male sterilization by surgical excision of the vas deferens, the thin duct that carries sperm cells from the testicles to the prostate and the penis. Vasectomy is a popular method of birth control : in 1983, figures showed that approximately 10 million men had been sterilized in the U.S. since 1969. Excision of the vas deferens is a minor surgical procedure that can be performed in a physician's office in less than half an hour. A small incision is made on one side of the scrotum (the external sac housing the testes) and the vas deferens is located, cut, and the ends tied off. The incision is closed and the procedure is repeated on the other side. After surgery, it is necessary to wait until a negative sperm count is obtained before discarding other means of contraception, because viable sperm cells are retained in the seminal vesicles (the pair of storage pouches where sperm is mixed with other components of semen) and along the various sperm ducts. In addition it is usually advised that the patient be reexamined after a year, because the severed ends of the vas deferens occasionally reknit. Sterility resulting from vasectomy is considered to be permanent, and attempts at surgically reversing vasectomy, called vasovasotomy, have had limited success. In India, where the government is trying to stem the tide of overpopulation, money is paid to men who submit to voluntary vasectomy. Efforts to overcome the irreversibility of vasectomy have also led to experimentation with the implantation of faucetlike devices that can be made to open or close the sperm duct in a simple operation. Such devices have functioned successfully in animals but are still considered experimental in humans because of their unproved reversibility, high cost, and the degree of surgical skill needed to implant them. Another option suggested to those undergoing vasectomy is to preserve their fertility by depositing semen in sperm banks. Such semen samples are frozen in liquid nitrogen below −300 degrees Fahrenheit (−185 degrees Fahrenheit) and are considered to be viable for an indefinite period. However, there is considerable debate over the scientific and ethical aspects of sperm freezing, and the practice is still considered experimental. Researchers have examined the possible negative physiological effects of vasectomy, but there is no conclusive evidence that any link exists between the procedure and disease.

See S. D. Mumford, Vasectomy: The Decision-Making Process (1978); G. Denniston, Understanding Vasectomy (1978).

The Columbia Encyclopedia, Sixth Edition Copyright© 2004, Columbia University Press. Licensed from Lernout & Hauspie Speech Products N.V. All rights reserved.

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