Mechanisms and types of injury
The ureters are anatomically well-protected by the spine, lumbar muscles (musculus psoas), and pelvic bones. Therefore, significant traumatic force is required to injure them.
- Blunt trauma: is rare. It occurs due to sharp hyperextension, leading to excessive ureteral stretching, or severe compression against the transverse processes of the lumbar vertebrae. The most vulnerable area is the ureteropelvic junction (UPJ). An important risk factor is pre-existing renal pelvis dilation (associated with congenital or acquired obstruction).
- Penetrating wounds (stab, gunshot): are usually focal and injure only a short segment of the wall. Very often they are accompanied by severe injuries to the bowel and major trunk vessels (iliac arteries or veins).
- Blast injury (blast effect): the impact of a shock wave can disrupt the intramural blood supply of the wall, subsequently leading to necrosis of the ureteral tissue.
By severity, they are classified into contusion (contusion), partial tear (partial tear), and complete disruption (complete disruption).
Diagnostic imaging and CT findings
Computed tomography (CT) is the primary tool for detecting injuries. However, using only standard scanning phases can lead to a misdiagnosis.
- Arterial and portal-venous phases: pathological signs may be minimal. The diagnostician may notice only mild fat stranding in the retroperitoneal space or a small fluid collection of low attenuation around the kidney, renal pelvis, or ureter.
- Delayed (excretory) phase: is absolutely essential for making the diagnosis. Late scans clearly visualize extravasation—the escape of high-density contrast-enhanced urine into the periureteral soft tissues.
CT allows for reliable differentiation of the degree of tear. With a partial tear, contrast medium is identified within the ureteral lumen distal to the injury site. With a complete transection, ureteral enhancement below the trauma zone is completely absent, and massive extravasation is visible near the UPJ.
Differential diagnosis: accumulation of contrast-enhanced urine in the right anterior pararenal space can sometimes mimic a duodenal rupture (if the patient was previously given oral contrast).
Management and treatment
Treatment tactics depend directly on the extent of the injury, the mechanism of trauma, and associated complications.
- Conservative management: if there is a small urine leak from the collecting system and antegrade urine flow is unobstructed, up to 87% of cases resolve spontaneously with observation.
- Minimally invasive methods: for persistent leakage and partial tears, placement of a ureteral stent (double-J catheter) is used. Partial UPJ tears are also successfully treated with transurethral stenting.
- Management of urinoma: localized collections of urine (urinomas) can become infected due to bacterial contamination from penetrating wounds or stasis. They require image-guided percutaneous drainage.
- Surgical treatment: complete ureteral transection usually requires placement of a diverting nephrostomy (diverting nephrostomy) prior to definitive surgical reconstruction. Open surgery is also indicated if conservative measures fail, for extensive UPJ tears, or if the urinary tract communicates with low-pressure cavities (pleural or peritoneal).
Iatrogenic injuries: if a ureteral tear or transection is discovered intraoperatively, the defect must be repaired immediately.
Briefly: answers to topical questions
What late complications are typical for ureteral trauma?
Typical complications of unrecognized ureteral trauma include severe infectious and inflammatory processes, lumen strictures, and the formation of abnormal communications with adjacent organs. These include:
- Urinary peritonitis — inflammation of the peritoneum due to urine leakage into the abdominal cavity.
- Phlegmon — diffuse purulent inflammation of adipose tissue.
- Purulent pyelonephritis — severe infectious kidney disease.
- Ureteral stricture — narrowing accompanied by impaired urine passage.
- Ureterogenital fistulas — iatrogenic ureterovaginal and ureterouterine fistulas.
- Vascular fistula — a rare communication between the ureter and the adjacent iliac artery, causing massive hematuria.
Radiologist's rule: "If you see fluid around the kidney on primary CT, make sure to perform a delayed phase." This is the only way to confirm or rule out a urine leak.
Class and exam questions
How to clinically suspect a missed urinary tract injury?
Undiagnosed urine leakage (if the injury was missed on CT) may be indicated by the development of sepsis, unexplained decline in renal function, or persistent elevation of serum creatinine and blood urea nitrogen (BUN).
Why does blunt trauma rarely lead to ureteral rupture?
The ureter lies deep within the retroperitoneal space. It is reliably protected from mechanical impact by the pelvic bone framework, the spine, and the bulk of powerful lumbar muscles.
How to differentiate a partial ureteral tear from a complete one on CT?
In a partial tear, contrast medium continues to enter the ureteral lumen distal to the injury site on delayed scans. In a complete transection, enhancement below the injury zone is absent.
What else to study on this topic
- Main renal artery injuries and the "rim sign" on CT.
- Features and clinical presentation of renal vein thrombosis in trauma.
- Intraperitoneal and extraperitoneal bladder rupture: mechanisms and diagnostics.
- Iatrogenic urinary tract injuries during gynecological surgery.
- Traumatic injury to the renal collecting system and urinoma formation.
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