Ureteroarterial fistulas (UAFs) are rare, life-threatening conditions characterized by an abnormal connection between the ureter and arterial system, often resulting from chronic inflammation or previous medical interventions. While these fistulas have been known for over a century, their occurrence has increased in recent decades due to advances in oncological surgeries and radiotherapy, particularly in the pelvic region. Early clinical suspicion is essential, as the primary symptom of UAFs, hematuria, can rapidly lead to critical complications if not addressed swiftly.
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Epidemiology and Risk Factors
The increasing prevalence of UAFs is largely attributable to the growing number of patients undergoing abdominopelvic surgeries and receiving chronic ureteral stents. The majority of these cases are linked to:
- Oncological surgeries, particularly in gynecological and colorectal cancers.
- Pelvic radiotherapy, which can lead to tissue fibrosis and weaken both the ureteral and arterial walls.
- Chronic ureteral stenting, especially in patients with recurrent urinary tract obstructions or post-surgical complications.
Less commonly, UAFs can occur due to intrinsic vascular abnormalities like pseudoaneurysms, which are structural weaknesses in the arterial walls that predispose them to rupture. The primary clinical manifestation of UAFs is intermittent hematuria, which can escalate from mild to life-threatening if the fistula ruptures. Patients may also present with symptoms of urinary retention, infection, or flank pain, particularly in advanced cases.
Mechanisms and Pathophysiology
The development of a ureteroarterial fistula is often the result of a chronic inflammatory process that erodes both the arterial and ureteral walls at their point of contact. The weakened arterial wall, usually involving the common iliac artery, pulsates against a fibrotic ureter, gradually forming the fistula. In many cases, radiation therapy causes microvascular damage that further weakens the arterial walls, while surgical interventions can lead to the ureter being fixed or displaced, adding to the mechanical stress.
The chronic presence of a ureteral stent, which is often required in patients with hydronephrosis or recurrent infections, further exacerbates the local tissue damage. Over time, the persistent pressure from the arterial pulse and the presence of scar tissue increase the likelihood of a fistula forming.
Clinical Presentation
The hallmark of UAFs is hematuria, occurring in nearly all cases. The bleeding may be mild and intermittent at first but can rapidly escalate to massive hematuria, causing hemodynamic instability. In 13% of cases, severe hemorrhage is triggered during ureteral stent replacements, which can aggravate the fragile arterial-ureteral connection. In some cases, the hematuria may not immediately point to UAFs, as other symptoms like flank pain or urinary tract infection might overshadow the bleeding. Hence, maintaining a high level of suspicion is crucial, especially in patients with a history of abdominopelvic surgery or chronic stenting.
Diagnostic Challenges
Diagnosing UAFs can be particularly challenging due to their rarity and the nonspecific nature of the symptoms. The diagnostic gold standard remains pelvic arteriography, but its sensitivity ranges from 50% to 70%, depending on factors like the presence of blood clots or local tissue compression. When arteriography fails to reveal the fistula, provocation maneuvers—such as manipulating the ureteral stent—can help by increasing arterial pressure and revealing the site of extravasation.
Cystoscopy can be used to visualize blood clots within the bladder or ureteral orifice, indicating the location of the bleeding. Additional diagnostic tools like retrograde pyelography or computed tomography (CT) angiography may assist, but their sensitivity is generally lower, ranging from 30% to 50%. In cases where non-invasive techniques are inconclusive, exploratory surgery may be necessary to locate the fistula and control the bleeding.
Therapeutic Approaches
The treatment of UAFs has evolved significantly over time. Historically, open surgical repair was the mainstay of treatment, often involving arterial ligation, bypass grafting, or arterial embolization. However, the introduction of endovascular stenting has revolutionized UAF management. Today, covered stents are the gold standard for managing these fistulas, offering a minimally invasive solution with fewer complications and faster recovery times compared to open surgery.
Studies have shown that endovascular stents provide excellent short-term results, with a high success rate in controlling hematuria and restoring hemodynamic stability. Nevertheless, complications such as lower limb ischemia, stent infection, and stent thrombosis remain concerns, particularly in the long term. In some cases, arterial embolization using coils is employed, especially when the fistula involves the internal iliac artery.
Surgical intervention remains necessary in cases of complex fistulas, where infection is suspected, or when endovascular treatment fails. In such scenarios, open surgery allows for direct repair of the fistula, often accompanied by nephroureterectomy (removal of the kidney and ureter) in cases of severe infection or obstruction.
Case Studies
Two illustrative cases highlight the complexity and variability of UAF presentations:
- Case 1: A 45-year-old woman with a history of gynecological cancer and multiple ureteral stent placements developed severe hematuria, which was diagnosed as a UAF through angiography. A covered stent was successfully placed, resolving the hematuria without the need for open surgery.
- Case 2: A 79-year-old woman with recurrent hematuria following ureteral stenting presented with shock. Arteriography failed to reveal the fistula initially, leading to a nephroureterectomy and arterial repair. This case underscores the need for prompt diagnosis and intervention, as delayed treatment significantly worsened her prognosis.
Prognosis and Long-Term Management
Although endovascular techniques have significantly reduced the morbidity associated with UAFs, the condition remains life-threatening. Post-treatment complications, such as stent infection or recurrence of bleeding, necessitate long-term monitoring. The use of antibiotic prophylaxis is recommended, especially for patients with a history of infection or when stent placement is performed in a contaminated field. Regular follow-ups, including imaging studies and clinical assessments, are essential to monitor for late-onset complications like stent thrombosis or the development of pseudoaneurysms.
Conclusion
The management of ureteroarterial fistulas continues to evolve with the advent of endovascular treatments, which offer a less invasive and more effective solution compared to traditional open surgery. However, due to the high morbidity and mortality rates associated with UAFs, early diagnosis and prompt intervention are critical for improving patient outcomes. A multidisciplinary approach involving urologists, vascular surgeons, and interventional radiologists is essential for optimizing both diagnostic accuracy and therapeutic success. Long-term follow-up is vital to detect and address complications early, ensuring sustained patient health and safety.