Venous ulcers: pathophysiology and medical therapy. Venous ulcers may occur as a result of lower extremity calf pump failure, with ensuing edema, trapping of white blood cells and deposition of pericapillary fibrin. Acute, smaller lesions are easily treated with adequate compression and occlusive dressings. Larger, more chronic wounds often benefit from some form of external compression. Occlusive dressings and local wound care are most effective when used simultaneously with compression. Sequential compression pumps merit study and may prove to be of therapeutic and prophylactic value. In refractory cases, long-term use of compression devices may be required to prevent ulcer recurrence. 