Surgical Treatment of a Giant External-Iliac-Vein Aneurysm in a Patient with a Post-Traumatic Femoral Arteriovenous Fistula

Abstract

Iliac vein aneurysm is a rare vascular abnormality. It has been reported as a primary aneurysm of unknown cause, or, when a cause could be identified, as a secondary iliac vein aneurysm. Occasionally, iliac vein aneurysm develops in association with distal arteriovenous fistula. Although venous aneurysms occur most commonly in the neck and central thoracic veins, they also have been reported in the visceral veins and the extremities.

Herein, we present the case of a 34-year-old man in whom a giant external-iliac-vein aneurysm was incidentally found during the investigation of a post-traumatic femoral arteriovenous fistula. The aneurysm was surgically resected, the iliac vein was reconstructed by means of lateral venorrhaphy, and the patient had an uneventful, complete recovery. We discuss the origin of the aneurysm and our choice of surgical techniques.

Aneurysms of the iliac vein are rare. They can occur in association with arteriovenous fistulae that are located elsewhere.¹ Venous aneurysms occur most commonly in the neck and central thoracic veins, and they have also been discovered in the visceral veins and the extremities. However, there are few reports of iliac vein aneurysms²—formations that are subject to thromboembolism or rupture.³ Herein, we present the case of a patient in whom a giant external-iliac-vein aneurysm developed consequent to a post-traumatic femoral arteriovenous fistula.

Case Report

A 34-year-old man had sustained a gunshot injury to his left leg at age 19 years. He recovered fully and had noticed no sequelae of the trauma during the 15 years thereafter. In February 2009, he was admitted to our clinic because of swelling and numbness in his left leg. Physical examination revealed a larger diameter of the left lower limb than the right. Multiple scars were visible on the lower third of the left thigh. The left leg was slightly warmer than the right, and the peripheral pulses were equally palpable. A thrill was felt and a murmur was heard on the injured area. Doppler ultrasonography revealed a high-velocity arteriovenous fistula at the distal femoral artery. The left superficial femoral artery was larger than the right (diameter, 1.9 vs 0.9 cm). Angiographic examination showed an arteriovenous fistula at the level of the distal third of the superficial femoral artery, along with a giant aneurysm of the left iliac vein (Figs. 1 and 2A). Multislice computed tomography identified a giant, nonthrombotic aneurysm of the left external iliac vein (Figs. 2B and 2C). Transthoracic echocardiography revealed normal left ventricular systolic and diastolic function. The patient was scheduled for surgery.

Fig. 1 Angiography shows the arteriovenous fistula (circled).

Fig. 2 A) Angiography shows the left external iliac vein aneurysm (arrow). Multislice computed tomograms show the aneurysm in B) axial view (arrow) and C) sagittal view (circle).

Surgical Technique

The patient was placed under endotracheal general anesthesia, in supine position, with a hard pillow under the left lumbar region. A vertical left inguinal incision was made. Then, the femoral artery and femoral vein were separated with the use of vessel loops. The arteriovenous fistula between those vessels was exposed. After the systemic injection of 3,000 units of heparin, the femoral artery and vein were clamped proximally and distally. The arteriovenous fistula was separated, lateral repair of the femoral vein was completed, and end-to-end anastomosis of the femoral artery was performed. Then, a left-flank incision for a retroperitoneal approach was made, in order to reach the left inguinal incision. The retroperitoneal space was entered, and the aneurysmal sac was dissected free from all surrounding tissue. Its proximal and distal necks were exposed. The left iliac vein was dilated and kinked, which compressed the external iliac vein proximally (Fig. 3). After the necks of the aneurysm were controlled with vessel loops, the aneurysm was clamped proximally and distally. No thrombus was seen in the aneurysm when it was opened. A vascular clamp was placed tangentially, and the aneurysm was resected. After the clamp was removed, lateral venorrhaphy was performed with use of a continuous 5-0 polypropylene suture (Fig. 4). The specimen from the venous wall was sent for histopathologic examination.

Fig. 3 Intraoperative photograph shows the left external iliac vein aneurysm.

Fig. 4 Intraoperative photographs show A) the tangential clamping and venotomy, and B) the venorrhaphy.

During the uneventful postoperative period, the patient was given heparin for 4 days. Histopathologic examination of the resected venous sections revealed an increase in fibrous connective tissue of the venous wall (Fig. 5). Upon the patient's discharge from the hospital after 5 days, he was prescribed oral warfarin for 1 year and was advised to wear elastic stockings for 1 month. At the 6-month follow-up examination, the patient was asymptomatic, and venous Doppler ultrasonography showed normal calibration of the iliac vein.

Fig. 5 Photomicrograph shows an increase in fibrous connective tissue of the venous wall (H & E, orig. ×100).

Discussion

Iliac vein aneurysms are rare vascular abnormalities that have been reported as primary aneurysms with an unknown cause, or, when a cause has been identified, as secondary iliac vein aneurysms. Iliac vein aneurysms occasionally have been found in association with a distal arteriovenous fistula.^4,5 Clinical symptoms of iliac vein aneurysms develop after local thrombosis, thromboembolism, compression of the pelvic structures, or rupture of the aneurysm.⁴ Our patient had no symptoms from the aneurysm, which we identified coincidentally during our angiographic examination of the arteriovenous fistula.

The pathophysiology of iliac-vein-aneurysm formation due to an arteriovenous fistula is unclear. Apparently, increased arterial flow with subsequent arterial dilation proximal to the fistula plays a crucial role. The arterial dilation results in compression of the ipsilateral iliac vein, which leads to a hemodynamically significant outflow obstruction that results in venous hypertension. Over time, altered venous pressure and flow may stretch the venous wall sufficiently to cause the development of an iliac vein aneurysm.⁴

There are few published reports of iliac vein aneurysm after an untreated arteriovenous fistula. The aneurysm probably develops due to compression of the iliac artery, which is dilated because of the chronically untreated femoral arteriovenous fistula to the iliac vein. Our patient participated in scuba diving almost every day. We believe that his aneurysm developed because the iliac artery became dilated due to increased arterial blood flow from exercise and compression of the iliac vein. In fact, the left external iliac artery was profoundly dilated and kinked, which was compressing the patient's external iliac vein. The aneurysm developed distal to this compression.

Surgical procedures such as ligation, tangential excision with lateral venorrhaphy or an autologous vein patch, and resection with reconstruction have all been advocated as definitive treatments.^2,6 Resection with end-to-end anastomosis can be performed in selected instances. Because simple ligation of the iliac vein predisposes the patient to post-thrombotic leg syndrome, venous reconstruction is warranted after the aneurysm is resected.⁷

Prosthetic and autologous vein grafts can be used in the reconstruction of an iliac vein aneurysm. Disadvantages of prosthetic grafts include thrombogenicity, poor long-term patency rates after venous reconstruction, and the possible formation of additional fistulae. Finding an autologous vein graft of the same size is not always possible, and the search can prolong the operation. Therefore, we preferred to perform the lateral venorrhaphy, without using prosthetic material or an autologous vein. We created a new vein from the remaining venous wall after resecting the aneurysm. In general, we think that this procedure is more physiologically viable than the alternatives.

The common histologic appearance of a venous aneurysm is a thickened, fibrotic intima with medial thinning caused by a decrease in the number of medial smooth-muscle cells.² In one of the earliest reports of venous aneurysms, Schatz and Fine⁸ described multiple histopathologic findings. One common finding is a reduction of smooth-muscle cells and an increase in fibrous connective tissue; another is either an increase or a decrease in the fibrous connective tissue and elastic fibers.⁹ In our patient's case, histologic examination revealed an increase in fibrous connective tissue of the venous wall.

On the basis of the successful outcome, we conclude that it was appropriate to excise the fistula, resect the aneurysm, and reconstruct the iliac vein by means of lateral venorrhaphy in a single surgical session.