Abstract

A 41-year-old male with a large arteriovenous fistula (AVF) of the left iliac vessels was referred to our clinic. Patient had a gunshot wound to the abdomen 10 years ago and underwent colostomia and repairment of the left iliac vein. The patient had been on oral anticoagulant therapy since he underwent aortic valve replacement 5 years ago. Covered endovascular stent grafts could not be used due to big size discrepancy between the common and external iliac arteries. Simple embolization with a detachable balloon system and placement of a stent to stabilize the balloon resulted with failure. AVF was closed surgically. Although endovascular approaches offer great advantages for the treatment of complex vascular pathologies, surgery remains the ultimate solution as in this case.

Iatrogenic iliac arteriovenous fistula (AVF) is a wellknown complication of lumbar disc surgery. There have been numerous case reports regarding its surgical and endovascular treatment.[1,2] However, posttraumatic iliac AVF involving the internal iliac artery and the external and/or internal vein are extremely rare.[3] Their treatment is more complicated since they are more chronic and most patients have already undergone one or more laparotomies to repair other organ damages caused by missile injury. We report the management of a patient with chronic posttraumatic iliac AVF.

Case Presentation

A 41-year-old male complaining of left leg swelling and fatigue was referred to our clinic with the diagnosis of large AVF of the left iliac vessels. Patient had a gunshot wound to the lower abdomen 10 years ago. Patient underwent colostomy, repair of left iliac vein injury and left nephrectomy. Later, the colostomy was closed on an elective basis. The patient also underwent aortic valve replacement with a mechanical prosthesis 5 years ago and has been on oral anticoagulation since then.

On physical examination, a loud bruit was audible in the left lower quadrant. The patient had signs of chronic venous insufficiency of the left lower extremity. Digital subtraction angiography revealed a large side wall arteriovenous fistula between the proximal portion of the left internal iliac artery and the vein (Fig. 1). A bullet was located near the AVF on posteroanterior projection. The left common and internal iliac arteries became enlarged and were measured 20 and 12 mm in diameter, respectively. The left external iliac artery diameter was only 7 mm. A large venous aneurysm filling the entire pelvis was seen on a CAT scan study (Fig. 2).

Fig 1: Digital subtraction angiography showing a large side wall arteriovenous fistula between the proximal portion of the left internal iliac artery and the iliac veins.

Fig 2: A large venous aneurysm on a Computed axial tomography scan study.

Management. Oral anticoagulant was discontinued and low molecular weight heparin q12h was started. Since the patient underwent multiple laparotomies and had to be on anticoagulant therapy, it was deemed better if the fistula could be closed by means of endovascular techniques.

Endovascular approach. A detachable silicon balloon (Goldvalve Balloon, Paris, France ) with a diameter of 14 mm and a length of 22.5 mm was used to occlude the arteriovenous communication and the left internal iliac artery simultaneously. The balloon was inserted through the contralateral common femoral artery and was inflated with isotonic contrast medium at the ostium of internal iliac artery. Several attempts were made to position the balloon to occlude the communication. The maximum recommended volume of contrast injection was reached and the balloon occluded the left internal iliac artery and the AVF, however the sump effect of low-pressure venous side caused the transition of the balloon into the venous aneurysm through its shortest diameter. Despite the use of maximum balloon size available, simple embolization with a detachable balloon system resulted in failure. The balloon was deflated and retrieved in order not to give rise to pulmonary embolism. We thougt that implantation of a self expandable nitinol stent (Biotronik, Berlin, Germany) could stabilize the balloon in the internal iliac artery. For this purpose, a 1 cm wide and 4 cm long stent was implanted in the proximal segment of the internal iliac artery. Afterwards, a detachable silicon balloon was implanted in the stent lumen and was inflated until the maximum size was reached. The balloon stayed in the lumen of the internal iliac artery with the support of the stent and occluded the AVF (Fig. 3). The common and external iliac arteries were patent whereas the internal iliac artery and AVF were completely occluded. No retrograde filling of the AVF was seen an control angiography and the balloon was left in place without any complication. However, 24 hours later, the abdominal bruit returned as an indicator of recanalization. Repeat anjiography revealed rupture of the balloon and recanalization of the AVF. Another balloon was placed and the AVF was occluded in the same manner. This also resulted in failure within two days. Patient was prepared for surgery.

Fig 3: Angiogram showing the occlusion of the arteriovenous fistula by the balloon staying in the lumen of the internal iliac artery with the support of a stent.

Surgical technique. After a midline laparotomy and release of dense adhesions, bowels were mobilized. Large venous aneurysm filling the small pelvis was seen. Inferior vena cava and iliac veins were pulsatile. Distal abdominal aorta, left common and external iliac arteries were freed and looped with a vascular tape (Fig. 4). Fistula orifice was located at the proximal portion of the left internal iliac artery, 1 cm distal from the bifurcation. This portion of the artery could be dissected free with the scalpel due to dense adhesions. Intermittant clamping of the left common iliac artery to reduce the pressure and volume in the venous aneurysm revealed better exposure. Distal portion of the internal iliac artery could not be reached since it was embedded to the wall of the venous aneurysm. After heparinization, left common and external iliac arteries were clamped. Short proximal neck of the internal iliac artery could be clamped over the previously placed stent. This artery was amputated by leaving a small rim of wall and the defect at the bifurcation was primarily closed by linear suturing. Stent was quickly removed during a brief period of declamping. It was noted that the thrill over the fistula was still present. The portion of the internal iliac artery distal to the fistula was carved out by scalpel.

Fig 4: Operative view of the left iliac bifurcation and the venous aneurysm. The left common and external iliac arteries were freed and looped.

Thrill disappeared after ligation of this segment of the artery. Piece of the internal iliac artery that includes the fistula orifice was oversewn from outside. The venous aneurysm that mainly originated from the left internal iliac vein was left in place for the venous drainage of the left leg since it also constituted a long segment wall of the external iliac vein.

Postoperative course of the patient was uneventful, and his left leg swelling and venous engorgement disappeared dramatically.

Comment. The aim of the endovascular treatment must be the occlusion of the fistula with preservation of distal flow. At present, covered endovascular stent grafts are best suited for this purpose. However, in our case there was a big discrepancy between the diameters of the common iliac, and external iliac artery diameters. In addition, the AVF was located close to the internal iliac artery ostium. Endograft implantation was not suitable in this case due to above-mentioned factors. Theoretically, a tapered-graft of appropriate size could have been used. Placement of a detachable balloon was unsafe, also due to the location of the AVF. Use of a self expandable nitinol stent to stabilize the detachable balloon was not successful. The failure could be attributed to the sharp stent struts causing rupture of the silicon balloon.

Although it was used for nephrectomy in this patient, one could consider using a retroperitoneal approach to avoid intraperitoneal adhesions. We preferred midline incision since the distal aorta, and especially the pulsatile inferior vena cava and proximal iliac veins could be safely controlled in case of an inadvertent entry to these vessels.

Venous aneurysms are rare and their long term behavior is unknown due to lack of large series. Their known risks of embolism and thrombosis can be reduced by lifelong intake of oral anticoagulants.[4] Intervention was advocated in symptomatic or enlarging ones.[5] There are only a couple of case reports with good surgical outcome in primary venous aneurysms. In these reports either a PTFE or an autologus vein was used for venous reconstruction.[4,6] In our case, the venous aneursym was not resected due to a couple of reasons. Aneurysm did not have a neck and rather constituted a long segment wall of the external iliac vein. As mentioned above, long term patency of grafts on the venous system is not clear. One would expect stability or regression of the secondary venous aneurysm after cessation of the arterial pressure and flow pattern. We believe it is safe to follow the venous aneurysm in this case by means of yearly CAT scan or sonographic imaging since the patient had to take lifelong oral anticoagulant for the mechanical heart valve prosthesis anyway. The size of the venous aneurysm in our patient was found to be slightly diminished in a follow-up sonogram which was done 2 months after the surgery.

Although endovascular approaches offer great advantages for the treatment of complex vascular pathologies at difficult locations such as posttravmatic iliac AVF, surgery remains the ultimate solution as in this case.