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Diverticula are out-pouchings or herniations in the wall of the esophagus, small, or large intestine. They may be either congenital or acquired. The majority of this discussion will center on diverticula of the small and large intestine, as these are the type most commonly encountered in clinical practice. Congenital diverticula are herniations of the entire thickness of the intestinal wall, while the more common acquired diverticula consist of herniations of the mucosa through the muscularis, generally at the site of a nutrient artery.(1)
The most common location for diverticula in the small intestine, with the exception of Meckel's diverticulum, is in the jejunum or duodenum. Most frequently, diverticula are asymptomatic and are often discovered incidentally upon upper gastrointestinal x-rays. Symptoms occur because of their anatomic proximity to other structures, or when inflammation or bleeding occurs.
Duodenal diverticula occur most generally, singly, and arise from the medial surface of the second portion of the duodenum. While in most patients they cause no symptoms, they may rarely cause the symptoms associated with acute diverticulitis, and extremely rarely they may perforate. Periampullary diverticula are sometimes associated with cholangitis or pancreatitis. Jejunal diverticula are even less common, but may also be the site of acute inflammation, bleeding, or perforation.
A patient with multiple jejunal diverticula may have a malabsorption that occurs as a result of bacterial overgrowth within the diverticula. Such bacterial overgrowth results in mucosal damage, deconjugation of bile salts, and a vitamin B12 malabsorption. This bacterial overgrowth and malabsorption is also seen in other clinical situations where intestinal stasis occurs.
Meckel's diverticulum is a congenital abnormality of the digestive tract. The diverticular sac may be lined with normal (ileal) mucosa, gastric mucosa, or colonic mucosa and may produce hemorrhage, inflammation, or obstruction in children and teenagers; however, they are rarely symptomatic after age five.
Colonic diverticula occur most frequently in the sigmoid colon, and with lesser frequency in the proximal colon. In western populations, the occurrence increases with increase in age, and in patients over 50, the incidence is 20-50 percent. While the exact mechanism is unknown, it is thought to involve increased pressure in the lumen of the intestine. An increase or thickening in the muscle coat of the colon found in most patients with colonic diverticula suggests that herniations in the mucosa are caused by the increased pressure of muscle contractions.
Since colonic diverticula are rare in underdeveloped nations, it has been postulated that the formation may be due at least in part to highly refined western diets, which generally lack in dietary fiber or roughage. In such diets, the feces contain less bulk, which causes the colon to narrow and requires an increased pressure to move the smaller fecal mass. As with small intestinal diverticula, they are primarily asymptomatic and are often found incidentally during colonoscopy or barium enema.
The major consequences are acute and chronic inflammation, and hemorrhage, but these only occur in a small percentage of patients with diverticulosis. It is therefore important to avoid the temptation of attributing bleeding and abdominal pain to diverticulitis, particularly in the elderly patient, until other causes such as colonic neoplasm have been excluded.
Diverticulitis can be defined as inflammation that occurs in or around the diverticular sac. The cause of diverticulitis is probably mechanical, related to the retention of undigested food residues and bacteria, which may form a hard mass called a fecalith.(1) This compromises blood supply to the thin-walled sac and makes it more susceptible to invasion by colonic bacteria. Diverticulitis occurs more often in men than<
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