SPECIAL TYPES OF MECHANICAL INTESTINAL OBSTRUCTION

SPECIAL TYPES OF MECHANICAL INTESTINAL OBSTRUCTION Internal hernia

• Internal herniation occurs when a portion of the small intes - tine becomes entrapped in one of the retroperitoneal fossae or in a congenital mesenteric defect. The following are potential sites of internal herniation (all are very rare): - /uni25CF the foramen of Winslow; - /uni25CF a defect in the mesentery; /uni25CF a defect in the transverse mesocolon; /uni25CF defects in the broad ligament; /uni25CF congenital or acquired diaphragmatic hernia; /uni25CF duodenal retroperitoneal fossae; /uni25CF caecal/appendiceal retroperitoneal fossae; /uni25CF intersigmoid fossa. Internal herniation in the absence of adhesions is rare and a preoperative diagnosis is unusual. The standard treatment of an obstructed hernia is to release the constricting agent by division. This should not be undertaken in cases of hernia - tion inv olving the foramen of Winslow , mesenteric defects and - paraduodenal/duodenojejunal fossae as major blood vessels run in the edge of the constriction ring. The distended loop in such circumstances must first be decompressed (minimising contamination) and then reduced.

(b) Figure 78.3 Obstructing stricture of the distal descending colon in the presence of (a) a competent ileocaecal valve, resulting in gross caecal distension, and (b) an incompetent ileocaecal valve, allowing decom pression into the distal small bowel without gross caecal distension.