Role of epididymis in sperm maturation.

One hundred ninety patients with obstructive azoospermia caused by bilateral epididymal blockage have been followed up for four years or longer after undergoing "specific tubule" vasoepididymostomy. When anastomosis was required in the corpus epididymis, the "patency" rate was 78 percent, and the overall pregnancy rate was 56 percent. The pregnancy rate for "patent" cases was 72 percent, indicating that a high fertility rate can be obtained with sperm that have not transited the full length of corpus epididymis. By contrast, with vasoepididymostomy to the caput epididymis there was a 73 percent "patency" rate, but the overall pregnancy rate was only 31 percent. The pregnancy rate for "patent" cases was 43 percent. Sperm from the corpus epididymis have a higher rate of fertility than sperm from the caput epididymis, but sperm from proximal areas of the corpus have no less fertility than sperm from the distal corpus epididymis. The most remarkable observation is that in almost half the cases sperm that have never journeyed beyond the caput epididymis seem to be capable of causing pregnancy.