The appendices epiploica lie along the entire colon from the cecum to the upper part of the rectum. Torsion or vascular thrombosis causes their infarction (Fig. 13.180), hemorrhage
into the fatty tissues, abscess, or stricture formation. Appendices epiploica may also autoamputate and lie freely in the peritoneal cavity, where they may calcify and turn into “peritoneal mice” (Fig. 13.181). Histologically, they consist of fat that may appear infarcted and completely surrounded by a dense fibrous capsule or may show variable degrees of fat necrosis and calcification, again surrounded by fibrous material.

Irritable bowel syndrome is the most common gastrointestinal disorder encountered in general and gastroenterology practices (624,625). It is characterized by abdominal pain, altered bowel habits (diarrhea or constipation), bloating, or the passage of mucus per rectum. A number of criteria have been advanced to standardize the clinical diagnosis (626). The condition develops in women more often than men, often in those with underlying depression or anxiety. Subtle but nonspecific histopathologic changes can be found in patients with this diagnosis. These include increased numbers of mucosal lymphocytes, mast cells, endocrine cells, and nerve cells as summarized by Kirsch and Riddell (627).