Management of a Renal Artery Aneurysm with Coil Embolization

ABSTRACT: We describe a case of a 51-year-old female who was incidentally noted to have a renal artery aneurysm on computed tomography (CT). The aneurysm was not seen on an abdominal CT performed 4 years prior, so the patient underwent successful percutaneous coil embolization. The indications for repair of such aneurysms are unknown, and there are a myriad of surgical and percutaneous management options. Because of the increase in abdominal imaging, the incidence of renal artery aneurysms is likely to rise. We describe the case and review the literature surrounding the epidemiology, outcome and management of renal artery aneurysms.


J INVASIVE CARDIOL 2008;20:470–472

Key Words: renal artery embolization; transcatheter coil embolization

Renal artery aneurysms, which are most frequently asymptomatic, are rare, with a reported incidence of between 0.01% in autopsy studies1 and 0.7–1.0% in large-scale screening studies with various imaging modalities.2,3 Currently, because of more widespread abdominal imaging, however, the incidence of clinically recognized renal artery aneurysms may be on the rise. The etiology of most renal artery aneurysms is unknown, although commonly cited risk factors include female gender (about a 2:1 ratio in large series), atherosclerosis, fibromuscular dysplasia, connective tissue disorders and congenital collagen vascular disorders such as Ehlers-Danlos syndrome or Marfan’s syndrome.4–6 The proper management of renal artery aneurysms is unknown. Options include watchful waiting or intervention (including various surgical and endovascular techniques). Some authors suggest repair of aneurysms in all women of childbearing age regardless of size, > 1.0 cm among patients with hypertension, watchful waiting of aneurysms 1.0–1.5 cm among normotensive patients and repair of all aneurysms > 1.5 cm or > 2.0 cm regardless of the presence or absence of hypertension.4,5,7 Regardless of the indication, repair has been associated with a decrease in systemic blood pressure and a reduction in the number of antihypertensive medications required to maintain a normal blood pressure in certain cases. Here we present the case of a 51-year-old female with multiple medical problems, including hypertension, who was incidentally noted to have a 1.7 x 1.5 cm left renal artery aneurysm on computed tomography of the abdomen. She was treated with endovascular coil embolization. We review the literature on renal artery aneurysms and their management.

Case Report. A 51-year-old Caucasian female with a history of hypertension, hyperlipidemia, ulcerative colitis with surgical ileoanal pouch formation and eosinophilic lung disease was incidentally noted to have a renal artery aneurysm on computed tomography (CT) obtained to evaluate a renal cyst seen on a prior renal ultrasound. Subsequent CT angriography further defined a 1.5 x 1.7 cm left renal artery aneurysm arising from the superior segment of the renal artery (Figure 1A). The aneurysm was a new finding and was not previously noted on serial abdominal CT scans obtained to monitor stable, ill-defined hepatic lesions, with her last abdominal CT performed about 4 years prior. The patient denied any complaints of abdominal or back pain or changes in urinary habits. No variation was noted in the patient’s renal function.

Angiography was performed to better define the anatomy of the aneurysm, which revealed that it arose from a trifurcation. Unfractionated heparin was administered intravenously. A 6 Fr Ansel guiding sheath (Cook, Inc., Bloomington, Indiana) was utilized to engage the left renal artery, providing adequate support. A Transit catheter (Cordis Corp., Miami Lakes, Florida) was delivered into the aneurysm. Three 0.018 x 8 x 14 Nestor coils (Cook U.K. Ltd., Letchworth, United Kingdom) were then delivered into the aneurysm (Figure 1B). The superior branch of the left renal artery was left unaffected by the coils, and digital subtraction revealed normal flow of contrast into the kidney with decreased flow noted in the aneurysm (Figure 1C). The patient tolerated the procedure well.
Repeat CT of the abdomen performed about 2 months afterward revealed no renal perfusion defects and an opacified renal artery aneurysm that had not grown in size.

Discussion. Renal artery aneurysms are rare, with the incidence ranging from 0.01–1.0%, depending on the population and screening modality.1–3 They are usually asymptomatic, although complications include arteriovenous fistula formation and, rarely, catastrophic rupture leading to nephrectomy8 or death.5 However, because of its place in the retroperitoneum and the possibility of tamponade in this anatomic location, rupture of a renal artery aneurysm may not be as life-threatening as rupture of other visceral aneurysms such as aortic or splenic (the two more prevalent aneurysms found in the abdomen).

Signs or symptoms ascribed to renal artery aneurysms include hypertension (73–89%), pain (18%) and hematuria (9%), although the majority of cases (55%) are discovered incidentally on abdominal imaging.4,5,9 In two large series, there was an approximately 2:1 ratio of women to men, which may be due to differences in the prevalence of abdominal imaging performed in women, differences in the prevalence of fibromuscular dysplasia or vascular changes during or after pregnancy.4,5 Other risk factors include connective tissue disorders such as Takayasu’s arteritis and congenital collagen vascular disorders such as Ehlers-Danlos syndrome and Marfan’s syndrome. There does not appear to be a significant difference in the incidence of left versus right renal artery aneurysms, and the most common location in a series of 252 renal artery aneurysms was at the main renal artery bifurcation (60%).5

The indications for intervention are unknown, although authors have suggested renal artery aneurysms in women of childbearing age, evidence of aneurysmal enlargement on repeat imaging, aneurysms > 1.5 cm or > 2.0 cm in diameter in all patients and aneurysms 1.0–1.5 cm in diameter among patients with hypertension.4,5,7

There is a wide range of interventional options, depending largely on the size of the aneurysm, its anatomical location and the presentation. Surgical options include open repair with aneurysmectomy and angioplastic closure or reimplantation of a segmental renal artery, aneurysmectomy and renal artery reconstruction with a bypass graft and ex vivo repair and autotransplantation and nephrectomy.4,5,10,11 In two large series comprising 230 patients with 324 renal artery aneurysms, there was 1 perioperative death (0.4%) (a 66-year-old male with advanced cirrhosis and a symptomatic renal artery aneurysm). There were 13 perioperative complications (5.6%), including 2 wound infections and 1 each of postoperative hemorrhage requiring reoperation, deep vein thrombosis, pneumonia requiring intubation, third-degree heart block, pancreatitis, perforated peptic ulcer, ileus, acute renal failure, chylous ascites, a sacral decubitus ulcer and a loss of pregnancy in a gravid woman.

Endovascular techniques include coil embolization,12,13 covered stent implantation14 or a combination of coil embolization and noncovered stent implantation.15 The choice of intervention is largely dependent on the anatomy of the aneurysm, and because there have not been any large series of percutaneous interventions, the optimal choice is unknown.

Reduction in blood pressure and a decreased need for antihypertensive medications has been well documented following interventions for renal artery aneurysms. In the two largest series of patients undergoing surgical repair, there was a significant decrease in blood pressure and the number of antihypertensive medications among the 40 patients with accurate pre- and postoperative blood pressure measurements.4,5 Although a reduction in blood pressure following percutaneous intervention has been reported, whether the same systematic benefit noted with surgical repair exists following percutaneous intervention is unknown. The mechanism behind this reduction in blood pressure and need for antihypertensives is unknown. One could speculate that more turbulent flow in the renal artery would lead to a decreased effective renal blood flow (RBF), a lower glomerular filtration rate (GFR) and, therefore, activation of the renin-angiotensin-aldosterone (RAA) axis. Exclusion of the aneurysm from the circulation may thus improve effective RBF, GFR and, possibly, downregulate the RAA axis.

Conclusion. Renal artery aneurysms are rare. Therefore, neither the indication for intervention nor the proper technique, surgical or endovascular, is known. No matter the type of intervention, successful repair or exclusion of renal artery aneurysms has been associated with a potential decrease in blood pressure. Endovascular techniques are an attractive first option for treatment of noted renal artery aneurysms.