Vasectomy is a surgical procedure in which the vasa deferentia of a man are cut for the purpose of sterilization. There are some variations on the procedure such as no-scalpel (keyhole) vasectomies, ^[2] in which a surgical hook, rather than a scalpel, is used to enter the scrotum. Another type of vasectomy which may reduce the risk of chronic pain could be the so-called "open ended" vasectomy. A "normal" vasectomy typically seals both ends of the vas deferens with stitches, heat, or both, after cutting. The open-ended vasectomy seals only the top end of the vas. With this method sperm are free to spill out from the lower severed end of the vas thus avoiding any build-up of pressure. The likelihood of long-term testicular pain from "backup pressure" seems to be eliminated using this method.

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 bloodstream. ^[3]

^[4] The sperm-filled fluid from the testes contributes about 10% to the volume of an ejaculation (in men who are not vasectomized) and does not significantly affect the appearance, texture, smell or flavor of the ejaculate ^[5]. There are anectdotal reports regarding volume of ejaculate being much diminished, regardless of the actual quantity of semen that is blocked off. This is not entirely understood.

When the vasectomy is complete, sperm can no longer exit the body through the penis. They are 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 macrophages and re-absorbed via the blood stream. Sperm is matured in the epididymis for about a month once it leaves the testicles. Approximately 50% of the sperm produced never make it to ejaculation in a non-vasectomized man. After vasectomy, the membranes increase in size to absorb more fluid, and more macrophages are recruited to break down and re-absorb more of the solid content. The fraction of sperms that exceed the digestive capabilities of macrophages exit into the scrotum as sperm granulomas.