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Vasectomy is a surgical procedure for male sterilization and/or permanent contraception. During the procedure, the male vas deferens are severed and then tied/sealed in a manner so as to prevent sperm from entering into the seminal stream (ejaculate) and thereby prevent fertilization. Vasectomies are usually performed in a physician's office, medical clinic, or, when performed on an animal, in a veterinary clinic— hospitalization is not normally required as the procedure is not complicated, the incisions small, and the necessary equipment routine. There are several methods by which a surgeon might complete a vasectomy procedure, all of which occlude (i.e. "seal") at least one side of each vas deferens. To help reduce anxiety and increase patient comfort, men who have an aversion to needles may consider a "''no-needle''" application of anesthesia while the "''no-scalpel''" or "''open-ended''" techniques help to accelerate recovery times and increase the chance of healthy recovery. Due to the simplicity of the surgery, a vasectomy usually takes less than thirty minutes to complete. After a short recovery at the doctor's office (usually less than an hour), the patient is sent home to rest. Because the procedure is minimally invasive, many vasectomy patients find that they can resume their typical sexual behavior within a week, and do so with little or no discomfort. Because the procedure is considered a permanent method of contraception and is not easily reversed, men are usually counseled/advised to consider how the long-term outcome of a vasectomy might affect them both emotionally and physically. The procedure is not often encouraged for young single men as their chances for biological parenthood are thereby more or less permanently reduced to almost zero by it. It is seldom performed on dogs (castration, a different procedure, remains the preferred reproductive control option for canines) but is regularly performed on bulls. ==Medical uses== A vasectomy is done to prevent fertility in males. it ensures that in most cases the person will be sterile after confirmation of success following surgery. The procedure is regarded as permanent because vasectomy reversal is costly and often does not restore the male's sperm count and/or sperm motility to prevasectomy levels.Men with vasectomies have a very small (nearly zero) chance of successfully impregnating a woman, but a vasectomy has no effect on rates of sexually transmitted infections. After vasectomy, the testes remain in the scrotum where Leydig cells continue to produce testosterone and other male hormones that continue to be secreted into the blood-stream. Some studies have found that sexual desire after vasectomy may be somewhat diminished.〔〔 When the vasectomy is complete, sperm can not exit the body through the penis. Sperm are still produced by the testicles, but they are soon broken down and absorbed by the body. Much fluid content is absorbed by membranes in the epididymis, and much solid content is broken down by the responding macrophages and reabsorbed via the blood stream. Sperm is matured in the epididymis for about a month before leaving the testicles. After vasectomy, the membranes must increase in size to absorb and store more fluid; this triggering of the immune system causes more macrophages to be recruited to break down and reabsorb more solid content. Within one year after vasectomy, sixty to seventy per cent of vasectomized men develop antisperm antibodies.〔 In some cases, vasitis nodosa, a benign proliferation of the ductular epithelium, can also result.〔〔 The accumulation of sperm increases pressure in the vas deferens and epididymis. The entry of the sperm into the scrotum can cause sperm granulomas to be formed by the body to contain and absorb the sperm which the body will treat as a foreign biological substance (much like a virus or bacterium).〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Vasectomy」の詳細全文を読む スポンサード リンク
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