Diverticulosis - Risk Factors

Risk Factors

1. increasing age
2. constipation
3. a diet that is low in dietary fiber (contradicted by the latest study)
4. high intake of meat and red meat
5. connective tissue disorders (such as Marfan syndrome and Ehlers Danlos Syndrome) that may cause weakness in the colon wall
6. hereditary or genetic predisposition

The exact etiology of colonic diverticulosis has yet to be fully clarified and many of the claims are only anecdotal. The modern emphasis on the value of fiber in the diet began with Cleave. A strong case was made by Neil Painter and Adam Smith that a deficiency of dietary fiber is the cause of diverticular disease. They argued that the colonic muscles needed to contract strongly in order to transmit and expel the small stool associated with a fiber deficient diet. The increased pressure within the segmented section of bowel over years gave rise to herniation at the vulnerable point where blood vessels enter the colonic wall.

Denis Burkitt had suggested that the mechanical properties of the colon may be different in the African and the European subjects. He theorized that because Africans eat a diet containing more fiber than Europeans and use the natural squatting position for defecation, they pass bulky stools, and hence rarely if ever develop colonic diverticulosis.

However, the U.S. National Institutes of Health (NIH) considers the fiber theory "unproven." Furthermore, a February, 2012, study in the journal Gastroenterology found that "A high-fiber diet and increased frequency of bowel movements are associated with greater, rather than lower, prevalence of diverticulosis." The study involved 2,104 participants, 30–80 years old, who underwent outpatient colonoscopies from 1998 to 2010 and were interviewed regarding diet and physical activity.

Change in the strength of the colonic wall with age may be an aetiological factor. Connective tissue is a significant contributor to the strength of the colonic wall. The mechanical properties of connective tissue depend on a wide variety of factors, the type of tissue and its age, the nature of the intramolecular and intermolecular covalent cross links and the quantity of the glycosaminoglycans associated with the collagen fibrils. The submucosa of the colon is composed almost entirely of collagen, both type I and type III. Several layers of collagen fibres make up the submucosa of the human colon. The collagen fibril diameters and fibril counts are different between the left and right colon and change with age and in colonic diverticulosis,. The implication being that changes which are normally associated with ageing are more pronounced in colonic diverticulosis. Iwasaki found that the tensile strength of the Japanese colon obtained at postmortem declined with age. Similarly the mechanical properties of the colon are stronger in African than European subjects. However, this race-based claim is contradicted by the virtually identical incidence of diverticular disease in black and white Americans.

The strength of the colon decreases with age in all parts of the colon, except the ascending colon. The fall in tensile strength with age is due to a decrease in the integrity of connective tissue. Cross linkage of collagen is increased in colonic diverticulosis. The mucosal layer is possibly more elastic and it is likely that the stiffer external layers break and allow the elastic mucosa to herniate through forming a diverticulum. Collagen has intermolecular and intramolecular cross links which stabilise and give strength to the tissue in which it is located. Accumulation of covalently linked sugar molecules and related increasing cross linking products are found in a variety of tissues with ageing, skin, vascular tissue, the cordae tendinae of heart valves and the colon. This reduces the strength and pliability of the collagen. Colonic diverticulosis increases in frequency with age. There is a reduction in the strength of the colonic mucosa with age, and that increased contractions in the descending and sigmoid colon secondary to an insufficient fibre content of the diet cause protrusion through this weakened wall. Colonic diverticulosis is in general a benign condition of the bowel which uncommonly becomes symptomatic and even less commonly becomes a truly clinical complicated problem.