Transcutaneous male sterilization.

ABSTRACT

PIP This report reviews and summarizes the results of current animal and human research studies for each of the 3 approaches to transcutaneous sterilization intratesticular injection of chemical agents to affect spermatogenesis; intraepididymal injection of chemical agents to affect sperm transport; and obstruction of the vas lumen by the intravasal injection of chemical (sclerosing) agents or by electrocoagulation of the vas lumen. Wiebe and Barr evaluated the effects of the direct injection of aqueous 1, 2, 3-trihydroxypropane (THP; glycerol), a normal component of living cells, into the testes of Sprague-Dawley rats. Spermatogenesis was inhibited by a direct and local action of THP on the seminiferous tubules. The only other intratesticular method that has been investigated is the use of ultrasonic energy. Although the injection of sclerosing agents directly into the epididymis is technically simpler than injection into the vas lumen, the intraepididymal approach to nonsurgical sterilization has been evaluated in only 3 studies. The advantages of intraepididymal over intravasal injections are that the cauda epididymis is easily palpated and intraluminal placement of the needle in the epididymis is not necessary. The appeal of the intraepididymal approach to transcutaneous sterilization is that it is easier to inject a chemical into the epididymis than into the vas lumen. Limitated evaluations of the intraepididymal injection of chemical agents has shown this to be an unsatisfactory approach to male sterilization. Whether improved results can be obtained with other chemical agents remains to be evaluated. Numerous chemical agents have been injected into the vasa of rats, dogs, and rabbits to evaluate their effects in producing vas occulsion. A table lists the agents that have been evaluated. Only 2 chemical agents are known to have been tested in man 3.6% formaldehyde in 90% ethanol and 4% formaldehyde in 90% ethanol and a carbolic acid, n-butyl alpha cyanoacrylate mixture. The mode of action of all of the sclerosing agents tested is thought to be similar they produce local necrosis and fibrosis and vasal closure through scarring. A main objective in choosing a chemical agent for use in human sterilization procedures is to select one that has minimal toxic effects and will produce a minimal amount of damage if injected onto structures other than the vas. The transcutaneous intravasal sterilization procedure developed by the Chinese and which has been widely and successfully used since 1972 is described. To further advance the electrocoagulation procedure developed by Schmidt in 1966, bipolar electrodes have been developed. Black, at the Marie Stopes Clinic in the UK, is currently investigating a transcutaneous electrocoagulation procedure. Black believes that improvement of the electrodes and some changes in the technique of performing the electrocoagulation will result in an effective procedure.^ieng