Your bowel consists of 2 specialised parts, namely the colon and the rectum. The colon is broadly referred to as having 2 halves, the right colon (or right hemicolon) and the left colon (or left hemicolon). The rectum is broadly divided into three parts, the upper, middle and lower thirds. Various parts of the colon have specific names, as shown in the diagram below. Doctors refer to parts of the bowel sometimes according to whether it is the upstream portion ("proximal") or the downstream portion ("distal"). The colon is very variable in its length and in the number of convolutions or bends in the tubing.
What is Diverticular Disease?
Your colon consists of a muscular tube and an inner tube called the mucosa. Throughout its course, blood vessels must penetrate through the muscular coat to norish the mucosal layer. Where they do so, the wall is weaker and in diverticular disease the mucosa bulges through the muscular coat to form litttle pockets or blisters in the colon tube. Diverticulum means "pouch" or "pocket" in Latin. You may have one diverticulum, or many diverticula. A simple analogy is that of a worn bicycle tyre, with the inner tube blistering through the rubber where the rubber has worn thin.
Normal colon tubing Diverticular colon tubing
Perhaps the correct term for this condition is diverticulosis, since diverticular disease conjures up images of an illness. In fact most people in the West will eventually develop some diverticula, and most are completely untroubled by it, so it is hardly a disease for the majority of us. Between one-third and a half of the population of Western Europe and North America will get diverticula in the colon during their lifetime. The likelihood of having the condition increases as we get older. Less than one person in 20 has the condition before the age of 40, rising to a quarter of us by 60 years of age and two-thirds by the age of 85. When diverticulosis does produce symptoms, we refer to it as Diverticular Disease.
What causes it?
Our highly refined Western diet, compared to that diet of people who live in developing countries, is probably to blame. We simply don't eat enough fibre in our diets and fibre bulks up the stool and binds water to itself. Narrower stools are harder to grip when the muscles of the colon contract to move it along (think of squeezing the meat of a sausage along the sausage after you have taken some of the meat out of the tube). The colon must squeeze harder and the harder the squeeze, the higher the pressure - and the higher the pressure in the colon, the more the mucosa will be forced out through the points of least resistance in the muscular tube.
Can it be prevented?
An increase in the proportion of fruit, vegetables and cereals in the diet may do so, but this would need to be a life-long eating behaviour to have any impact. Our uncivilised ancestors would release flatus and defaecate whenever the need arose unlike we do now, preferring to postpone the act until a more suitable opportunity was found. Some believe that this prolongation of the time we hold on to flatus and stool leads to drying out of the stool and increased pressure in the system, potentiating the effects of our refined diet.
What are the symptoms of diverticular disease?
Diverticular Disease: persistent abdominal pain, often low down in the left side of the abdomen, together with bloating and an irregular bowel habit are the commonest symptoms. The bowels may be unaffected in their pattern, or they may vary from looseness to constipation. Very occasionally patients exerience quite substantial haemorrhage in the bowel content.
Diverticulitis: This is characterised by severe lower abdominal pain, bloating, often loose stool or conversely even bowels not working, tenderness and general symptoms of poor health such as a lack of appetite, nausea or a temperature. Bloody diarrhoea is not uncommon. Such patients are usually treated initially in primary care wth antibiotics (if the attack is mild) but some require admission to hospital as an emergency. In severe cases, the colon may become so inflamed as to develop inflammation around it, even with abscesses. This can be graded in severity by a CT scan.
Stricture: After repeated cycles of inflammation and then subsequent healing, the colon may become scarred and deformed. This can produce a narrowing in the calibre of the colon tube, called a stricture. Strictures impede the passage of stools, causing more pain and blockages characterised by bloating, cramping and nausea.
Perforation: very occasionally a diverticulum may burst. If is bursts gradually, the body may partially seal off this perforation and create an abscess cavity near the colon. If the diverticulum perforates freely, gas and faeces containing bacteria will leak into the abdominal cavity and cause peritonitis. This will be rapidly fatal if not attended to by operative surgery in hospital.
How is the diagnosis of diverticular disease made?
This condition is established by obtaining a careful history of your symptoms and by clinical examination. Confirmation of the problem usually comes from either directly inspecting the colon, or by obtaining images of it through radiological means. Direct inspection is by a camera inserted part of the way through the colon after an enema is administered (this procedure is called a flexible sigmoidoscopy) or alternaively the camera can be inserted through the full length of the colon after a cleansing of the colon (a procedure called a colonoscopy). Indirect radiological procedures are either a barium enema X-ray (requiring bowel cleansing), a plain CT scan (without cleansing) or a CT colonography scan (a CT with cleansing).
What should you eat?
Try to eat a mixture of high fibre foods. Fruit, vegetables, nuts, wholemeal bread and pasta, wholegrain cereals and brown rice are all good sources of fibre. Aim to have at least one high fibre food with each meal and try to have five portions of fruit or vegetables each day. Drink at least two litres (8 to 10 cups) of fluid every day.
People with symptoms from diverticular disease respond differently to fibre in the diet. One person may be helped by increasing the amount of plant fibre in the diet, another may feel that their symptoms become worse. The type of fibre one eats may usefully be varied. Some people find that it helps to take fibre in the form of fruit and vegetables (soluble fibre) rather than that in cereals and grains (insoluble). This is because insoluble fibre may cause more bloating and pain. Bran aggravates symptoms for some people and is not routinely recommended. It is not possible to make rules about diets which suit everyone - an element of trial and error in what we eat is often helpful in finding what fibre suits us best, so keep a food diary of what you consume and the symptoms that occurred later that day or the next. If required, a dietician may be engaged in your care to advise you on your diet and to help you find a better dietary intake.