Ischemic forms of acute venous thrombosis.

Venous thrombosis in an extremity, when extensive, can cause reversible tissue ischemia or frank gangrene even without arterial or capillary occlusion. Patients gradually or abruptly develop severe pain, extensive edema, and cyanosis of the extremity, nearly always in the legs. Gangrene can occur unless the venous obstruction is relieved. Such ischemic venous thrombosis can complicate surgery, trauma, childbirth, or prolonged immobility, but malignant neoplasms, either obvious or occult, are a major predisposing factor. The optimal therapy is anticoagulation and thrombectomy. Patients with venous gangrene may require amputation if extensive, deep-tissue destruction occurs. The mortality rate for ischemic venous thrombosis is about 40%, the cause of death usually being the underlying disease or pulmonary emboli.