The diseased colon (or part of it) is removed in a procedure that's called a colectomy (removal of colon). The colon is cut from the healthy small intestine and a portion of the tissue in the rectal area is left. The amount of tissue left in the rectal area depends on the extent of the disease.

This is a major part of the operation because the colon has many adjacent systems, such as blood vessels, of which it is a part. As with the other steps of the operation, this step takes great care to perform.