Thrombosis occurs frequently in thromboangiitis obliterans (Buerger's disease) in which of the following vessels?

B. Radial or ulnar artery.

C. Digital arteries.

D. Superficial veins.

DISCUSSION: Thromboangiitis obliterans is characterized by thrombosis and inflammation of small and medium-sized peripheral arteries and veins, and by migratory superficial phlebitis. Unlike atherosclerosis, it often involves the upper extremity. Thromboangiitis obliterans rarely involves large vessels such as the brachial or femoral arteries.