Renal Trauma

Renal injuries can be some of the most complex and challenging cases a urologist or trauma surgeon may face. The vast majority of renal injuries occur as a result of blunt trauma, and most of these are amenable to nonoperative management. Penetrating renal trauma usually occurs in conjunction with injuries to associated abdominal organs, which require urgent laparotomy. Systematic renal reconstruction at the time of laparotomy provides excellent functional results in the majority of cases.

DIAGNOSIS

Signs, symptoms, and laboratory findings that suggest renal injury should prompt immediate radiologic evaluation in stable patients. Gross hematuria after blunt trauma should warrant renal imaging in all cases. Adults with microhematuria in the presence of shock, deceleration injuries, or signs of significant abdominal, flank, or chest injuries after blunt trauma should also be imaged. Pediatric patients with significant microhematuria or signs of multiple injuries after blunt trauma should be radiographically evaluated. Penetrating wounds of the abdomen or flank with any degree of hematuria also warrant urgent renal imaging.

The best study for assessing the injured kidney in a stable patient is a renal CT scan. Renal images can be obtained in conjunction with an abdominal CT when trauma surgeons need this study to evaluate the extent of associated intra-abdominal injuries. When unstable patients are taken emergently for laparotomy and renal injuries are suspected, a one-shot intraoperative IVP is extremely useful. The intraoperative IVP consists of a high-dose (2 cc/kg) intravenous bolus injection of radiographic contrast; a single film is taken at 10 minutes. No scout film is necessary. This technique provides important information regarding the degree of injury of the kidney in question and the status of the contralateral kidney without delaying resuscitation.

INDICATIONS FOR SURGERY

The decision to surgically repair the traumatized kidney is based on consideration of the patient’s mechanism of injury, hemodynamic stability, associated injuries, and accurate radiographic staging of the injury. The vast majority of blunt traumatic renal injuries are clinically insignificant. At San Francisco General Hospital, fewer than 3% of patients with blunt renal trauma require renal exploration. Penetrating renal injuries, on the other hand, should usually be explored. Approximately 70% of patients with penetrating renal trauma are treated surgically at our trauma center. Only when radiographic staging clearly defines a penetrating injury as minor can a nonoperative approach be used successfully.

Persistent renal bleeding is an absolute indication for renal exploration. Relative indications for renal surgery include extensive urinary extravasation, nonviable renal tissue in association with a parenchymal laceration, incomplete clinical or radiographic staging, and arterial thrombosis. Also, if a trauma surgeon elects to perform an exploratory laparotomy to manage an associated abdominal injury, we will usually repair significant renal injuries at that time in order to prevent late complications. Nearly all renal lacerations occurring from gunshot wounds require immediate repair. In the absence of severe vascular injury or hemodynamic instability, renal reconstruction may safely be attempted. Successful reconstruction can be undertaken despite spillage from bowel injury, pancreatic injury, or other associated injuries.

ALTERNATIVE THERAPY

Nephrectomy, when required after renal trauma, usually occurs when an injury is deemed irreparable or in the setting of hemodynamic instability. Although nephrectomy is clearly a life-saving maneuver in these instances, it is only necessary in about 10% of cases. In general, patients requiring nephrectomy are much more seriously injured, are frequently in shock, and cannot be managed conservatively.

Renal stab wounds are successfully managed nonoperatively in about 50% of cases at San Francisco General Hospital. The types of stab wounds most amenable to an observational approach are those occurring posteriorly or in the flank, where intra-abdominal organs are unlikely to be involved. For those stab-wound patients in whom nonoperative management is being contemplated, renal CT provides excellent information regarding the depth of laceration, extent of urinary extravasation, and size of perirenal hematoma.

SURGICAL TECHNIQUE

Renal exploration in the trauma setting should be carried out through a standard midline abdominal incision. This approach provides complete access to the intra-abdominal viscera and vasculature, and it also gives the greatest flexibility to assess and repair a variety of genitourinary injuries. Major bleeding noted on opening the abdominal cavity should be controlled immediately with laparotomy packs followed by surgical control and repair. Associated injuries to other abdominal organs are usually addressed before examination of the kidneys if the patient is stable. The bowel, liver, spleen, pancreas, and other organs should be inspected systematically and carefully.

The renal vasculature is routinely isolated before a retroperitoneal hematoma surrounding an injured kidney is entered. This creates a safety net for reconstruction and reduces the risk of uncontrolled renal bleeding and subsequent nephrectomy. To facilitate access to the retroperitoneum, the transverse colon is lifted out of the abdomen superiorly and placed on moist laparotomy packs. The small bowel is placed in a bowel bag and lifted anteriorly to the right. An incision is made in the retroperitoneum over the aorta from the level of the inferior mesenteric artery to the ligament of Treitz, which can be divided for additional exposure. If hemorrhage obscures the aorta, the inferior mesenteric vein is identified, and the retroperitoneal incision is placed just medial to this important landmark.

Once the aorta is identified in the lower part of the incision, it is followed superiorly to the left renal vein, which reliably crosses anteriorly. The renal arteries can be found just posterior to the left renal vein on either side of the aorta. If the right renal vein is difficult to isolate through this approach, an alternative method of exposure is to mobilize the second portion of the duodenum off the vena cava. With lateral retraction on the vena cava, the right renal artery can then be isolated in its interaortocaval location.

The ipsilateral renal artery and vein are individually isolated with vessel loops. These vessels are not occluded initially unless bleeding is heavy, which occurs in approximately 12% of cases in our experience.1 Because the vessels are not routinely clamped, renal perfusion is continuous, and warm ischemia is avoided. Patients most likely to require temporary vascular occlusion are those in shock from active, uncontrolled renal bleeding. Vascular occlusion, when necessary for reconstruction, does not increase the incidence of postoperative complications when the warm ischemia time is kept around 30 minutes.

After vascular control, the kidney is exposed by incising the retroperitoneum just lateral to the colon. The colon is reflected medially, and dissection through the hematoma allows renal exposure. After the kidney has been bluntly and sharply mobilized, the entire renal surface, renal vasculature, and upper ureter are routinely inspected for the presence of exit wounds or multiple injured areas. If heavy bleeding ensues, Rummel tourniquets can be applied to the vessel loops for vascular occlusion. First, the renal artery alone is occluded. If bleeding persists, the renal vein is then occluded to eliminate back bleeding.

For major polar injuries, partial nephrectomy offers the best management. Nonviable tissue is sharply debrided from the injured area. Manual compression of the adjoining normal renal parenchyma, rather than formal vascular occlusion, is extremely useful during partial nephrectomy as an adjunct during control of moderate renal hemorrhage. Arcuate arteries are individually suture-ligated with 4-0 chromic suture to control hemorrhage. The collecting system is then closed watertight with a running 4-0 Vicryl suture. Methylene blue may be injected into the renal pelvis with simultaneous compression of the ureter to elucidate any leaks in the collecting system, which may then be oversewn.

The renal parenchymal defect should be covered with thrombin-soaked Gelfoam to enhance hemostasis and then covered with renal capsule, if possible. Typically, after partial nephrectomy for polar injuries, the remaining renal capsule is insufficient to allow for primary closure. In this case, an omental pedicle flap can be brought around the colon or through a window in the colon mesentery and attached with interrupted suture to the existing renal capsule for coverage of the defect. Its excellent vascular supply and lymphatic drainage make omentum an excellent tissue choice for coverage of renal injuries, especially in the setting of concomitant bowel or pancreatic injury. A retroperitoneal drain is placed routinely.

Major injuries to the midportion of the kidney are more difficult to repair than polar injuries, but the same surgical principles apply. Nonviable tissue is removed sharply. Sites of bleeding are individually ligated with fine absorbable sutures, and the collecting system is closed watertight. Interrupted 3-0 chromic sutures placed superficially are ideal for renal capsule approximation. Capsular sutures are best placed without incorporating the underlying parenchyma, as that tissue is extremely friable. Thrombin-soaked Gelfoam bolsters in the defect enhance hemostasis, prevent urinary leakage, and stabilize capsular closure. Again, omentum should be used if primary capsular closure cannot be achieved. We frequently place a row of small titanium staples in the renal capsule near the closure to visualize the operative site on subsequent imaging studies. A retroperitoneal Penrose drain is brought out through a separate incision in most cases. Suction-type drains may initiate or prolong urinary leakage.

Renal stab wounds may be repaired using the same methods detailed above. As discussed, many may be amenable to nonoperative management. If laparotomy is performed for associated injuries, renal reconstruction should be done concomitantly. Tissue destruction is frequently much less than that seen with gunshot injuries. Frequently, entrance and exit wounds may be simply oversewn.

Renal vascular injuries are a major cause of renal loss and may coexist with parenchymal lacerations. Main renal artery or complex renal vein injuries frequently lead to total nephrectomy. Venous injuries may occur along the main renal vein or in segmental branches. In either case, the first step is to temporarily occlude the main renal artery. Vascular clamps are then placed proximal and distal to the venous laceration. A running suture of 5-0 vascular silk is then used to close the venous defect. Segmental arterial injuries are best repaired in a similar fashion. Smaller segmental veins can safely be ligated because of the internal collateral circulation of the venous system. Also, the left main renal vein may be ligated proximally because there is extensive collateral flow through the adrenal, lumbar, and gonadal branches.

Gross blood in the urine usually clears within 24 hours, and patients should be observed at bed rest during this time. Ambulation is resumed once the urine is clear. Serial hematocrits should be monitored because delayed bleeding is possible. Renal angiography and selective embolization may be considered in the event of continued hemorrhage. Retroperitoneal drains are normally removed within 48 to 72 hours. If drainage is excessive, an aliquot may be checked for creatinine; a level similar to that of serum suggests peritoneal fluid rather than urine. Blood pressure is checked before discharge. A radionuclide study is usually obtained around the time of discharge to assess function, and a renal imaging study is again obtained at about 3 months.

OUTCOMES

Complications

Small amounts of urinary extravasation are usually not clinically significant as long as they do not become infected. Large urinomas are best treated with percutaneous drainage. Delayed renal hemorrhage is most likely within the first 2 weeks, and this complication is best treated initially with percutaneous embolization and supportive therapy. Hypertension occurs rarely after renal injuries, and it is usually easily controlled by medical therapy alone. Delayed urinary bleeding may be a sign of a vascular fistula to the collecting system: this complication is frequently difficult to reconstruct and may often be best treated with nephrectomy.

Results

Renal reconstruction has achieved adequate preservation of function in 83% of patients at our institution. We have found renal salvage to be safe in the presence of concomitant bowel or pancreatic injuries.

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