Author Affiliations: From the Department of Surgery, Bronx Lebanon Hospital Center, Bronx, New York. Correspondence: Bala Gangadhara Thatigotla, MD, Department of General Surgery, Apt 4A, 1650 Sellwyn Avenue, Bronx Lebanon Hospital Center, Bronx, NY 10457. Email: firstname.lastname@example.org. Manuscript submitted July 30, 2008, provisional acceptance given September 3, 2008, accepted October 10, 2008. Disclosure: The authors report no financial relationships or conflicts of interest regarding the content therein. ____________________________ Abstract Previously elusive vascular anomalies such as renal artery aneurysms and renal arteriovenous fistulas (RAVF) are now more commonly diagnosed by routine use of abdominal imaging, mostly computed tomography scans and magnetic resonance imaging scans. Arteriovenous malformations can be congenital or acquired. RAVF may be asymptomatic or present as hypertensive cardiopathy, congestive heart failure, or severe renal hematuria. We present the case of a patient with a congenital RAVF as well as high-output congestive cardiac failure. The RAVF was managed by nephrectomy and ligation of the fistula. We discuss the diagnostic and therapeutic features of this case and review the literature. Introduction The exact mechanism of the formation of congenital renal arteriovenous fistulas (RAVF) is not clear. However, these fistulas are thought to be the result of an extraparenchymal renal arterial aneurysm that erodes into adjacent veins. Although RAVF are uncommon even with large renal aneurysm, they are usually associated with such aneurysms. Fibromuscular dysplasia of the renal arteries is a leading cause of renovascular hypertension, but when fibrodysplasia of the medial layer of an artery is associated with a renal artery aneurysm and a high-outflow fistula, they lead to severe hypertension and myocardial insufficiency, which requires surgical intervention.1 The preferred surgical approach to RAVF is endovascular embolization, but in a high-flow fistula, this treatment carries the risk of coil migration and systemic embolization. Case Report A 42-year-old man was admitted with chest pain, hypertension, and atrial fibrillation. The patient was addicted to cocaine. The physical examination, aside from cardiac enlargement and fibrillation, showed a continuous bruit in the right kidney area. Initially, a two-dimensional (2-D) echocardiography showed congestive cardiac failure with an ejection fraction of 38% and high flow through the right atrium, suggesting the presence of an arteriovenous fistula. A computed tomography (CT) scan (Figure 1) and a three–dimensional (3-D) reconstruction of the CT images (Figure 2) showed a 3.02-cm right renal arterial aneurysm with 2-cm uniform dilatation and a fusiform 7-cm mega cava engulfing the right renal vein and left renal vein (Figure 3). There were multiple dilatations of intrarenal arteriovenous malformations. A magnetic resonance imaging (MRI) scan (Figure 4) revealed a renal artery aneurysm with an inferior vena cava fistula (IVCF) and multiple peri-renal, arteriovenous, fistulous communications. A selective renal arteriography and a radioisotope scan showed 18% function in the right kidney. Because of the high flow through the fistula and the poor renal function, angioembolization was considered unsafe. The patient’s condition was optimized for surgery. Right nephrectomy was performed, and the fistula was ligated by suturing with 3/0 prolene and ligating with 2/0 silk suture. On the second postoperative day, anticoagulation therapy was begun because of the patient’s atrial fibrillation. The patient became hypotensive and underwent re-exploration, at which time the bleeding points were controlled by diathermy. The nephrectomy specimen showed the aneurysmally dilated renal artery with numerous large and torturous arteries and veins, confirming the arteriovenous malformation (Figures 5 and 6). He recovered and was discharged, resulting in an improved left ventricular end diastolic dimension and a controlled arrhythmia. Left ventricular dimension decreased from 7 to 6 cms postoperatively. There was no change in blood pressure in the immediate postoperative period. At 3-month follow up, the systolic pressure decreased by 30 mmHg and a diastolic pressure by 10 mmHg, showing a good outcome and a trend to normalization of the cardiac physiology. Discussion Among the vascular anomalies, renal artery aneurysms (RAA) and (RAVF) are relatively rare and have been infrequently described. RAA are reported to occur in only 0.1–1.3% of the population.2 RAVF are classified as acquired and congenital. They can be asymptomatic or present with a shunt, leading to high cardiac output, with hypertensive cardiopathy and congestive heart failure. The most common presentation, which occurs in 72% of cases, is severe hematuria as a result of erosion and hemorrhage into the urinary tract.3 Acquired RAVF are more common than congenital ones, occurring as a consequence of trauma, (posttraumatic vascular injuries) inflammation, or following percutaneous renal biopsy or earlier catheterization and nephrectomy. Congenital RAVF are the ones that most commonly cause heart failure. The incidence of congenital renal AV fistulas is about 0.04%; these fistulas constitute about 25% of RAVF.4 The exact mechanism of the formation of congenital RAVF is not known. Most of them are idiopathic, but there is evidence that congenital arteriovenous fistulas are the result of an eroding renal arterial aneurysm into an adjacent vein.1 Atherosclerosis and medial fibrodysplasia contribute to the occluding lesion within the renal artery, leading to formation of an aneurysm and subsequent arteriovenous fistulas. In 1934, Goldblatt established the pathophysiology of renovascular hypertension, showing that reduction in total blood flow because of the occluding process and the loss of pulsatile character in the artery cause the juxtaglomerular apparatus to secrete rennin.5 This, in turn, sets up the production of angiotensin, which leads to sustained elevation of the diastolic blood pressure that cannot be controlled by the usual forms of therapy.7 Our patient, who had no history of trauma, inflammation, or intervention on his kidneys, presented with diastolic congestive heart failure. It is likely that his high-output congestive cardiac failure was a result of the shunting of blood across the large arteriovenous fistula, which caused increased venous return and the elevated diastolic blood pressure due to relative renal ischemia. To evaluate such patients with suspected secondary hypertension, initial use of 2-D echocardiography can show the cardiac ejection fraction and can point toward the presence of a possible arteriovenous fistula. Imaging investigations such as CT scans and 3-D reconstruction of CT images can demonstrate anatomical communication of the renal aneurysm with adjacent veins or the inferior vena cava, which is useful information for planning the management. Magnetic resonance angiography (MRA) can also be used to localize RAVF. A radioisotope renal scan, which depends mostly on renal function, can help evaluate blood flow to the kidney. However, selective renal arteriography is to be the “gold standard” investigation for RAVF.7 Endovascular transcatheter embolization is the preferred method of managing RAVF, mostly because it is associated with low morbidity rate.8 In our patient who had a high-output fistula in the presence of a megacava, coil embolization presented a high risk of migration of embolic material through the fistula into the pulmonary arterial tree. To prevent that, procedures such as endovascular embolization with a partially deployed wall stent, vascular plug devices,9,10 and the “stop- flow” technique have been used.11 However, surgical correction is considered to be safer when, as in our patient, a high-output fistula exists in the presence of a megacava. Ligation of the fistula, resection and reconstruction by ex-vivo and in-vivo cold perfusion techniques are used to repair large renal artery aneurysms with an associated arteriovenous fistula.1 Previously, nephrectomy, partial or complete, was recommended for surgical treatment of RAVF,12,14 but embolization has now become the preferred initial intervention. In unstable patients who, like ours, have renovascular anatomy that is unfavorable for endovascular treatment, nephrectomy is a reasonable option. Conclusion Currently, endovascular embolization is the preferred initial method of managing RAVF, but this procedure presents an important risk for patients with giant renal arteriovenous high-output fistulas. This report confirms the safety of surgical intervention by means of nephrectomy and the ligation the RAVF in patients with unfavorable vascular anatomy. Acknowledgement We would like to thank you Masooma Niazi, MD, Department of Pathology, Naveen Pokala, MD, Department of Surgery from the Bronx-Lebanon Hospital Center for their advice in preparing this article.