# Ureteral and Iatrogenic Urinary Tract Injuries

## Introduction

Ureteral injuries, though uncommon, carry significant clinical consequences. The majority of these injuries are iatrogenic, occurring during surgical procedures. Approximately 75-80% of ureteral injuries arise during gynecologic, colorectal, or urologic surgeries. This high risk is due to the ureter's retroperitoneal course and its close anatomical relationship with pelvic vasculature, uterine arteries, and the rectum, making it vulnerable during surgical dissection. Unfortunately, delayed recognition of these injuries is common and is associated with increased morbidity, including the formation of urinomas, sepsis, and even potential loss of renal function.

## Surgical Anatomy of the Ureter

The ureter extends approximately 25 to 30 centimeters from the renal pelvis to the bladder. Its blood supply is segmental and longitudinal, with the upper ureter receiving branches from the renal artery and gonadal artery, the mid-ureter supplied by branches from the aorta, iliac, and gonadal arteries, and the distal ureter vascularized by the superior and inferior vesical arteries. A critical surgical principle is that the blood supply enters medially in the upper ureter and laterally in the lower ureter. Therefore, preserving the periureteral adventitia during surgical mobilization is essential to maintain this longitudinal blood supply and prevent ischemic injury.

There are several points along the ureter that are particularly vulnerable during surgery. The ureteropelvic junction (UPJ) is at risk during pyeloplasty or upper pole partial nephrectomy. At the pelvic brim, where the ureter crosses the iliac vessels, it is susceptible during lymph node dissection or colectomy. The cardinal ligament region, where the ureter passes under the uterine artery approximately 1.5 to 2 centimeters lateral to the cervix—often referred to as "water under the bridge"—is the most common site of gynecologic injury. Finally, the ureterovesical junction (UVJ) is vulnerable during hysterectomy, cystectomy, or low anterior resection.

## Etiology of Ureteral Injury

### Iatrogenic (75-80%)

The most common cause of ureteral injury is iatrogenic, particularly during gynecologic surgery. Hysterectomy—whether abdominal, laparoscopic, or vaginal—accounts for a significant proportion of these injuries, with an incidence ranging from 0.5 to 2%. Injuries typically occur at the UVJ, the cardinal ligament, or the infundibulopelvic ligament. Colorectal surgeries such as low anterior resection and abdominoperineal resection often injure the distal ureter. Urologic procedures, including ureteroscopy (which can cause perforation or avulsion), radical prostatectomy, radical cystectomy, and retroperitoneal lymph node dissection (RPLND), also contribute to ureteral trauma. Vascular surgeries, particularly aortic aneurysm repair, can injure the mid-ureter during aortic cross-clamping or iliac vessel exposure. Laparoscopic and robotic surgeries pose a unique risk of thermal injury from electrocautery, which is insidious because tissue necrosis may be delayed by 3 to 14 days.

### External Trauma (20-25%)

External trauma accounts for 20 to 25% of ureteral injuries. Penetrating trauma, such as gunshot wounds (the most common traumatic cause) and stab wounds, can directly damage the ureter. Blunt trauma is rare but can cause UPJ disruption from deceleration forces, especially in children. These injuries often occur alongside multiorgan trauma, and abdominal exploration for associated injuries may reveal ureteral damage.

### Mechanisms of Injury

The mechanisms of ureteral injury include ligation, where a suture or clip is inadvertently placed around the ureter, which is the most common iatrogenic cause. Transection can be partial or complete division of the ureter. Thermal injury results from electrocautery, laser, or ultrasonic devices and may cause delayed necrosis. Crush injuries occur from clamp application, while devascularization results from excessive stripping of the periureteral adventitia, leading to ischemic necrosis and delayed stricture formation. Avulsion, a severe form of injury, can occur during ureteroscopy when the ureter is intussuscepted by a basket extraction.

<image>Anatomic diagram of the female pelvis showing the three most common sites of iatrogenic ureteral injury: (1) at the infundibulopelvic ligament during ovarian vessel ligation, (2) at the cardinal ligament where the ureter passes under the uterine artery ("water under the bridge"), and (3) at the ureterovesical junction during vaginal cuff closure or bladder dissection, with the ureters traced from kidneys to bladder and vulnerability zones highlighted</image>

## Clinical Presentation

### Intraoperative Recognition (30-40%)

Intraoperative recognition of ureteral injury occurs in 30 to 40% of cases. It may be identified by direct visualization of the injury or the presence of urine in the operative field. Intraoperative cystoscopy with intravenous indigo carmine or fluorescein can be used to assess ureteral patency; absence of efflux from a ureteral orifice indicates obstruction or transection. Early identification during surgery leads to the best outcomes.

### Delayed Presentation (60-70%)

The majority of ureteral injuries present in a delayed fashion, typically 60 to 70% of cases. Patients may develop flank pain, fever, and elevated serum creatinine. Prolonged ileus or abdominal distension can also be signs. Urinoma formation, a fluid collection of urine, may present as a palpable mass or as drainage of clear fluid from a wound. Vaginal or wound urinary leaks manifest as constant fluid discharge, and analysis showing fluid creatinine higher than serum creatinine confirms urine leakage. Sepsis may develop from an infected urinoma or an obstructed, infected kidney. Diagnosis is established by imaging such as CT urogram with delayed images, retrograde pyelogram, or intravenous pyelogram (IVP).

## Management Principles

### General Principles

Management begins with debridement of devitalized tissue, especially in cases of thermal or crush injury. The ureteral ends should be spatulated to prevent stricture formation at the anastomosis. Repairs require a tension-free, watertight, mucosa-to-mucosa anastomosis using absorbable sutures, typically 4-0 or 5-0 Vicryl. The repair is stented with a double-J ureteral stent for 4 to 6 weeks to maintain patency. A retroperitoneal drain should be placed near the anastomosis to monitor for leaks. Preservation of the periureteral blood supply is critical, so excessive mobilization should be avoided.

### Repair Based on Location

#### Upper Ureter Injuries

For upper ureter injuries, primary ureteroureterostomy with an end-to-end spatulated anastomosis is preferred for short defects less than 2 to 3 centimeters. In cases of UPJ injuries or failed pyeloplasty, ureterocalicostomy may be performed, which involves anastomosing the ureter to the lower pole calyx after partial amputation of the lower pole.

#### Mid-Ureter Injuries

Mid-ureter injuries can also be repaired with primary ureteroureterostomy for short defects. For longer defects, transureteroureterostomy (TUU) can be performed, which connects the injured ureter to the contralateral ureter. However, TUU is contraindicated in patients with stone disease, transitional cell carcinoma, retroperitoneal fibrosis, or prior radiation. For extensive injuries or failed repairs, ileal ureter interposition using a segment of ileum to bridge defects longer than 10 centimeters is an option.

#### Distal Ureter Injuries (Most Common)

Distal ureter injuries are the most common and are best managed with ureteroneocystostomy, or ureteral reimplantation, which is considered the gold standard. If sufficient ureteral length exists, a direct reimplantation to the bladder can be performed without tension. When the gap is larger, a psoas hitch procedure mobilizes and fixes the bladder to the ipsilateral psoas tendon with non-absorbable sutures, adding 3 to 5 centimeters of reach. For even longer defects ranging from 5 to 10 centimeters, a Boari flap—a tubularized bladder flap—is used to bridge the defect, ensuring a base-to-length ratio of at least 3:1 to maintain adequate blood supply. When feasible, a non-refluxing reimplantation is preferred, employing submucosal tunnel techniques such as Lich-Gregoir or Politano-Leadbetter.

### Endoscopic Management

Endoscopic management is appropriate for partial ureteral injuries with minimal extravasation and involves ureteral stenting, which can be placed retrograde or antegrade. Percutaneous nephrostomy provides emergent drainage of an obstructed, infected kidney and serves as a temporizing measure while planning definitive repair. Balloon dilation or endoureterotomy may be used for short ureteral strictures resulting from prior injury.

<image>Surgical illustrations showing distal ureteral repair techniques: (1) direct ureteroneocystostomy with submucosal tunnel, (2) psoas hitch procedure with bladder fixed to psoas tendon and ureter reimplanted into the mobilized bladder, and (3) Boari flap with a tubularized bladder flap bridging a longer ureteral defect with the ureter anastomosed to the flap tip, each with ureteral stent depicted in place</image>

## Prevention of Iatrogenic Injury

Prevention strategies include preoperative ureteral stenting, which can be either illuminated or standard stents, to facilitate intraoperative identification of the ureters. This is particularly useful in complex pelvic surgeries, reoperative cases, or when operating within a radiation field. Intraoperative cystoscopy with intravenous indigo carmine or fluorescein is recommended after hysterectomy to confirm bilateral ureteral efflux, as endorsed by the American College of Obstetricians and Gynecologists (ACOG). Meticulous surgical technique is paramount, emphasizing the identification of the ureter before ligating any pedicle—summarized by the phrase "see it before you clip it." Surgeons must also be aware of anatomic variants such as duplex ureters, retrocaval ureters, and ectopic ureters. Minimizing the use of thermal energy near the ureter by using cold scissors for dissection when in close proximity further reduces the risk of injury.

## Special Situations

### Radiation-Induced Ureteral Stricture

Radiation-induced ureteral strictures typically present months to years after radiation therapy. The underlying pathology involves ischemic injury to the ureteral wall, leading to progressive fibrosis. Endoscopic management often fails in these cases, and surgical repair with well-vascularized tissue, such as an omental wrap or a Boari flap reinforced with omentum, is preferred. In refractory cases, autotransplantation or nephrectomy may be necessary.

### Ureteral Avulsion During Ureteroscopy

Ureteral avulsion is the most feared complication during ureteroscopy and usually occurs during stone basket extraction or when a large ureteroscope is forced through a tight ureter. Immediate recognition is essential, and efforts should be made to place a guidewire and nephrostomy tube to maintain drainage. Surgical repair options include ureteroureterostomy or reimplantation, depending on the location and length of the avulsed segment. Prevention involves avoiding forceful passage, using a ureteral access sheath, and never pulling a basket against resistance.

<image>Algorithm for management of ureteral injuries based on timing of recognition (intraoperative vs. delayed), location (upper, mid, distal), and defect length, showing decision pathways leading to primary repair, ureteroureterostomy, psoas hitch, Boari flap, transureteroureterostomy, ileal ureter, or nephrectomy with key principles annotated at each decision node</image>

## Clinical Pearls

Most ureteral injuries are iatrogenic, with the ureter passing under the uterine artery—often described as "water under the bridge"—making it particularly vulnerable during hysterectomy. Intraoperative cystoscopy confirming bilateral ureteral efflux should be performed after every hysterectomy to detect injuries early. Thermal injuries are especially insidious because tissue necrosis may not become apparent until 3 to 14 days postoperatively; therefore, any unexplained flank pain, fever, or fluid drainage after surgery should raise suspicion for delayed ureteral injury. For distal ureteral injuries, ureteroneocystostomy with a psoas hitch is the most commonly used and reliable repair technique. Preservation of the periureteral adventitia during mobilization is crucial because it contains the longitudinal blood supply essential for healing. When uncertainty exists regarding the extent of injury, stenting and drainage are prudent; placing a percutaneous nephrostomy and ureteral stent allows for temporizing management and facilitates definitive repair under optimal, planned conditions.

## References

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