Genitourinary tract injuries

Kidney trauma

Incidence and mechanisms of injury

At most urban trauma centers, mechanisms of kidney injuries are predominantly blunt (80%–90%) and uncommonly penetrating (10%–20%). The kidney is injured in up to 5% of all trauma cases. Children are more likely to sustain a blunt renal injury owing to the relatively large size of the kidney, scant perirenal fat, fetal lobulations, and incomplete rib ossification. The majority of renal injuries are minor and heal spontaneously. Significant kidney injuries occur in only 4% of blunt trauma yet up to 70% of penetrating renal injuries.

Diagnosis

Signs and symptoms

Hematuria is the hallmark of renal injury. The degree of hematuria often does not correspond or predict the extent of renal injury. Up to 40% of renal pedicle injuries present with no hematuria. A history is obtained to quantify the forces involved in the renal injury. Falls from a height and injuries due to high-speed motor vehicle crashes imply deceleration injury and require evaluation of the renal pedicle and ureteropelvic junction (UPJ). Patients with trauma to the flank, abdomen, or lower chest; flank ecchymosis or tenderness; low posterior rib fractures; or lumbar transverse process fractures should be suspected of having a renal injury—and thus should undergo imaging. A major renal injury that results from a minor mechanism usually occurs in a congenitally abnormal kidney (such as UPJ obstruction).

For gunshot wounds (GSWs) to the kidney, it is important to determine if the injury is due to a high- or low-velocity missile. High-velocity missiles usually cause extensive kidney injury and delayed necrosis. The entrance and exit wounds should be marked with radiopaque markers. Stab wound (SW) entrance sites posterior to the anterior axillary line and above the nipple line are less likely to have associated intraperitoneal organ injury or warrant abdominal exploration.

Imaging

Indications for imaging a suspected kidney injury are as follows:

1.
Blunt trauma and gross hematuria
2.
Blunt trauma, microscopic hematuria (>5 red blood cells per high-power field [RBCs/HPF]), and shock (systolic blood pressure < 90 mm Hg)
3.
Major acceleration or deceleration mechanism of injury
4.
Microscopic or gross hematuria after penetrating flank, back, or abdominal trauma or when the missile path is in line with the kidney
5.
Pediatric blunt trauma patient with >50 RBCs/HPF hematuria
6.
Associated injuries/physical signs suggesting underlying renal injury

In unstable patients who require abdominal exploration, prior to any exploration of a retroperitoneal (perirenal) hematoma, it is important to assess the function of the contralateral kidney, in order to avoid removing a solitary kidney. Removing a solitary kidney will render the patient anephric and dialysis dependent. Opening up a retroperitoneal hematoma for high-grade renal injuries risks release of the tamponade effect of Gerota’s fascia, and thus often results in uncontrolled bleeding, and thus by default, a trauma nephrectomy. Practically, the one-shot intravenous urogram (IVU) is often “fuzzy” and difficult to interpret, with up to a 75% false-negative rate. Thus, we do not advocate using the one-shot IVU, but rather to palpate the contralateral side for kidney presence or administer intravenous methylene blue or indigo carmine and temporarily occlude the ipsilateral ureter. Blue urine in the Foley bag indicates a functional contralateral kidney.

Two-phase abdominal computed tomography (CT) with intravenous contrast (arterial and nephrographic) is the imaging study of choice for demonstrating renal parenchymal injury, perirenal or retroperitoneal hematomas, urinary extravasation, injuries to the renal hilum and great vessels, and associated intra-abdominal organ injuries ( Fig. 1 .) Renal artery occlusion and renal infarct are noted by lack of parenchymal enhancement or by a “cortical rim sign.” The cortical rim sign is kidney capsule enhancement, but no parenchymal enhancement. Here the renal artery is thrombosed but the capsule lights up by capsular arteries from the aorta. An arteriographic phase (to assess major vessel injury) and a delayed nephrographic phase (to assess for contrast extravasation) are essential to accurately stage the kidney injury.

FIGURE 1, CT of the abdomen with IV contrast, with delayed images noting contrast extravasation (arrow) and parenchymal laceration = grade 4 kidney injury. Note small and atrophic left kidney.

Ultrasonography (US) is primarily used in Europe for evaluating renal trauma but is of limited value. In general, US is effective in detecting intra-abdominal free fluid, but has low sensitivity and specificity in kidney trauma. At times, US can demonstrate perirenal fluid collections, but cannot distinguish fresh blood from extravasated urine. Arteriography and superselective embolization have important roles in the evaluation and treatment of a contrast “blush” noted on CT or delayed renal bleeding (pseudoaneurysms, arteriovenous fistulas, etc.). Large perirenal hematoma (width > 4 cm) and contrast blush (intravascular contrast extravasation) and medial renal laceration with contrast extravasation are clear indications for urgent intervention—either by angiography and selective embolization or surgical exploration ( Fig. 2 ). Having two or more of the previous criteria results in high nonoperative management (NOM) failure. For NOM of kidney trauma, routinely repeating a CT at 48 to 72 hours after injury is often unnecessary, unless the patient is symptomatic (fever, abdominal pain, change in examination, etc.). In very select cases, arteriography and endoluminal stent placement have also been successful in managing renal artery intimal tears and thrombosis from blunt trauma.

FIGURE 2, (A) Transverse and (B) sagittal CT imaging of grade 5 shattered kidney with large perinephric hematoma (arrows) and multiple deep parenchymal lacerations. Management = nephrectomy.

Stage of injury

Tables 1 to 3 provide detailed injury scoring scales for genitourinary trauma ( https://www.aast.org/resources-detail/injury-scoring-scale ).

TABLE 1

Kidney Injury Scale

AAST Grade *	AIS Severity	Imaging Criteria (CT Findings)	Operative Criteria	Pathologic Criteria
I	2	Subcapsular hematoma and/or parenchymal contusion without laceration	Nonexpanding subcapsular hematoma Parenchymal contusion without laceration	Subcapsular hematoma or parenchymal contusion without parenchymal laceration
II	2	Perirenal hematoma confined to Gerota fascia Renal parenchymal laceration ≤1 cm depth without urinary extravasation	Nonexpanding perirenal hematoma confined to Gerota fascia Renal parenchymal laceration ≤1 cm depth without urinary extravasation	Perirenal hematoma confined to Gerota fascia Renal parenchymal laceration ≤1 cm depth without urinary extravasation
III	3	Renal parenchymal laceration >1 cm depth without collecting system rupture or urinary extravasation Any injury in the presence of a kidney vascular injury or active bleeding contained within Gerota fascia	Renal parenchymal laceration >1 cm depth without collecting system rupture or urinary extravasation	Renal parenchymal laceration >1 cm depth without collecting system rupture or urinary extravasation
IV	4	Parenchymal laceration extending into urinary collecting system with urinary extravasation Renal pelvis laceration and/or complete ureteropelvic disruption Segmental renal vein or artery injury Active bleeding beyond Gerota fascia into the retroperitoneum or peritoneum Segmental or complete kidney infarction(s) due to vessel thrombosis without active bleeding	Parenchymal laceration extending into urinary collecting system with urinary extravasation Renal pelvis laceration and/or complete ureteropelvic disruption Segmental renal vein or artery injury Segmental or complete kidney infarction(s) due to vessel thrombosis without active bleeding	Parenchymal laceration extending into urinary collecting system Renal pelvis laceration and/or complete ureteropelvic disruption Segmental renal vein or artery injury Segmental or complete kidney infarction(s) due to vessel thrombosis without active bleeding
V	5	Main renal artery or vein laceration or avulsion of hilum Devascularized kidney with active bleeding Shattered kidney with loss of identifiable parenchymal renal anatomy	Main renal artery or vein laceration or avulsion of hilum Devascularized kidney with active bleeding Shattered kidney with loss of identifiable parenchymal renal anatomy	Main renal artery or vein laceration or avulsion of hilum Devascularized kidney Shattered kidney with loss of identifiable parenchymal renal anatomy

Vascular injury is defined as a pseudoaneurysm or arteriovenous fistula and appears as a focal collection of vascular contrast that decreases in attenuation with delayed imaging. Active bleeding from a vascular injury presents as vascular contrast, focal or diffuse, that increases in size or attenuation in delayed phase. Vascular thrombosis can lead to organ infarction.

Grade based on highest grade assessment made on imaging, at operation or on pathologic specimen.

More than one grade of kidney injury may be present and should be classified by the higher grade of injury.

* Advance one grade for multiple injuries up to grade III.

TABLE 2

Ureter Injury Scale

Grade *	Type of Injury	Description of Injury	ICD-9	AIS-90
I	Hematoma	Contusion or hematoma without devascularization	867.2/867.3	2
II	Laceration	< 50% transection	867.2/867.3	2
III	Laceration	⩾ 50% transection	867.2/867.3	3
IV	Laceration	Complete transection with < 2 cm devascularization	867.2/867.3	3
V	Laceration	Avulsion with > 2 cm of devascularization	867.2/867.3	3

* Advance one grade for bilateral up to grade III.

TABLE 3

Bladder Injury Scale

Grade *	Injury Type	Description of Injury	ICD-9	AIS-90
I	Hematoma	Contusion, intramural hematoma	867.0/867.1	2
	Laceration	Partial thickness		3
II	Laceration	Extraperitoneal bladder wall laceration <2 cm	867.0/867.1	4
III	Laceration	Extraperitoneal (⩾2cm) or intraperitoneal (<2cm) bladder wall laceration	867.0/867.1	4
IV	Laceration	Intraperitoneal bladder wall laceration >2cm	867.0/867.1	4
V	Laceration	Intraperitoneal or extraperitoneal bladder wall laceration extending into the bladder neck or ureteral orifice (trigone)	867.0/867.1	4

* Advance one grade for multiple lesions up to grade III

Management

Figure 3 offers a treatment algorithm for renal trauma. Blunt renal injuries are almost all managed conservatively. In hemodynamically stable or stabilized patients, in order to select NOM, CT imaging that accurately portrays American Association for the Surgery of Trauma stages (grades) the kidney injury and associated injuries must first be performed. Only with shattered kidneys or renal pedicle avulsion injuries, when there is a potential for exsanguination, is exploration required. Unless the UPJ is completely disrupted, urine extravasation from the kidney will usually resolve spontaneously. In order to select nonoperative management, the renal injury needs to be imaged and accurately staged. Conservative management of renal injuries requires strict bed rest until the urine visibly clears, frequent hematocrit blood draws, and reimaging after 2 to 3 days for high-grade renal injuries with noted urine (contrast) extravasation. Persistent bleeding demands repeat imaging, arteriography, or surgical exploration. Worsening or symptomatic urinary leaks require ureteral stenting. Urinomas that are symptomatic of >4 cm usually require percutaneous drainage. Most penetrating kidney traumas demand exploration because the injuries are usually high grade and are associated with other major organ damage. Roughly 75% of renal GSWs and 50% of renal SWs demand exploration. Grade 3 and 4 penetrating injuries can be managed by close observation, yet roughly 25% will develop a pseudoaneurysm or delayed bleed and thus require subsequent angioembolization.

FIGURE 3, Algorithm for renal trauma. BP, Blood pressure; CT, computed tomography; F/u, follow-up; Hct, hematocrit; IVP, intravenous pyelogram; SBP, systolic blood pressure; UA, urinalysis; UPJ, ureteropelvic junction.

Surgery

Absolute indications for exploration are persistent and potentially life-threatening renal bleeding. Such bleeding usually occurs with avulsion of the renal pedicle or a shattered kidney. In the unstable trauma patient, a retroperitoneal hematoma incidentally noted on celiotomy that is pulsatile, expanding, or unconfined strongly suggests an ongoing arterial bleed—and thus demands exploration.

Relative indications for kidney exploration are as follows:

1.
Devitalized renal parenchyma that is greater than 50%.
2.
Urinary extravasation in itself does not demand surgical exploration. The majority (85%–90%) of such cases resolve spontaneously (usually within 72 hours), except for UPJ avulsion injuries. UPJ avulsion injuries will not heal spontaneously, and such injury severity precludes stenting. UPJ avulsions without associated trauma that demands celiotomy are usually damage controlled by a percutaneous nephrostomy tube and surgically repaired later. In stable patients who undergo celiotomy, associated UPJ injuries are typically surgically repaired.
3.
Incomplete staging demands either further imaging or renal exploration.
4.
In patients with two normal kidneys, isolated renal artery thrombosis that is not associated with extensive bleeding or urinary extravasation is best managed conservatively, because revascularization rarely preserves significant renal function. Revascularization should be reserved only for bilateral renal artery occlusion or unilateral occlusion in a solitary kidney, with limited warm ischemia time.
5.
High-grade renal injuries need surgical exploration when abdominal exploration is performed for an associated intra-abdominal injury. Exploring a high-grade blunt kidney injury is controversial and should be attempted only by an experienced urologic surgeon.
6.
High-grade penetrating renal injuries generally should be managed surgically because of high rates of delayed bleeding.

The injured kidney is best exposed through a midline transperitoneal incision. Classic teaching dictates that, for zone 1 hematomas, proximal vascular control takes place before renal exploration. Without control of the hilar vessels, exploration can risk releasing the tamponade effect and thus cause massive bleeding. Uncontrolled bleeding results in a nephrectomy. Consistent proximal vascular control of the renal pedicle for zone 2 hematomas is controversial, as kidney bleeding can typically be controlled by hilar clamping or manual compression. Briefly, repair of the damaged kidney requires broad exposure of the kidney and injured area, temporary vascular occlusion for brisk renal bleeding (hilar Satinsky clamping), sharp excision of all nonviable parenchyma, meticulous hemostasis, watertight closure of the collecting system, and parenchymal defect suture closure with pledgets, over a bolster, and retroperitoneal drain.

Complications

Complications after renal trauma are most commonly prolonged urinary extravasation, delayed bleeding, arterial pseudoaneurysm, abscess, urinary fistula, and hydronephrosis. Renal vascular hypertension after renal trauma is almost always transient. Very rarely, sustained hypertension is seen with subcapsular hematomas that cause parenchymal compression (Page kidney). Delayed renal bleeding from a pseudoaneurysm usually occurs 1–2 weeks after kidney injury. Gross hematuria with clots is the typical presentation.

Ureteral trauma

Incidence and mechanism

External trauma

Ureteral injuries from external trauma are very rare. The mechanism of ureteral injuries is 95% penetrating and 5% blunt. GSWs in proximity to the ureter can cause severe ureteral contusion due to a blast effect. After a deceleration injury, the kidney is often dislocated, and tears typically occur at the fixation point of the UPJ and hilar vasculature. Another mechanism for injury is hyperextension of the back, when the ureter is avulsed, stretched by the lumbar and lower thoracic vertebral bodies. This classically occurs in limber children with a pedestrian versus motor vehicle crash.

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