Applied Radiology

Prepared by Andrew Gelbman, DO, PhD and Stuart E. Mirvis, MD, of the Department of Diagnostic Imaging and the Shock-Trauma Center, University of Maryland Medical Center, Baltimore, MD.

PROBLEM:

The patient is a 17-year-old female who sustained multiple injuries following a motor vehicle collision. Images from the initial CT scan and a follow-up scan 4 days later are shown (figures 1-4).

DIAGNOSIS:

Partial ureteral laceration secondary to blunt trauma

IMAGING FINDINGS:

The initial CT scan shows a large, low attenuation fluid collection in the mid-abdomen and pelvis (figure 1). Increased attenuation paralleling the course of the right ureter is consistent with active contrast-enhanced urine extravasation from a ureteral injury (figure 2). Contrast is seen in the distal ureter suggesting that the ureteral injury is incomplete. Associated injuries include a laceration of the left lobe of the liver, comminuted fractures of the right pelvis, and a large pelvic hematoma. The follow-up scan obtained 4 days later also demonstrates the comminuted right iliac wing fracture with a sharp bone spicule projecting medially, abutting the course of the right ureter (figure 3). Delayed images show a small pool of contrast leaking from the ureter at that level (figure 4). Contrast is seen within the ureter proximal and distal to this level, implying partial ureteral continuity.

DISCUSSION:

When the ureter is injured, it may become obstructed, causing hydroureter, hydronephrosis, and loss of renal function. Alternatively, extravasation into the retroperitoneum or peritoneal cavity may occur. Ureteral injuries usually result from surgical intervention and, less commonly, are due to penetrating trauma. The late complications of radiation therapy or migrating foreign bodies such as urinary calculi, bullets, or swallowed objects are rare causes of ureteral injury. Iatrogenic surgical trauma accounts for 95% of all ureteral injuries and may complicate up to 1% of all pelvic operations. More than half of these are gynecologic procedures (most commonly hysterectomy and salpingo-oopherectomy), while urinary tract procedures account for 30% of such cases. Less frequently, surgical procedures on the great vessels, colon, and retroperitoneum are associated with ureteral injury.

The ureter is rarely injured by external violence. It is well protected by its location, posterior to the abdominal viscera and anterior to the psoas major muscle, and by its mobility. The most common cause of ureteral injury due to external violence is gunshot wounds accounting for 95%, although a direct hit by a penetrating missle is a rare event. Only 19 isolated injuries of the ureter were reported in United States armed forces in World War I and 24 in World War II. Knife wounds are the next most common etiology. In total, the ureter is injured in 17% of all penetrating trauma cases. Rarely, crush injuries to the pelvis that involve bone can include injury to the ureter. Avulsion of the ureter at the renal pelvis rarely occurs. This injury is usually seen in children who have hyperextensible spinal columns, causing stretching of the ureter and snapping against the 12th rib and lumbar spine transverse processes.

The classification of ureteral injury is based on the mechanism of injury. Those due to external violence include contusion, partial or complete laceration by penetrating missile, crush, and avulsion at the ureteropelvic junction due to hyperextension injury. Surgical injuries include crush, ligation, and transection. If the adventitia of the ureter is stripped, necrosis may occur in 10 to 14 days due to devascularization. Any of the above may lead to fistula formation. Ureteral damage secondary to radiation may not be seen for months to years after the exposure and usually results in obstruction.

Often, ureteric injury is asymptomatic initially. Late recognition may lead to nephrectomy in up to one-third of patients, in contrast, <5% of patients in whom the injury is diagnosed early require nephrectomy. Delayed recognition of ureteral injury also leads to an increased incidence of ureteral fibrosis and stricture due to the intense inflammatory reaction induced by extravasated urine. Signs and symptoms of a missed ureteral injury include fever, flank mass, flank pain, hydronephrosis, and fistula formation.

Ureteral injury can be investigated radiographically if the patient is not going to undergo surgical exploration. An intravenous urogram is recommended in a patient with penetrating injury to the abdomen, pelvis, or retroperitoneum in the area of the urinary tract; fracture of the 11th or 12th rib, lumbar transverse process, or bony pelvis; or with hematuria and significant abdominal or pelvic trauma. High-dose intravenous urography within the first 24 to 36 hours may identify up to 91% of ureteral extravasations. Usually, ruptures at the ureteropelvic junction are identified easily; however, more distal lacerations may be missed if there is a large urinoma that dilutes the extravasating contrast or the distal ureter is not adequately filled. CT can also demonstrate a urinoma and may localize the level of injury when performed using intravenous contrast. Contrast in the ureter distal to a proximal laceration indicates a partial injury. When performing CT scanning for the evaluation of ureteral injury, it is important that the entire renal collecting system be opacified. If the renal pelvis, ureter, and bladder are not opacified on the initial scan, a delayed scan from the kidney to the bladder is indicated.

The type of ureteral injury, the extent and site of anatomic loss of the ureter, the time of recognition after injury, and the presence of associated injury will affect management. Ureteral injury secondary to stabbing or iatrogenic trauma are usually treated with minor debridement and reanastomosis. In contrast, high-velocity gunshot wounds (>2,500 fps) are complicated by the possibility of delayed necrosis of the ureter due to microvascular damage, and, therefore, resection of the contused segment is indicated. In the case of partial laceration in which the portion of ureter in continuity is still viable, placement of an in-dwelling double-J stent and closure of the wound usually gives good results. If the viability of the remaining intact ureter is in question, or if there is complete laceration of the ureter, all devitalized tissue must be excised before repair. Ureteral injury secondary to radiation often results in stricture formation. Surgical repair is difficult as irradiated tissue heals poorly; permanent internal stenting, surgical diversion, and nephrectomy are considered treatment options.

Selected References

1. Guerriero WG. Uretal injury. Radiol Clin North Am 16(2):237-248, 1989.

2. Feliciano DV, Moore EE, Matlox KL: Trauma, 3rd edition, pp 673-678. Stamford, CT, Appleton & Lange, 1996.

3. Brandes SB, Chelsky MJ, Buckman RF, Hanno PM: Ureteral injuries from penetrating trauma. J Trauma 36:766-769, 1994.

4. Campbell EW Jr, Filderman PS, Jacobs JC: Ureteral injury due to blunt and penetrating trauma. Urology 40:216-220, 1992.

5. Gillenwater JY (ed): Adult and Pediatric Urology.3rd ed. pp. 554-562. St. Louis, Mosby-Year Book, 1996.

6. Ghali AM, El Malik EM, Ibrahim AI, et al: Ureteric injuries: Diagnosis, amanagement and outcome. J Trauma 46(1):150-158, 1999.