30 UPPER URINARY TRACT INJURIES
Fernando J. Kim M.D., Siam Oottamasathien M.D.

1. What is the most common type of renal trauma in the United States, blunt or penetrating?

Show answer
Blunt, by far.

2. Do most kidney injuries require surgery?

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No. Fewer than 2% of blunt injuries require surgery, and many penetrating injuries can also be treated nonoperatively.

3. Are pediatric kidneys more susceptible to major injury?

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Yes. Because of children’s weaker abdominal muscles, less-ossified thoracic cage, decreased perirenal fat, and increased renal size in relation to the rest of the body, the risk for renal injury is greater in the pediatric population.

4. When should potential renal trauma be investigated?

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All blunt trauma patients with gross hematuria or with microscopic hematuria and shock (systolic blood pressure < 90 mmHg) should be closely examined. Penetrating injuries with any degree of hematuria should be imaged. For pediatric patients, liberal use of studies is advisable. When children spill < 50 red blood cells (RBCs) per high-powered field (hpf) on microscopic urinalysis, significant renal injury is rare. Furthermore, shock is not a useful guide in children.

5. When does one suspect renal trauma?

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The mechanism of injury, physical examination (e.g., flank ecchymosis, location of penetrating wounds), and associated injuries (e.g., rib fractures) should raise suspicion of renal trauma. Although the degree of hematuria does not correlate with the degree of renal injury, when hematuria is out of proportion to the history of trauma, it suggests preexisting renal abnormality (e.g., hydronephrosis, ectopic kidney, tumor, cystic disease, vascular malformation). Conversely, renal pedicle injuries (grade 4) may bleed little because of arterial interruption.

6. What imaging study is best to evaluate renal trauma?

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Computed tomography (CT) scan of the abdomen and pelvis with and without intravenous (IV) contrast should be performed, but it is pivotal that the perfusion and excretion phases (10 minutes after IV contrast is administered) are obtained during the study.

7. What is a single-shot IVP, and when do you perform it?

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It is an extremely abbreviated form of intravenous pyelogram (IVP) performed in emergent cases when a full evaluation is not permitted. A bolus (2 mL/kg contrast agent) is injected intravenously, and the first film should be obtained at approximately 10 minutes, with additional films at 10-minute intervals as necessary for diagnosis. Intraoperative IVP is recommended when renal damage is first suggested (e.g., retroperitoneal hematoma) during emergency surgery for other injuries.

8. How is renal trauma classified?

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* Grade 1: contusion
* Grade 2: superficial laceration
* Grade 3: deep laceration without collecting system damage
* Grade 4: contained renal pedicle injury or deep laceration and collecting system damage
* Grade 5: shattered kidney or avulsion of renal hilum

Grade 1, 2, and 3 injuries are safe to watch with nonoperative management, whereas grades 4 and 5 typically require operative intervention for repair or removal. Grade 4 injury (pedicle injury) is picked up by ipsilateral urographic nonfunction and nominal bleeding. Grade 5 injury is manifested by urographic nonfunction, parenchymal shattering, and significant gross hematuria.

9. What are the different kinds of renal pedicle trauma?

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The renal pedicle may be interrupted by thrombosis or complete avulsion; both events are characterized by urographic nonvisualization and minimal hematuria. The most common site of arterial interruption is the junction of the proximal and middle thirds of the main renal artery. Although hematuria is often absent, one may see transitory gross hematuria or microhematuria, emphasizing the requirement for urinalysis in all circumstances.

10. How long can a nonperfused kidney tolerate warm ischemia?

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Irreversible renal damage may be seen in kidneys after 30 minutes of warm ischemia, and after 8 hours of ischemia, renal salvage is minimal. Recently, single reports of renovascular trauma with intimal tear treated with endovascular stents have been encouraging.

11. What is the significance of delayed gross hematuria?

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This occurs 3-4 weeks after trauma and may indicate an arteriovenous fistula. Selective embolization is the next step if conservative therapy (bed rest) fails. Rarely, operative intervention, usually for partial nephrectomy, is necessary.

12. How do you deal with unexpected retroperitoneal bleeding noted at operation?

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A pulsatile hematoma suggests a major vascular injury, and exploration should be preceded by vascular control (both proximal and distal) and preparation for rapid blood replacement. Stable hematomas (above the pelvic brim) may be left undisturbed unless studies (preoperative or intraoperative) disclose severe renal damage. When doubt exists, exploration is justified, with the likelihood of losing a kidney.

13. How are patients with posttraumatic urine extravasation managed?

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When urine extravasation is caused by a major laceration into the collecting system and coexists with significant persistent bleeding, surgical correction is advised. Otherwise, urine extravasation commonly resolves promptly. Reimaging at 48-72 hours defines cases requiring drainage, stenting, or operative repair.

14. What is included in conservative management of renal trauma?

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Conservative management includes bed rest until gross hematuria has subsided. Strenuous activity is avoided until microhematuria has subsided (usually within 3 weeks). Patients followed for grade 5 renal trauma should undergo ultrasonography, CT scan of the abdomen and pelvis, or urography at 6 weeks. Hospitalization is not required during these periods.

15. What is the likelihood of subsequent hypertension?

Show answer
Documented posttraumatic hypertension occurs in < 2% of patients and is renin mediated. Onset generally occurs within the first several months of injury. The mechanisms of posttraumatic hypertension are renal artery stenosis or occlusion, renal parenchymal compression (extravasation of blood or urine), and posttrauma arteriovenous fistula.

16. How are most ureters damaged?

Show answer
In the civilian world, excluding iatrogenic injuries, penetrating trauma is responsible for 4% of ureteral injuries, and 1% are caused by blunt trauma.

KEY POINTS: PRINCIPLES OF URETERAL REPAIR

1. Primary tension-free anastomosis is preferred over stent with absorbable suture.
2. For a distal injury in the lower third of the ureter, perform ureteroneocystostomy; suspend the bladder if tension exists.
3. For middle third injuries, perform end-to-side transretroperitoneal ureteroureterostomy.
4. For proximal injury with significant length loss, use nephrostomy tube for drainage.

17. How do you evaluate and identify ureteral injury?

Show answer
The site and mechanism of trauma should prompt the surgeon to suspect ureteral injury. The clinical manifestations are characteristically subtle and often obscured by coexisting injury and complaints. The majority of gunshot wounds and stabbings that injure the ureter also injure bowel, colon, liver, spleen, blood vessels, or pancreas. Hematuria is often microscopic, but it may be absent. Extravasation of contrast may be detected with noninvasive (IVP and CT scan) and invasive (anterograde and retrograde ureteropyelogram) imaging studies. If ureteral injury is suspected during laparotomy, indigo carmine (1 vial IV bolus) should be given to identify the site of leakage (blue coloration).

18. What are the potential consequences of missed ureteral injury?

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Fever, leukocytosis, azotemia, flank pain, ileus, urinoma, or urinary fistula. Presentation is often delayed by several weeks after the injury.

19. What are the principles of ureteral repair?

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Devitalized tissue must be debrided, and the two ends of the ureters should be mobilized, spatulated, and anastomosed (tension free) over a ureteral stent using absorbable suture. Placement of a drain should be performed without rubbing on the fresh anastomosis. Distal injuries permit direct implantation of the ureter into the bladder. Midureteral injuries may be repaired by primary anastomosis. Pediatric patients are more susceptible to proximal complete ureteral disruption. Urgent surgical repair is mandatory. Rarely, when nephrectomy is not an option and ureteral damage prevents standard methods of reconstruction, other elective and more complex surgical reconstructive techniques may be applied. These include kidney autotransplantation, ileal interposition, transureteroureterostomy, Boari flap with nephropexis, and ureterocalicostomy.

20. The distal ureter is injured and ureteral reimplantation with a psoas hitch (tack up the bladder to the psoas muscle) is performed. Postoperatively, the patient complains of anterior thigh numbness. What did you do wrong?

Show answer
The genitofemoral nerve lies on the anterior aspect of the ileopsoas muscle. You caught this nerve when you synched this to the tendon of the psoas muscle.

References
WEB SITES

1. http://www.east.org/tpg/GUmgmt.pdf
2. http://www.acssurgery.com/abstracts/acs/acs0510.htm

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