Blunt rapid deceleration injuries are the most common etiology for renal trauma. Although blunt renal injuries tend to be minor in nature, some may be associated with damage to the renal vessels, renal artery thrombosis, or renal pedicle avulsion. Major renal injuries are often associated with multiple associated nonurologic injuries in the setting of rapid deceleration or penetrating trauma.

Hematuria is the best indicator of urinary system injury, although the degree of hematuria and the severity of the renal injury may not correlate. Microscopic hematuria seems to herald the presence of renal injury more commonly when shock is present,¹,²,³ and less so when it is not. Microscopy is not necessarily required to evaluate hematuria, as the dipstick method is rapid and has a sensitivity and specificity for detection of microhematuria of more than 97%.⁴

The indications for radiographic evaluation after blunt trauma are gross hematuria, microscopic hematuria with shock, and major deceleration injury in the presence of significant nonurologic-associated injuries.³,⁵,⁶ Blunt trauma patients with isolated microhematuria do not in general require immediate imaging. Penetrating injuries with any degree of hematuria should be imaged.

Pediatric patients sustaining blunt abdominal trauma are at greater risk for renal injury than adults because children have less perirenal fat to protect and stabilize the kidney.¹ Shock may be a less useful criterion in children to determine if imaging studies should be performed.⁷ Children with insignificant microhematuria (<50 red blood cell [RBC] per high power field [HPF]) after blunt trauma are a low-yield group and usually do not require urgent renal imaging.⁷

The kidney has remarkable healing properties, and nonoperative management has therefore become the treatment of choice for the vast majority of non-life-threatening renal injuries. Nonoperative management results in an excellent long-term outcome in most cases. All grade 1 and 2, and most grade 3 renal injuries can be managed nonoperatively. Exploration of grade 4 and 5 renal injuries often results in nephrectomy; recent data indicates that many of these patients can be managed safely with an expectant approach.¹³,¹⁴

Patients with suspected penetrating renal injury who are otherwise stable should undergo radiographic staging, whenever possible, to define the injury. Renal gunshot injuries require exploration only if they involve the hilum or are accompanied by signs of continued bleeding, ureteral injuries, or renal pelvis lacerations.¹⁵ Stab wounds and low-velocity gunshot wounds may often be managed conservatively with an acceptably good outcome.¹⁶ Tissue damage from high-velocity gunshot injuries may be more extensive.

The site of penetration by stab wound has an important influence on management—if posterior to the anterior axillary line, most (88%)¹⁷ may be managed nonoperatively.¹⁸,¹⁹ A systematic approach based on clinical, laboratory, and radiologic evaluation may minimize negative exploration after renal stabbing, without increasing morbidity from missed injury. Expectant management of renal stab wounds can be attempted on the hemodynamically stable patient, especially if ureteral and renal pelvis injuries can be ruled out. Ultimately, 98% of blunt renal injuries can be managed nonoperatively.

Grade IV and V injuries more often require surgical exploration, but even many of these can be managed without renal surgery if carefully staged and selected. Patients with high-grade injuries selected for nonoperative management should be closely monitored for persistent bleeding with repeat vital signs and serial hematocrits. If significant urinary extravasation persists beyond 48 hours, prompt urologic consultation with retrograde placement of an internal ureteral “double J” stent (and a urethral catheter to prevent urinary reflux) will often prevent prolonged urinary extravasation and improve perirenal urinoma formation, sepsis, and ileus.²⁰ Follow-up abdominal CT scans are reserved for high-grade injuries and symptomatic patients only (dropping hematocrit, flank pain, fever, etc.). Should renal bleeding persist, or delayed bleeding occur, angiographic studies with embolization of bleeding vessels will often obviate surgical intervention. It is popularly believed that attempts to repair a bleeding kidney in the days after injury when inflammation is maximal (say 3 to 30 days) will inevitably result in nephrectomy, so it seems prudent to attempt expedient angioembolization if possible.

The only absolute indication for renal exploration is life-threatening hemodynamic instability due to renal hemorrhage, irrespective of the mode of injury.²⁴ Another strong indication for renal exploration is an expanding or pulsatile perirenal hematoma identified at exploratory laparotomy (this finding heralds a grade 5 vascular injury and is quite rare). Relative indications for surgery include suspected renal pelvis injury or persistent bleeding (≥3 units per 24 hours). It has been recognized that most injuries that have urinary extravasation and devitalized kidney fragments heal with nonoperative treatment.²⁵

Renal reconstruction (renorrhaphy) by debriding, oversewing, and covering the defect is feasible in most cases (see Table 2), but partial nephrectomy may be required when large amounts of tissue are damaged, especially at the pole of the kidney. Obtaining early vascular control before opening the Gerota fascia can decrease renal loss caused by bleeding during attempted renal repair (see Fig. 1).²⁶ In a series of 133 renal units in which early vessel isolation and control before opening the Gerota fascia was achieved, McAninch et al.²⁴ reported a very high renal salvage rate of 89%. Early vascular control does not increase postoperative azotemia or mortality.

Renovascular injuries are associated with extensive associated trauma and increased perioperative and postoperative mortality and morbidity. Prompt nephrectomy is usually the treatment of choice except in those very rare cases in which there is a solitary kidney or the patient has sustained bilateral vessel injuries (see Fig. 2).¹⁷ Attempts at surgical repair of renal artery thrombosis largely fail, and certainly after 8 hours the kidney cannot be salvaged. Many patients with renal vascular injury are critically injured, with numerous associated organ injuries, low body temperature, and poor coagulation; the advisability of major vascular repair over a nephrectomy is limited in the unstable patient if a normal contralateral kidney is present. Damage control with placement of packs and planned return for corrective surgery within 24 hours is another reasonable alternative option.²⁷ Because the kidney is a paired organ it is sometimes sacrificed with alacrity in patients who would not truly be in danger from an attempted repair. In a recent series of 1,360 adult patients with renal lacerations 23% underwent surgery, and an appalling 64% of these got a nephrectomy.²⁸ This harmful practice must be avoided.

Early complications of renal injury include bleeding, infection, perinephric abscess, sepsis, urinary fistula, hypertension, urinary extravasation, and urinoma. Delayed complications include bleeding, hydronephrosis, calculus formation, chronic pyelonephritis, hypertension, arteriovenous fistula, and pseudoaneurysm, although these are all less common. Urinary extravasation can usually be managed expectantly as most resolve spontaneously. In cases where there is persistent leakage with fever and/or sepsis, ureteral stent placement or percutaneous drainage is usually feasible and curative.

Unlike renal injuries, nearly all ureteral injuries occur as a result of penetrating or iatrogenic trauma. And unlike renal
injuries, the presence of hematuria is not a reliable indicator of ureteral injury. Many (25% to 45%) cases of ureteral injury will not have even microscopic hematuria,²⁹,³⁰ so a high index of suspicion is required.

The rare entity of ureteropelvic junction (UPJ) disruption consequent to rapid deceleration injury is associated with an unusual pattern of either medial or “circumrenal” contrast extravasation seen on CT.³¹ Children are felt to be more susceptible because of their hyperextensible vertebral column.³²

Wound location is felt to be the best indicator of ureteral injury, and direct exploration is the best means of detecting its presence. Intraoperative detection requires a high degree of suspicion. The trajectory of the knife/missile must be carefully examined and ureteral exploration undertaken in all cases of potential injury. Intravenous infusion or direct ureteral injection of indigo carmine will often produce a pool of colored urine, which may guide intraoperative detection of ureteral injury.

Liberal use of preoperative diagnostic tools such as CT is helpful, whenever possible. Vigilance for delayed presentation of ureteral injuries will also allow detection of injuries missed on presentation. Fever, leukocytosis, and local peritoneal irritation are the most common signs of missed ureteral injury and should always prompt CT examination.

Repair of the ureter must be meticulous, and urologic consultation should be promptly sought to prevent adverse
medicolegal consequences. Ureteral blood supply is tenuous and the sequelae of imperfect repair include urine leakage, abscess, fistula, and refractory ureteral stricture, requiring additional surgical procedures and/or nephrectomy.

Primary repair is recommended in most ureteral injuries. Principles of primary ureteroureterostomy involve limited debridement followed by creation of a spatulated, watertight closure using optical magnification, with interrupted or running 5-0 or 6-0 absorbable monofilament such as Maxon (polyglyconate).²⁹ An internal stent and retroperitoneal drain are placed in most cases. This technique is used primarily for injuries of the upper two thirds of the ureter.