Popliteal vein compression due to popliteal artery aneurysm: effects of aneurysm size.

Unlike the venous compression associated with larger popliteal artery aneurysms, which frequently is associated with deep vein thrombosis, the venous compression caused by the moderate sized (greater than 2 cm and less than 3 cm) aneurysms in the reported cases is not associated with thrombosis. The extrinsic compressive effect of these moderate sized popliteal artery aneurysms on the adjacent vein is shown to vary with the patient's leg position. Three of the four patients with unilateral leg swelling discussed here had bilateral popliteal artery aneurysms. In these cases, the contralateral leg had a small popliteal aneurysm (less than 2 cm) and no leg swelling was present. The cases suggest that popliteal artery aneurysm size is an important factor in determining the type of venous obstruction that results from the extrinsic compression of the ipsilateral popliteal vein. The described phenomenon of a popliteal artery aneurysm having the effect of restricting flow in the ipsilateral popliteal vein must be included as a differential diagnosis among the causes of unilateral leg swelling in the absence of deep vein thrombosis.