phase: to assess for vascular injury and active contrast extravasation2 Nephrographic phase: to demonstrate parenchymal contusions and lacerations
3 Delayed phase: to identify collecting system injury.
In clinical practice, however, whole‐body trauma imaging is often obtained prior to the involvement of the urologist and delayed phase imaging is not routinely performed. As the optimal timing for delayed phase imaging is 9–10 minutes after contrast injection, another CT can be performed without repeat IV contrast injection if performed within this time window [26]. If there is a PRI on initial imaging and delayed phase imaging was not obtained, a repeat CT with delayed phase imaging is still recommended and can be performed with low risk of contrast‐induced nephropathy [27].
The American Association for the Surgery of Trauma (AAST) organ injury scale is the most commonly‐used tool to grade traumatic solid organ injuries. The AAST staging for renal trauma is shown in Table 2.1. Although it was not originally designed to be a prognostic tool, studies have shown good correlation between higher‐grade renal injuries and need for surgical intervention, such as nephrectomy [28, 29].
Findings on CT that are risk factors for hemorrhage and need for urgent invasive intervention are hematoma with a diameter greater than 3.5 cm, medial renal laceration, and intravascular contrast extravasation. In patients with two or more of these risk factors, the risk of intervention to control bleeding was 66.7% [30].
For higher‐grade renal lacerations (Grade IV–V), penetrating trauma, or patients experiencing complications (fever, ileus, etc.), both the AUA and EAU recommend repeat CT imaging two to four days after the initial trauma, because these are prone to developing complications from their initial injury, such as urinoma or persistent bleeding [24, 25].
Management
Non‐Operative
Traditionally, penetrating trauma has been managed with surgical exploration. However, there has been a shift toward more conservative management of trauma patients due to the improvements in imaging, interventional radiology, and resuscitation techniques. For hemodynamically stable patients, NOM with close patient observation should be offered as first‐line therapy [25].
Although there is no consensus algorithm for NOM and there is significant institutional variance, NOM generally comprise of bedrest, strict hemodynamic monitoring in a critical care unit, and serial hematocrit (HCT) checks. If patients are hemodynamically stable with down‐trending HCTs, they should be resuscitated with blood products. The presence of active bleeding on imaging, combined with transfusion requirement or hemodynamic instability, indicate that interventional radiology should be consulted for selective embolization. For patients with urinary extravasation, ureteral stenting should be considered, although optimal timing for stenting (early vs. late) is not currently known. We propose one management strategy in Figure 2.2. NOM, however, should not be equated to non‐interventional management. Rather, NOM should be viewed as an algorithmic approach with stepwise escalation of intervention based on patient dynamics (see Figure 2.3).
For renal injuries, the site of the wound, hemodynamic stability, and diagnostic imaging (grade of injury) are the main determinants for intervention. Although higher‐grade injuries (Grade IV and V) are more likely to require surgical exploration, with careful selection and staging, patients with PRI may be offered a trial of expectant management.
In one series, 54% of stab wounds were successfully managed non‐operatively, with only 3% of patients requiring exploration for delayed bleeding [31]. Another series found that stab wounds were more likely to be successfully managed with NOM if the site of abdominal wound penetration is posterior to the anterior axillary line [32].
PRI from low‐velocity GSWs can be managed with NOM. In one large series, approximately 30% of gunshot PRIs were successfully managed with observation [33]. As there is also a shift toward selective NOM for gunshot abdominal trauma wounds, there may be a larger impetus for NOM in patients with PRI who would not otherwise undergo surgical exploration [34].
Figure 2.2 Proposed Proposed treatment algorithm. CT, computed tomography; HCT, hematocrit; IR, interventional radiology; NOM, non‐operative management; NPO nothing by mouth; PRI, penetrating renal injury.
One quandary has been the management of suspected renal trauma in patients without pre‐operative CT imaging. Data suggests that even if patients are undergoing surgical exploration for associated non‐urologic injuries, renal exploration is not always necessary. The only absolute indication for renal exploration is a pulsatile or expanding retroperitoneal hematoma. Stable retroperitoneal hematomas should not be explored [24]. Obvious urinary leakage from a penetrating mechanism requires evaluation to exclude a renal pelvis or ureteral injury (see Figure 2.4). In one large series of patients undergoing exploratory laparotomy for renal GSWs, 56% of patients did not need renal exploration and renal exploration was associated with a 50% nephrectomy rate [35]. If patients undergo emergent laparotomy without imaging and a stable zone II (retroperitoneal flank) hematoma is not explored, they should receive appropriate renal imaging once stable, in order to evaluate the extent of the injury.
Figure 2.3 Twenty‐one‐year‐old male who sustained a GSW to the abdomen. He had a grade IV right PRI, with injuries to the liver and duodenum. (a) CT demonstrates a significant urine leak on initial delayed phase imaging. (b) He was taken to the operating room for retrograde pyelogram and ureteral stenting. Pyelogram demonstrates contrast extravasation from the middle calyx. Arrow depicts area of contrast extravasation. (c) Repeat CT scan with delayed phase imaging at two weeks demonstrates improved, but persistent contrast extravasation. He was taken to the operating room six weeks after ureteral stenting where retrograde pyelogram demonstrated complete healing of his collecting system and his stent was removed.
Source: courtesy of Jonathan Wingate, MD.
Operative
Operative management of PRI is not as nuanced as NOM – an unstable patient, unresponsive to resuscitation, requires immediate surgical exploration. Surgical exploration is traditionally performed via a midline transabdominal approach. These cases are often performed in conjunction with trauma surgeons, as the rates of concomitant non‐GU organ injuries are very high [8, 36].
Prior to exploring a zone II hematoma, the surgeon should ensure there is a contralateral kidney if no pre‐operative imaging was obtained. This can be performed by manual palpation of the contralateral kidney or a single shot urogram
