A vagotomy is a surgical procedure that is performed only in humans. It is resection (removal of, or at least severing) of part of the vagus nerve. It is not to be confused with vasectomy.

A plain vagotomy is a very destructive procedure, since all the parasympathetic supply from the stomach to the left side of the transverse colon relies on the vagus nerves. The gut will still function without vagus supply, but not as well.

Vagotomy technique was therefore improved by restricting resection to only those branches that go to the stomach (selective vagotomy), and further by selecting only those branches that appear to supply peptic cells (highly selective vagotomy).

Humans have two vagus nerves, whose fibres decussate and intermingle around the stomach. Accordingly, a vagotomy operates on both nerves simultaneously and in practice there is no need or way to make a distinction between them.

From http://en.wikipedia.org/wiki/Vagotomy