Abstract

Venous thrombosis and pulmonary embolism are serious hazards after operations and trauma, in childbirth, and in a variety of medical conditions including cardiac failure and infarction. Almost half the patients have no clinical signs or symptoms of the thrombosis itself, and fatal pulmonary embolism may occur without warning.¹ Pulmonary embolism occurs in almost 50% of patients with thrombosis of a popliteal, femoral or iliac vein; it is less common and rarely of clinical significance if only the calf veins are involved,^2–4 and this is so in 85% of all deep-vein thromboses.⁵ Most deep veins recanalise after thrombosis, but often the valves in the main veins and ankle-perforating veins are left incompetent, leading to the post-phlebitic syndrome of venous hypertension, capillary dilatation, swelling and eventually tissue necrosis with ulceration.⁶