SciTech

How does a vasectomy work?

Dr. David Sokal is a scientist at Family Health International and a member of the American Urological Association panel in charge of developing vasectomy guidelines for U.S. surgeons.
Dr. David Sokal is a scientist at Family Health International and a member of the American Urological Association panel in charge of developing vasectomy guidelines for U.S. surgeons.

Dr. David Sokal is a scientist at FHI 360, a public health and development organization headquartered in Research Triangle Park. He is a member of the American Urological Association panel in charge of developing vasectomy guidelines for U.S. surgeons. Here he explains the biology behind vasectomies. Questions and answers have been edited.

Q: Could you explain how a vasectomy works?

The word vasectomy is from Latin and means “cutting (ectomy) of the vas,” where vas is short for vas deferens. The vas deferens is the tube that carries sperm from the testes into the body, where the sperm mix with secretions from the seminal vesicles and prostate gland to form semen. Most of the semen is from the seminal vesicles and the prostate gland. By cutting the vas, a vasectomy keeps the sperm from getting into the semen.

Q: Is a vasectomy 100 percent effective?

For most men it is, but no contraceptive method is 100 percent effective. Doctors recommend a semen analysis after a vasectomy, to make sure that it was successful. However, every once in a while – even months or years later – the body repairs the cut vas, and a man’s partner becomes pregnant. It is estimated that this happens after about 1 in 2,000 vasectomies. However, a vasectomy is more reliable than any reversible contraceptive; and compared to “tying the tubes” – female sterilization – vasectomy is just as effective, and is simpler, faster and safer.

Q: If the procedure doesn’t stop the production of sperm, where do sperm go?

After a vasectomy, the sperm build up in the epididymis, eventually disintegrate, and are absorbed by the body. This is similar to what happens to sperm if a man does not ejaculate for a while. However, this accumulation of sperm can sometimes result in pain. Estimates vary, but some experts think as many as 2 percent of men may have significant long-lasting pain after vasectomy. Other experts think the rate is closer to 1-in-1,000 men. This pain is usually treated successfully with over-the-counter medicines like ibuprofen or naproxen.

Q: Will a man be able to notice a difference when he has sex after a vasectomy?

Sperm only make up about 3 percent of the semen, so differences are unlikely to be noticed after vasectomy. Also, since a vasectomy does not have an effect on the testes’ production of testosterone – the male hormone – men’s sexual desires do not change. A study of more than 3,000 men in Australia in 2010 confirmed earlier research, finding no difference in sexual issues between men who had or had not had a vasectomy.

The lead scientist of that study, Anthony Smith, Ph.D., also noted that many men report that sexual enjoyment is increased after a vasectomy because the man and his partner no longer have to worry about the risk of pregnancy.

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