest four days, the patient would need another obligate CT with accompanying radiation dosage when acute symptoms occur. Two studies with a cohort size of up to 218 patients reported on selection of repeat CT imaging guided not by trauma grading but rather based on the presence of urine extravasation in addition to clinical and laboratory criteria [
28] and have shown that selective reimaging of renal injuries based on clinical and laboratory criteria would have detected all complications [
24]. In our study, intervention after imaging due to onset of clinical symptoms was observed in 12.5% of patients and had a higher rate of open surgery (37.5%) and nephrectomy (16.6%), leading to the conclusion that patients who really had a clinical need for a CT were the ones who received it. Two studies also strengthen our argument by already showing that routine reimaging after 48 h without a clinical indication was narrowly beneficial and contributed to change the treatment in less than 1%, proposing to omit repeat imaging in the absence of symptoms [
13,
14]. Loftus et al
. stated that individuals with grade IV trauma who received routine CT follow-up imaging were more likely to undergo an operation in the absence of symptoms and received more radiation during their hospital stay. Additionally, in line with our data, reimaging was not associated with an increase in urological complications [
29]. By selective choice in the use of CT, one would not only contribute to a health system cost reduction, but also to a reduction in radiation exposure when considering long-term risks associated with CT in trauma imaging in young patients [
30,
31]. There is a proposal for haemodynamically stable but symptomatic patients to use ultrasound (US) for first evaluation and to proceed to a CT only when US remains inadequate [
24], based on the fact that significant urinomas can be sufficiently detected by US as already shown in a children cohort [
9]. Here it is of notice that US achieves better diagnostics in children due to their physical constitution, yet it may be used as method of choice also in follow-up evaluation in adult patients with renal injuries.
Several limitations must be mentioned. The major limitation of our study includes the retrospective, single-centre study design, which limits statistical power. In addition, no control group (blunt renal trauma without repeat CT imaging at 48 h) was included, so we have no head-to-head comparison. Our findings, however, imply that routine CT re-imaging at 48 h can be safely omitted not only in uncomplicated low-grade, but also in high-grade renal trauma patients.
In conclusion, our cohort demonstrates that high-grade renal trauma and presence of intervention on the day of trauma are independent factors in predicting clinical progression. Importantly, macrohaematuria at baseline did not correlate with the grade of injury and was not an important predictive factor of further clinical progression. It is yet important to note that patients with high-grade blunt injury remain at a high risk for clinical progress; thus, close surveillance including lab tests and sonography is recommended in this subgroup. We therefore propose that clinical symptoms (fever, flank pain, haemodynamic instability) and laboratory results, such as decreasing haemoglobin or elevating creatinine should guide the decision to perform repeat CT imaging. Based on our data, we conclude that current recommended repeat CT imaging does not predict clinically necessary interventions and can be omitted in both low- and high-grade patients without clinical symptoms indicative of worsening conditions.
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