The two most common causes of vasectomy failure are not using other methods of birth control in the first weeks or months following the procedure and spontaneous recanalization of the vas deferens. Generally, vasectomy is an extremely safe and reliable method of contraception. Though it can sometimes be reversed, vasectomy is a permanent procedure, making it a simpler and more reliable alternative to other methods of male and female contraceptives.
A vasectomy is a surgical procedure which snips and seals off tiny tubes called the vas deferens. The vas deferens take sperm from its production site in the testicles to the semen. When the vas deferens are cut, the sperm no longer make it to the semen so that, though the man can still ejaculate normally, his semen can no longer impregnate his sexual partner. The procedure takes between five to 20 minutes, depending on whether the patient chooses to undergo the no-incision or incision method of vasectomy. There are advantages and disadvantages to both methods, but both have an extremely low risk of vasectomy failure.
Though vasectomies are highly effective, it takes a while for all the sperm in the semen to be used up. Men may have to wait for weeks or months after the procedure to rely on the vasectomy as their only method of birth control. A semen analysis can tell the patient when all of the semen no longer contains sperm. Not waiting until all of the sperm has been cleared from the semen is the most common cause of vasectomy failure.
Though it is rare, the vas deferens can reconnect, or undergo spontaneous recanalization, and result in vasectomy failure in about one in a thousand cases. This usually happens in the first few months after the procedure, so the male often knows before he receives the go-ahead to have sex without another method of birth control that there has been a vasectomy failure. Recanalization can happen due to the formation of a sperm granuloma or scar tissue.
A sperm granuloma forms when sperm leaks out of the vasectomy site and causes an inflammatory reaction. Usually, this is not a problem, but in some cases, the granuloma evolves into a mass called a vasitis nosodum, which, in rare instances, can form a link between the two ends of the cut tubes. In rare cases, scar tissue can also join the ends of the tubes. Small canals can form in the scar tissue, allowing a small amount of sperm to pass through to the semen. Though fertility is much reduced, these complications can lead to vasectomy failure.
Vasectomy failure due to recanalization is often associated with a poor job on the part of the surgeon. Different methods of sealing of the ends of the vas deferens may also contribute vasectomy effectiveness in a small way. Though it is thought to be less comfortable than only sealing one end of the snipped tube, it may be more effective to close off both ends of the cut vas deferens. Cauterizing the tubes is also thought to be more reliable than tying off or clamping.