After the blood supply to the region of the appendix and the right colon has been divided, the terminal ileum may be further mobilized. An incision is made into the mesentery of the terminal ileum with a clear view of the ureter at all times to avoid its injury. It is often necessary to remove a portion of the terminal ileum because of its possible involvement with the inflammatory process (Figure 9).
Considerable time is required to separate the blood supply proximally from the site where the ileum is to be divided. Several centimeters of ileum can be denuded of blood supply in preparation for the development of an ileostomy (Figure 9). The blood supply to this portion of the ileum should be divided very carefully, almost one vessel at a time, maintaining the large vascular arcade at some distance from the mesenteric border. A noncrushing vascular-type clamp is applied to the ileal side and a straight Kocher clamp to the cecal side in preparation for the division of the intestine (Figure 10). Most commonly, however, the ileum is divided with a cutting linear stapler (GIA) stapling instrument. The contents of the Kocher clamp can be ligated with heavy silk or absorbable suture to facilitate handling of the right colon (Figure 11).
The colon is then retracted medially, and the mesentery is divided up to the region of the middle colic vessel (Figure 12). Two half-length clamps should be applied proximally on the middle colic vessels because of their size and the increased vascularity in ulcerative colitis. The mesentery of the transverse colon is divided rather easily between pairs of clamps and the contents carefully ligated. This can be done at some distance from the inferior surface of the pancreas. As additional portions of colon are freed, they are incorporated in towels to avoid tearing the bowel wall and possible gross contamination.