Origin and natural history of deep vein thrombosis of the legs.

Deep vein thrombosis (DVT) is a disorder frequently affecting the deep veins of the lower limbs; its onset is induced by known risk factors. The main complications of DVT are pulmonary embolism and postthrombotic syndrome (PST). Clinical pulmonary embolism occurs in a high proportion of cases of untreated proximal DVT and is associated with a mortality rate of 11-23% if not treated. PST, however, is a cause of increased morbidity and disability. The natural history of DVT is a dynamic process, with both thrombolysis and thrombus extension occurring after an episode of DVT. With the introduction of duplex scanning, several clinical studies have investigated and tried to clarify the natural history of DVT, the rate of recanalization of the thrombus, and the presence of reflux and its relation to lysis of the thrombus. These and other debated issues associated with PST are reviewed here. Knowledge of the evolution of these processes could result in better understanding of PST and be applied for improvement of medical and surgical management of venous thrombosis and its complications.