Animal models for epididymoepididymostomy. Development of an alternative microsurgical procedure for vasoepididymostomy.

The present success rate for high level microsurgical vasoepididymostomy in patients with obstructive azoospermia is generally poor in comparison with more distal vasoepididymal bypasses, suggesting that the development of a high level bypass method which preserves the distal maturation and storage functions of the epididymis might increase the fertility success rate. To achieve this we have developed a segmental bypass of the distal caput-proximal corpus regions of the epididymis (epididymoepididymostomy) using the rat and rabbit as animal models. In this procedure the epididymides of 11 adult male Sprague-Dawley rats were exposed through a scrotal incision and a convolution of the duct in the proximal corpus region was attached to an opened convolution in the mid-caput epididymides using a standard microsurgical technique. Each male was rested for at least 3 months after the microsurgical bypass operation to allow the preoperative sperm contents of the caudal storage region to be replaced by post-bypass spermatozoa. Six of the 11 rats were proven fertile after surgery by siring litters from mating trials up to 11 months later. The patency of anastomoses was confirmed in 3 animals by laparotomy and recovery of large numbers of sperm with normal motility from the cauda epididymidis distal to the anastomosis site and also from the vas. Similar unilateral surgery in 2 adult male rabbits resulted in normal post-operative semen profiles in 1 and an in vivo fertilisation rate of 100% from 1 mating trial 8 months after surgery. The successful development of a reliable animal model for epididymoepididymostomy provides an experimental tool for studying the function of the epididymis. This technique may also have clinical application as an alternative to high level vasoepididymostomy in selected patients with obstructive azoospermia.