In cases of malignancy of the stomach, it is desirable to resect the greater omentum, because it allows for improved removal of lymph nodes along the greater curvature of the stomach and because of the possibility of metastatic implants in this structure. Removing the omentum is not difficult and can commonly be effected with less technical effort than dividing the gastrocolic ligament adjacent to the greater curvature of the stomach (see Chapter 26, figures 8 to 10). For this reason, some prefer to use this procedure rather routinely, regardless of the indication for subtotal gastrectomy. The transverse colon is brought out of the wound, and the omentum is held sharply upward by the operator and assistants (figure 1). Using scissors of the Metzenbaum type, dissection is started at the right side, adjacent to the posterior taenia of the colon. In many instances the peritoneal attachment can more easily be divided with a scalpel or electrocautery than with scissors. A thin and relatively avascular peritoneal layer can be seen, which can be rapidly divided (figures 1 to 3). Upward traction is maintained on the omentum as blunt gauze dissection is utilized to sweep the colon downward, freeing it from the omentum (figure 2). As the dissection progresses, a few small blood vessels in the region of the anterior taenia of the colon may require division and ligation. Finally, the thin, avascular peritoneal layer can be seen above the colon. This is incised, giving direct entrance into the lesser omental sac (figures 4 and 5). In the obese individual it may be easier to divide the attachments of the omentum to the lateral abdominal wall just below the spleen as a preliminary step. If the upper margin of the splenic flexure can be visualized clearly, the splenocolic ligament is divided and the lesser sac entered from the left side rather than from above the transverse colon, as shown in figure 6. The surgeon should be on guard constantly to avoid injuring the splenic capsule of the middle colic vessels, since the mesentery of the transverse colon may be intimately attached to the gastrocolic ligament, especially on the right side. As the dissection progresses toward the left, the gastrocolic omentum is divided, and the greater curvature of the stomach is separated from its blood supply to the desired level (figure 6). In some instances it may be easier to ligate the splenic artery and vein along the superior surface of the pancreas and remove the spleen, especially if there is a malignant growth in this location. It should be remembered that if the left gastric artery has been ligated proximal to its bifurcation, and the spleen has been removed, the blood supply to the stomach has been so compromised that the surgeon is committed to total gastrectomy.
In the presence of malignancy the omentum over the head of the pancreas is removed, as well as the subpyloric lymph nodes (figure 7). Small, curved clamps should be utilized as the wall of the duodenum is approached, and the middle colic vessels, which may be adherent to the gastrocolic ligament in this location, should be carefully visualized and avoided before the clamps are applied. Unless care is exercised, troublesome hemorrhage and a compromised blood supply to the colon may result.