Obstructive azoospermia of unknown origin: sites of obstruction and surgical outcomes.

Although the majority of patients with obstructive azoospermia have medical histories or signs related to seminal tract obstruction, the pathogenesis of the obstruction is unknown in some patients. Of 38 patients with obstructive azoospermia treated at our hospital preoperative data did not indicate causes or sites of obstruction in 6. Operative and pathological findings showed obstruction at the proximal convoluted vas deferens or between the most distal portion of the cauda epididymis and the vas deferens in 8 of 11 blocked seminal tracts. Microsurgical epididymovasostomy resulted in a patent anastomosis in all 6 patients and pregnancy in 2. In patients with obstructive azoospermia of obscure preoperative causes, it is highly probable that the obstruction sites are in the convoluted vas deferens or the transitional region between the cauda epididymis and vas deferens, and that fertility may be restored by microsurgical epididymovasostomy.