Introduction

The AUA convened a Practice Guideline Panel in 2014 to synthesize the most relevant and up-to-date evidence and compose its Urotrauma Guideline¹ to guide clinicians in the appropriate methods of evaluation and management of genitourinary injuries. Shortly after these guidelines were released, the National Academies of Science, Engineering, and Medicine (NASEM) published its landmark 2016 report, A National Trauma System: Integrating Military and Civilian Trauma Systems to Achieve Zero Preventable Deaths after Injury.² This document called upon a broad multidisciplinary group of trauma professionals and laid out an ambitious roadmap to achieve zero preventable injury deaths. The American College of Surgeons Committee on Trauma (COT) created its Zero Preventable Deaths and Disability initiative³ and developed 4 workgroups focused on trauma system infrastructure/governance; research funding and direction; data linkage, integration, and outcome measures; and military/civilian trauma workforce training and readiness.

As urologists committed to reducing preventable death and disability from genitourinary injuries, we interpret the work of NASEM and COT as trying to save the lives of all renal trauma patients that can be saved. High-grade renal injuries exert morbidity and mortality through acute hemorrhage, loss of functioning nephrons, and complications, including delayed bleeding, infection, urine leak, and hypertension.¹ Fortunately, appropriate imaging accurately stages renal injuries, allowing trauma surgeons and urologists to make decisions about the immediate and long-term course of action for a given mechanism of injury and overall trauma scenario.

Renal injuries are graded according to the Organ Injury Scale of the American Association for the Surgery of Trauma (AAST).⁴ The majority of injuries are due to blunt trauma, although, stage for stage, outcomes are comparable between penetrating and blunt mechanisms. Figure 1 shows the 5 grades of renal injury and the heterogeneity of mechanisms that can lead to parenchymal, vascular, and collecting system trauma to the kidney.

In addition to guideline statements, the AUA highlighted the management of high-grade renal trauma at the 2024 Annual Meeting. The Plenary Program on the topic focused on 3 important concepts: quantifying risks of bleeding that require intervention with angioembolization (AE) and/or surgery; the challenge of immediate renal exploration without full staging; and predicting and managing the delayed complications of renal injury.

Risk Stratification and Nonoperative Management of Renal Trauma

Renal trauma is increasingly managed without surgical intervention, with modern estimates suggesting over 80% of patients with high-grade renal trauma are treated nonoperatively.^5,6 Penetrating injuries to the retroperitoneum have traditionally been managed with urgent exploration.⁷ However, in accordance with the overall trend toward conservative management, data suggest that a stable patient can be observed for 24 to 48 hours with close monitoring and serial imaging in over 90% of patients with penetrating renal injuries.⁸

Reserving operative intervention for only those patients showing signs of instability was codified succinctly in statement 4 of the 2020 update to the AUA Urotrauma Guideline: “In hemodynamically stable patients with renal injury, clinicians should use non-invasive management strategies” (Figure 2).¹ In addition to hemodynamic stability, efforts are continually underway to further help clinicians identify patients at the highest risk for bleeding and the highest need for intervention. Recent evidence from the National Trauma Databank and the Multi-Institutional GenitoUrinary Trauma Study suggests that even a subset of the AAST grade V patients can be successfully managed without operative intervention, highlighting how AAST injury grading is an incomplete tool for predicting intervention.^9,10 To address this, the Multi-Institutional GenitoUrinary Trauma Study has proposed a validated predictive nomogram for bleeding intervention amongst renal trauma patients (Figure 3).¹¹

In the continued effort for renal preservation in the face of active bleeding, trauma providers have increasingly turned toward AE with success rates of ~85% even in high-grade trauma.^12,13 Limited data even support possible superiority to AE over surgical repair in avoiding nephrectomy.¹² Crucially, many of the indicators for intervention are predictors of AE failure—namely, vascular contrast extravasation and hemodynamic instability.¹³ While AE can be safely repeated in the event of a failure, providers should remain wary of the need for surgical intervention for patients with AAST grade V injury, urinary or contrast extravasation, and hemodynamic instability.

Challenges of Immediate Renal Exploration

While evidence-based guidelines and surgical principles direct the management of high-grade renal trauma, intraoperative clinical conundrums will arise. This is of particular importance when preoperative imaging for staging (eg, CT scan) is not obtained. The urologist consulted intraoperatively for surgical repair or exploration without prior CT imaging may use an on-table intravenous pyelogram (IVP) to determine the presence of a contralateral, functioning kidney.¹ Use of IVP outside of this indication is not recommended as it does not influence the decision for exploration.¹⁴ If the IVP is not feasible to obtain, palpating the contralateral kidney aids in confirming the presence of the organ but, of course, can not confirm its function. Another challenging intraoperative conundrum is a nonexpanding retroperitoneal hematoma. In an unstable patient, regardless of whether the hematoma is expanding, surgical exploration is warranted.¹ How this is achieved is surgeon dependent, but early transmesenteric vascular control does not improve nephrectomy rate or blood loss.¹⁵ In a stable patient, retroperitoneal exploration should be avoided as the nephrectomy rate is > 10%.¹⁶

Guiding clinical principles of collaboration with trauma surgery, early communication, serial patient examinations, and a low threshold for reimaging/intervention will lead to improved outcomes for any clinical conundrum of renal trauma.

Long-Term Complications of Renal Exploration for Trauma

With best practices moving toward conservative management/observation, many renal trauma patients can avoid open kidney surgery and preserve partial or even full function of the injured renal unit. This aligns with the work of NASEM and COT as trying to save all lives that can be saved while also preventing renal unit loss. Nevertheless, complications from high-grade renal trauma still arise even after the acute bleeding has been controlled.

Complications due to renovascular or collecting system injury include hypertension, pseudoaneurysm formation, and urine leak, which can result in a symptomatic urinoma.¹⁷ For patients who develop renin-mediated hypertension following their renal trauma, the preferred management is oral antihypertensive medication.¹⁸ In rare cases surgery is needed to evacuate the hematoma that is compressing the renal parenchyma (Page kidney)¹⁹ or nephrectomy for chronic scarring or renovascular hypertension due to arterial stenosis (Goldblatt kidney). Pseudoaneurysms may arise and can become symptomatic, presenting with gross hematuria. Patients who have delayed gross hematuria after renal trauma need imaging and AE if a pseudoaneurysm is present.²⁰ A high rate (80%-90%) of urine leaks heal on their own even in cases where temporary drainage is needed, but some can persist and may lead to a protracted convalescence and potentially delayed nephrectomy (Figures 3 and 4).^21,22 The occasional patient who would have potentially benefited from a nephrectomy at the time of their initial presentation but was committed to months with stents and drains and a nonhealing collecting system calls for further research into patient selection for nonoperative management. The optimal management of urinary extravasation remains an open clinical question and a ripe area for research. Clinically applicable questions include the timing of follow-up imaging, the role of ureteral stenting, and predictors of complications from the collecting system injury.

Conclusions

As a result of higher levels of evidence developed subsequent to the initial release of the AUA Urotrauma Guideline, bleeding risk for renal trauma can be quantified and effectively controlled with interventional radiology and/or surgery. A persistent challenge for trauma surgeons and urologists is when immediate exploration without full radiographic staging requires an on-table decision regarding whether to explore the kidney, with associated higher rates of nephrectomy, or close the patient and image postoperatively. Finally, the absence of robust predictors of postoperative complications remains a key gap in knowledge that can be addressed in future larger-scale studies.