Aneurysms of the inferior vena cava

Aneurysms of the inferior vena cava are very rare. We describe a case of a saccular aneurysm of the inferior vena cava that thrombosed after vigorous exercise. This presented as deep venous thrombosis associated with a retroperitoneal mass. Laparotomy with biopsy confirmed the benign nature of this lesion, and symptoms gradually resolved. It is hypothesized that the increased intraabdominal pressure during exercise led to the thrombosis of what is presumed to be a congenital aneurysm of the inferior vena cava.