What causes colonic diverticula?
Most diverticula occur in the left colon; they also occur elsewhere, but not in the rectum. The common hypothesis is that relatively high pressures generated within the colon by muscular contractions force the inner mucosa to penetrate through the path of small blood vessels within the colon wall and to bulge beyond the serosa (Figure 1). The muscle layer along the site of left colon diverticula is commonly thickened, lending credibility to the notion of high intracolonic pressure. The result may be rows of bulges along the colon at the sites of the penetrating arteries.
Why such this may occur in one-half the North American and European populations and not the other half is a mystery. Perhaps the great prevalence in Western populations is related to the relative lack of dietary fiber consumed by these populations. Low dietary fiber results in small stools, and an undistended colon may generate more pressure within the colon. Whatever the cause, the presence of colonic diverticula – often discovered during the course of a barium enema x-ray, colonoscopy, or surgery – is almost always of no significance.
Do diverticula cause symptoms?
Most individuals who possess colonic diverticula are unaware of them. The condition of having colonic diverticula is called diverticulosis. Indeed, the usual method of discovery of diverticula is by chance.
There is no evidence that the diverticula themselves cause any symptoms. It is hard to imagine how one could be aware of a few outpouchings in the large intestine. The myth that abdominal pain may be caused by diverticular disease is explained by coexisting painful conditions such as irritable bowel syndrome (IBS). If diverticula occur in about one-half of the population over age 60 and IBS occurs in 15% of adults, it is not surprising that sometimes they may coexist. One does not lead to the other.