If part of the inner lining of the intestine protrudes through the muscular coat on the outside of the intestine it is known as diverticulum, forming a small out pouching with a narrow neck. The lower part of the colon on the left side is the most common area for diverticula to occur and if there are several present the condition is called diverticulosis.

Is the cause of diverticula known?

The small intestine is the commonest place for a diverticulum to naturally occur. As people get older the number of diverticula increases as later life is the commonest time for these to occur. Diverticula in the large intestine occur in more than half the people over 70 in Britain while in the world’s rural areas, especially Africa, diverticula occur rarely. It is not known why other areas differ from western countries in this condition but diet may be important as the colon is the processor of dietary fibre present in poorly digestible plant foods.

In the west we eat less fibre than in other, primarily vegetarian, regions of the world. If the colon has plenty of fibre to deal with, the bulky soft contents keep the walls of the bowel apart. If little fibre is present, the stools tend to be smaller and harder, and they do not keep the walls of the tube-like colon apart when the muscles in the wall of the colon contract. These contractions form a ring-like narrowing to mix and push the contents along. Closed segments occur within which pressure is high and it is thought that this pressure pushes out the pouches.

Are diverticula risky or harmful?

We do not generally worry about our appendix which is a type of diverticulum. Diverticula are a common feature of many people’s colons, projecting from the colon walls but not becoming troublesome. As with appendicitis where the appendix becomes inflamed or infected, diverticula can be subject to infection also and this can present as pain in the affected region, a feeling of illness and the danger of the diverticulum perforating or bleeding. If the diverticula become inflamed then the resulting condition is known as diverticulitis.

What is diverticular disease?

There is normal thickness and appearance of the intestinal musculature in most people who have diverticula, but some can have thicker and microscopically abnormal structure in this muscle. Muscle thickening makes the colon narrower and makes its outline more irregular. The changes in the muscle which occur do not have a clear cause but infection may not be the cause and diet may well be irrelevant. Even if very few or no diverticula are present in the colon this abnormality of the muscle can occur. Diverticular disease is the name given to the combination of diverticula and abnormal muscle. The word disease is used because the works diverticula and diverticular sound very similar.

Diverticular disease presentation

The symptoms of diverticular disease include an irregularity of bowel habit with pellet like stool, bowel actions with blood passed with them, wind and bloating and pain in the abdomen down the lower left side. Irritable bowel syndrome has similar symptoms to diverticular disease perhaps secondary to both problems involving functional muscle abnormality.

The role of investigations

Diverticula are not generally discovered on their own but secondarily when investigation for other conditions is occurring, such as x-ray or endoscopy for abdominal pain or rectal bleeding. As healthy older people very commonly have diverticula the doctor has to be certain they are the cause of symptoms and not just incidental. If there is blood test evidence of inflammation somewhere in the body and the area of the diverticula is tender then a diagnosis of diverticulitis is possible. If the lower left sigmoid colon has increased folding of its lining this is the muscular abnormality of diverticular disease.

Giving information

Reassurance that a more serious disorder is not present helps people not to worry about the symptoms. An explanation of the difference between symptoms due to infection and those due to abnormal contraction of the muscle, without inflammation, helps people understand why one treatment may be advised and not another.