The connection between occurrence of thrombi in the deep venous system of the lower limbs and the development of pulmonary emboli has been firmly established. Venous thrombosis can involve the superficial leg veins, the deep veins of the calf, and deep veins above the knee, with the greatest risk of adverse sequelae associated with thrombi found in the popliteal, femoral, and iliac veins.
While estimates of the attack rates of venous thromboembolism vary widely depending on the characteristics of the study population and diagnostic criteria employed, pulmonary embolism continues to be a major cause of hospital mortality with at least 50 000 and upward of perhaps 200 000 deaths on an annual basis in the United States. While deep venous thrombosis and pulmonary embolism usually complicate the course of hospitalized patients, recent data suggest that venous thrombi may also affect ambulant and otherwise healthy individuals, though to a considerably lesser
Goldberg RJ. Venous Thromboembolism and Malignancy. Arch Intern Med. 1987;147(11):1893-1894. doi:10.1001/archinte.1987.00370110021002