Discussion

Renal artery aneurysms including pseudoaneurysms (RAAs) are localized dilations of the renal artery and/or branches. Although rare, there has been a recent increase in the discovery of renal arteriovenous fistulas secondary to trauma, inflammation, renal surgery, and percutaneous needle biopsy [4]. However, more recent literature has demonstrated that the overall incidence ranges between 0.01% and 1% [4,5]. This increases to 2.5% when only patients with hypertension are considered [5] and can be as high as 39% in patients with hypertension unresponsive to medical therapy [6,7]. The mean age at diagnosis is 60 years. RAAs occur more commonly in men and are primarily located on the right [8]. RAAs can be either congenital or acquired. Congenital RAAs have been associated with autosomal dominant polycystic disease, fibromuscular dysplasia, and tuberous sclerosis [9]. Acquired etiologies include long-standing untreated hypertension, atherosclerosis, blunt [4,10] and penetrating trauma, recent surgical manipulation (open, laparoscopic, and/or endovascular) [11], infectious angiomyolipomas (i.e., mycotic) [12], polyarteritis nodosa [8], malignancy, coagulopathy, radiation, and/or cyclophosphamide use [8]. The risk of rupture is thought to vary inversely with size, and most investigators agree that an aneurysm exceeding 2 cm is more likely to undergo rupture. Most RAAs are discovered on a work-up for hypertension (55%) and are more frequently being discovered incidentally during unrelated abdominal imaging (i.e., radiography, color Doppler ultrasound, CT, and magnetic resonance [MR] imaging or angiography) [4]. Although angiography is the gold standard, perhaps the best noninvasive test to evaluate location, size, structure, and relation to nearby organs is CT/MR angiography [8]. When patients present with symptoms, they are usually flank pain and hematuria that can range from mild microscopic hematuria to gross hemorrhage leading to hemodynamic instability [13].

Indications for treatment include hemorrhage, uncontrolled hypertension, pain, progressive enlargement, presence of an arteriovenous fistula, with size >2 to 2.5 cm or size >1 cm in a female of childbearing age [14]. Currently, endovascular surgery is the intervention of choice in elective or emergent circumstances. Accepted endovascular treatments include embolization (i.e., gelfoam, coils, alcohol) or stenting across the aneurysm [15]. There have also been case reports of successful management of RAAs with percutaneous thrombin injection directly into the aneurysm. Factors that may preclude endovascular management are size and multiplicity, although there have been reports of successful endovascular management of large (10 cm) RAAs endovascularly [15], like our case and another case in Korea [16].