Intestinal Surgery
Anatomy of the Small and Large Intestine
The intestines constitute the largest organ system within the abdominal cavity. Pelvic surgery always translates into some contact with the intestines. Although some individual variation may be noted, upon entering the peritoneal cavity of a person who has not previously been operated on, the greater omentum can be seen to cover the intestines (Fig. 93–1A). The omentum takes its origin from the greater curvature of the stomach and also attaches to the transverse colon (Fig. 93–1B). Beneath the omentum lies the small intestine (Fig. 93–2A). The small bowel measures 22½ feet in length, and for the most part is completely covered with peritoneum and is suspended by a wide mesentery (Fig. 93–2B). The latter extends from the upper left abdomen to the lower right portion of the posterior wall of the abdomen (Fig. 93–3). The small intestine is divided into three portions: (1) duodenum, which is uncommonly related to gynecologic surgery; (2) jejunum; and (3) ileum; all three are frequently encountered (Fig. 93–4). The duodenal–jejunal junction is secured by a fibromuscular band on the upper left side of the abdomen. This band is called the ligament of Treitz. This is a convenient initial landmark for systematic examination of the entire small intestine for a suspected injury (Fig. 93–5A through C). Another important anatomic reference point is the ileocecal junction, where a valve connects the small to the large intestine (Fig. 93–6A, B). The small intestine receives its blood supply from the superior mesenteric artery via its mesentery (Fig. 93–7). The vessel branches into a series of arches, which terminate in a small straight artery that surrounds the segment of intestinal wall. The nerve supply emanates from the superior mesenteric plexus of nerves, which is in direct continuity with the celiac plexus.
The large bowel measures approximately 5 feet in length and can be distinguished from the small intestine by the presence of appendices epiploicae (three longitudinal bands of muscle fibers) and by its larger diameter (Fig. 93–8A). The large intestine forms a three-sided framelike structure (see Figs. 93–2B, 93–8B). On the right side, the cecum frequently dips into the pelvis and importantly terminates in the vermiform appendix. The ascending colon at its hepatic flexure imperceptively joins the transverse colon. The latter is located just beneath (inferior to) the stomach and connects to the left, or descending, colon at the splenic flexure.
The left (descending) colon joins the S-shaped sigmoid portion in the left iliac fossa. The sigmoid colon enters the pelvis by passing anterior to the sacrum and crossing it from the left to right side of the pelvis (Fig. 93–9
