Incidental discovery of a long standing arteriovenous fistula after thrombectomy for acute lower limb ischaemia.

INTRODUCTION: Arteriovenous fistula (AVF) is the abnormal connection between an artery and vein. Congenital AVF of the popliteal artery is very rare.

PRESENTATION OF CASE: 89 year old lady presented with right acute lower limb ischaemia. She had unilateral chronic venous hypertensive change in the right leg. Femoral embolectomy was performed. Backflow was achieved. Arteriotomy was closed. The patient's leg continued to deteriorate. She returned to theatre. On-table angiogram showed an occluded SFA. Thrombectomy was completed. SFA was patent but no blood flowed into the distal popliteal artery. A second on table angiogram revealed AVF between popliteal artery and vein. Dissection to the posterior aspect of the knee revealed the fistula. The vein was arterialized and enlarged. The AVF was ligated. Normal distal blood flow was achieved. Retrospectively we measured the leg lengths. Right leg was 3cm longer than the left. The right leg circumference was 7cm greater than the left. She reported chronic venous change from a young age. She did not report any history of trauma to the limb.

DISCUSSION: Popliteal artery to popliteal vein fistula is a rare. Trauma is the most common cause of popliteal AVF. Should the condition develop before closure of the epiphyses, there may be an increase in leg measurements.

CONCLUSION: We postulate that this case of AV fistula may be congenital due to discrepancy in leg measurements and unilateral chronic venous hypertensive change. Rarely persistent remnants of the embryonic sciatic artery can lead to arteriovenous anastomoses, which may be a possible aetiology.