Anatomical sizes of the human vas deferens after vasectomy.

After vasectomy, the lumen of the testicular side of the vas deferens dilates, apparently because of internal pressure from accumulation of spermatic fluid. This dilatation occurs within the 1st postoperative year. It causes a thinning of the wall of the vas without significant increase in the external diameter. The extent of dilatation is similar in the same man, but differs markedly between individuals, the mean increase in diameter being approximately 70%. The implications of this difference in size are discussed with regard to vas anastomosis and to the possible use of devices to rejoin the vas or to bridge a defect created by a prior vasectomy.