The part of the large intestine that joins the small intestine is called the caecum. Directly above the anus is a short length of large intestine – 12-15cm long – called the rectum. The colon extends from caecum to the rectum and is divided into 4 parts: the ascending colon, which rises upwards from the caecum; the transverse colon, which runs across the body from right to left; the descending colon, which sweeps downwards; and a relatively short section called the sigmoid colon, which leads to the rectum.
A major function of the colon is to extract fluids from what remains of food after its nutrients have been absorbed in the small intestine. The colon also provides a temporary storage place for solid wastes, as well as a channel for their removal from the body. Colon cancer and rectal cancer, often referred to collectively as cancer of the bowel, is one the most common cancers of the digestive system. All parts of the large intestine can develop cancer although most cases of colon cancer occur in the descending colon, sigmoid colon and rectum.
The type of food you eat seems to increase or decrease your chances of getting colon cancer. A variety of studies suggest that people who consume large quantities of high-fat and low-fibre foods run a greater risk than those who eat a low-fat and high-fibre diet. Therefore, you can reduce your chances of getting colon cancer by, decreasing the amount of ‘bad’ foods you eat and, increase your intake of ‘good’ cancer preventing foods.
Among the ‘good’ cancer preventing foods are vegetables (especially broccoli, Brussels sprouts and cauliflower), whole grains and legumes (beans and peas). Your diet should also include sufficient amounts of vitamin A and C, which, according to experts help to neutralise cancer-causing substances in food. Diet is one aspect that can control the onset of colon cancer, however, there are factors that you may have no control over. For instance, an uncommon inherited tendency to develop many small to large growths in the colon. These growths, or polyps, look somewhat like mushrooms.
There are signs that may be heeded as to whether cancer of the colon or large intestine is present or a condition that may lead to it, may be present in the body. In general, any persistent change in bowel habits should alert you. Diarrhoea or constipation that will not go away after about a week, despite the use of medication; stools that are narrower than usual, which can occur if a growth is blocking or narrowing any part of the colon or rectum are not sure indicators of colon cancer, but may indicate a problem and the sooner you find out exactly what these changes mean, the better your chances will be in dealing with them.
One indication that you may have cancer of the colon may turn up when a routine test for invisible traces of blood in the faeces is positive. Bear in mind that many other conditions besides cancer can lead to the presence of small amounts of blood in the faeces; these conditions can include haemorrhoids (piles), non-cancerous tumours or infections. A routine physical examination by a doctor should be done even when no colon cancer is suspected. After a general inspection, he may refer you to a specialist who will use an instrument called a sigmoidscope to examine the rectum and lower part of the sigmoid colon in more detail. If a colon cancer growth is detected, the specialist, perhaps in collaboration with a surgeon, will outline a course of treatment. The choice of therapy will be based on the size of the growth, on how much of the colon is affected and whether the cancer has spread to other areas.
Like many other cancers, there are three basic ways in which colon cancer can be treated: with surgery, radiotherapy or with anticancer drugs, or with a combination of these three approaches. The treatment will depend on where the colon cancer is situated, on its size and on whether it has invaded the wall of the colon or areas beyond it.