In Buerger's disease all of the following are affected, EXCEPT:

Buerger's disease is a rare, segmental, nonatherosclerotic, inflammatory occlusive disease that commonly affects small and medium sized aeries, veins and nerves of the extremities. The clinical features of thromboangiitis obliterans includes a triad of claudication of the affected extremity, Raynaud's phenomenon, and migratory superficial vein thrombophlebitis. Claudication affects calves and feet or forearms and hand. Due to severe digital ischemia, trophic nail changes, painful ulcerations, and gangrene may develop at the tips of the fingers or toes. On examination there is normal brachial and popliteal pulses but reduced or absent radial, ulnar, and/or tibial pulses. Investigation: Aeriography shows smooth, tapering segmental lesions in the distal vessels and presence of collateral vessels at sites of vascular occlusion. The diagnosis can be confirmed by excisional biopsy and pathologic examination of an involved vessel. Ref: Ferri's Clinical Advisor 2012 E-Book: 5 Books in 1 ; Expe Consult, page 1007 ; Harrisons Principles of Internal Medicine, 18th edn, chapter 249