Diverticular disease is a twentieth century disease that results in part from changes in diet, age and lifestyle although there is little research to support this (Bassotti et al., 2003). It is one of the most frequent diseases seen in gastroenterology departments.
Diverticula are small herniations in the bowel wall; they can occur anywhere in the bowel. The diverticular pouches usually appear in the descending and sigmoid colon (Stollman and Rashkin, 1999), frequently manifesting at the weakest point in the colonic wall where the blood vessels supply the mucosa in the circular muscle layer. A diverticulum is an outpouching of the mucosa of the lining of the bowel. Diverticulosis is the name give to this manifestation and most patients with these diverticula will not have any symptoms. The symptoms of diverticular disease in westernised countries usually relate to the sigmoid colon. Right-sided diverticular disease is more prevalent in the eastern countries of the world. In countries where the diet is high in fibre and very low in refined carbohydrates, diverticular disease is virtually unknown (Hyde, 2003).
The outpouches are blind ends within the bowel wall where undigested food particles, faecal matter and debris can collect and become trapped; this can lead to inflammation and then to diverticulitis. The diverticular pouches usually appear in the descending and sigmoid colon; they can be a single diverticulum or in abundance. Sigmoid diverticular disease is common in the western world and thought to be caused by lack of fibre (Painter and Burkitt, 1975) and over-refined carbohydrates and flour (Keighley and Williams, 1997) in the diet.
Changes in lifestyle and eating patterns in the latter half of the twentieth century are thought to have contributed to the increase in diverticular disease. Another cause of diverticular disease is a consequence of high intraluminal pressure in the bowel, together with slow transit times of the stool. Stollman and Rashkin (1999) say that:
High intraluminal pressure is caused by segmental contractions of the circular muscles and by contractions of the colonic wall between these segments.
Slow transit time of the stool is the time that the faecal matter takes to navigate the colon. This can assist the formation of the diverticula, which under pressure bulge at their weakest points. Fibre helps to speed this process but, as already stated, the diet is now lacking adequate amounts of fibre to accomplish this. The faecal matter stays in the colon for longer periods of time and becomes more constipated as a result, causing more pressure and straining on evacuation of the bowels.
All of these activities can result in the formation of a diverticulum at the weakest point in the circular muscle layer, where the blood vessels supply the mucosa (Bassotti et al., 2003). The lumen of the colon is at its narrowest in the sigmoid colon and therefore comes under vast intraluminal pressure; together with slow transit time of the stool through the colon (Mimura et al., 2002), this causes pressure that is exerted on the bowel wall, causing herniations at the weakest point.
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