What is the large bowel?
The large bowel is part of the gastrointestinal tract, which extends from mouth to anus. The gastrointestinal tract digests your food and gets rid of the waste. The large bowel is involved with the disposal of waste products from the body. It's also called the intestine or gut.
The large bowel is about 140cm (5 feet) long. It starts in the right side of your abdomen, where it is called the caecum. It runs in a large loop round the abdomen and down into the pelvis as the colon. The lowest part of the large bowel is called the rectum, which opens at the anus. Above the rectum, the bowel is S shaped and is called the sigmoid colon (sigma is the Greek name for the letter S). During a sigmoidoscopy, only the last one to two feet of the bowel is examined.
What has gone wrong?
There are many conditions that can happen in the lower large bowel, including:
- Irritable bowel syndrome - One of the most common causes of large bowel symptoms is irritable bowel syndrome (IBS). Here, the bowel muscle loses its smooth, peristalsis action and goes into cramps. This can cause pain, swelling of the abdomen, diarrhoea and a discharge of mucus.
- Haemorrhoids - Haemorrhoids, also called piles, are common. They are enlarged and engorged blood vessels in or around the anus. They may cause pain, bleeding and itching.
- Inflammatory bowel disease (IBD) - This is an inflammation of the lining of the bowel, also called colitis.
- Polyps - These are lumps on the inside of the bowel and can cause bleeding. Polyps are best removed because, even though they are not cancer, they can become cancerous over time. A sigmoidoscopy is sometimes used to check that more polyps have not formed in patients who have had polyps removed in the past.
- Cancer - There may be a tumour or cancer. Most people who have a sigmoidoscopy do not have cancer. Sigmoidoscopies are also used to check the bowel in patients who had previous treatment for bowel cancer or a family history.
With piles being so common, there is a chance of another cause for your bowel symptoms. You need to have the lowest part of your large bowel examined to rule out these other conditions.
A sigmoidoscopy is also used to check the bowel after other operations. If you have been treated for a split in the back passage, called an anal fissure, a sigmoidoscopy may be done to check there is no other condition present.
We may also use as sigmoidoscopy to examine the healing of a join, called an anastomosis, in the lower large bowel, after a bowel operation.
You should ask your doctor to explain why he feels you need a sigmoidoscopy.
The aim of the examination is to find out what is happening in the lower bowel to cause the symptoms you have. This means that the correct treatment can be given for your condition.
The sigmoidoscopy gives a direct view of the lining of the large bowel, compared with just shadows as seen on a barium enema x-ray. It is a quick and safe of examining the lowest part of the large bowel. A general anaesthetic is not usually needed for this procedure.
During the sigmoidoscopy we can take small samples of the bowel lining, called biopsies, for examination under the microscope. We can also remove polyps, if any are found. A narrowing of the lower bowel, called a stricture, can be stretched.
Are there any alternatives?
You will probably have a series of tests to find out what is causing your symptoms. For example, you may have a barium enema. A liquid that shows up on x-rays, called barium sulphate, is passed into the bowel through the anus. A series of x-rays are taken from different angles to show up as much of the bowel as possible.
If the barium enema showed you had a polyp, you may then have a sigmoidoscopy to have it removed.
If the sigmoidoscopy is normal, but you still have bowel symptoms, we may need to check the bowel further up, using more complex tests such as a colonoscopy. The endoscope used here is longer and is able to examine the whole of the large bowel, around to the caecum and appendix.
There is another type of sigmoidoscopy, called a rigid sigmoidoscopy. This can used to view up to 25cm (10 inches) of the bowel, into the rectum, which is fairly straight compared with the S shaped sigmoid colon higher up. A rigid sigmoidoscope will usually give a good view without any treatment to clear the bowel. A flexible sigmoidoscope is needed to pass round the sigmoid colon. The bowel usually has to be cleaned out before a flexible sigmoidoscopy.
There are tests of your stools that can be done to check for bleeding, such as the faecal occult blood test.
What if you do nothing?
If you have symptoms, such as blood in your stools, they should be investigated, as leaving things as they are can be very risky. You may be missing out on important treatment.
Author: Mr Michael Edwards FRCSEng FRCSEd. Consultant general surgeon.
© Dumas Ltd 2006