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Diverticulosis
Diverticular Disease of the Colon
Diverticulosis of the colon is an acquired condition that results from herniation of the mucosa through defects in the muscle coats ( Fig. 90.1 ). Defects are usually located where the blood vessels pierce the muscular wall to gain access to the submucosal plane. These vessels enter at a constant position, just on the mesenteric side of the two lateral taeniae coli, so diverticula typically occur in two parallel rows along the bowel. Appendices epiploicae (omentales) are also situated in this part of the circumference.
Diverticula probably arise from pulsion as a result of increased intraluminal pressure from uncoordinated peristalsis or inadequate luminal contents, possibly resulting from a low-fiber diet. Diverticula do not occur in the rectum but may be found throughout the entire colon. They are more common in the left side and usually affect the sigmoid colon. Diverticula are relatively rare in persons younger than 40 years of age but are common (60%) in persons older than 60 living in Western countries. The incidence is dramatically higher in Western countries, where the diet is much lower in fiber; this decreased fiber intake results in decreased colonic luminal content, and pressure from wall contraction is transmitted to the wall rather than to the luminal content. Therefore the formation of diverticula is related to fiber deficiency. The fact that contractions and their force are greatest in the sigmoid supports the theory that diverticula are more prominent in the sigmoid than in the rest of the bowel. Associated with chronic diverticula formation is the gradually increased deposition of connective tissue by elastin, resulting in thickening of the sigmoid, with some bowel rigidity where large amounts of elastin are deposited.
Although diverticula may form in the second or third decade of life, they are usually asymptomatic at that time.
Clinical Picture
If discovered during a barium enema examination, computed tomography (CT) scan, or colonoscopy performed for other clinical reasons (e.g., gastrointestinal [GI] bleeding, irritable bowel syndrome [IBS]), diverticula are assumed to be asymptomatic. Approximately 60% of the Western population older than 80 years of age have significant but asymptomatic diverticula formation. Furthermore, the high percentage of patients with IBS often includes those who have some diverticula formation, but not diverticulitis (see Chapter 90).
Many physicians assume that the diverticula are not causing symptoms when in reality they may cause mild symptoms. In addition, many patients with diverticula have symptoms but do not develop acute or chronic diverticulitis. Some may report a low-grade, dull ache in the left lower quadrant or a change in bowel habit. Some thought to have IBS may have diarrhea or constipation. However, diverticula are rarely thought to cause such symptoms unless temperature and white blood cell (WBC) count are elevated or imaging findings demonstrate spasm in the area of the diverticula.
On the basis of its natural history, diverticular disease is now classified into asymptomatic, symptomatic uncomplicated, and complicated types.
Diagnosis
The diagnosis of diverticula formation is made through barium enema examination, CT, or colonoscopy. When diverticula are discovered incidentally, no further diagnostic evaluation is needed. However, if the diverticula are accompanied by symptoms and the discovery was made during a barium enema or CT study, colonoscopy may be necessary. It may also be necessary to perform a WBC count and to monitor the patient carefully to identify any associated inflammation.
Treatment and Management
Most clinicians do not treat diverticula when they are discovered incidentally. Diverticula can result from a low-fiber diet, so all patients with diverticula should be advised to increase their fiber intake to 25 to 35 g daily (see Chapter 188 ). There is no evidence that increased fiber intake will reverse the formation of diverticula, but increased intake should prevent further progression and increased fiber in the bowel should decrease the pressure on the bowel wall.
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