The large intestine, also called the large bowel consists of two main parts, the colon and the rectum. The colon receives digestive waste from the small intestine and forms stool which is propelled towards the anus through a small segment called the rectum.
Colonoscopy is a diagnostic procedure to evaluate the inner lining of the colon and rectum. It is performed with a colonoscope - a long, flexible lighted tube with a camera. The colonoscope is inserted into the anus and passed through the rectum and colon. It allows your doctor to view the entire colon and rectum as well as the lower part of the small intestine.
Colonoscopy is recommended for people aged 50 and above with a normal risk of colorectal cancer. The test helps to diagnose tumours, ulcers, polyps and areas of inflammation or bleeding. It is also indicated to check for the cause of
- Rectal bleeding, dark stools or blood in the stool
- Chronic diarrhea
- Anaemia due to iron deficiency
- Altered bowel habits
- Follow up post removal of colonic polyps & bowel cancer resection
- Unexplained weight loss and belly pain
- FOBT positive stool test
- Inflammatory bowel disease
To prevent visual obstruction during a colonoscopy, your doctor will advise you to stop consuming solid foods and limit your intake to clear liquids one day before the exam. You must also avoid beverages containing red or purple dye. You may have to temporarily stop taking your blood thinners, diabetes or blood pressure medications and iron supplements. A bowel prep may be prescribed the night before the procedure to loosen stools and increase bowel movements. An enema may be administered a few hours before the procedure
During the procedure, you may be given pain medicines and a sedative to reduce discomfort and help you relax.
- You will lie on your side with your knees drawn towards your chest.
- The colonoscope is inserted into your anus and moved slowly through the colon. Air is inflated into the colon to provide a clear view of the colon’s lining.
- You may experience abdominal cramping or an urge to pass stool when the scope is in your colon.
- The complete length of your colon is examined and images captured and relayed to an external monitor.
- During the procedure tissue samples may be removed with forceps for biopsy and polyps may be snared.
- The scope is then pulled out of the anus and the area cleaned. Passing gas can help relieve the abdominal cramps.
The colonoscopy takes around 20-30 minutes or longer.
After the procedure, it will take an hour for the sedative to wear off but you will still require someone to drive you home. A normal diet with increased fluid intake is usually recommended. If a polyp has been removed, you may be placed on a special diet. You may experience a sensation of bloating which can be relieved by walking. It is normal to pass a small quantity of blood with the first bowel movement after the procedure. Consult your doctor if you experience abdominal pain, high fever or increased blood in the stools.
Risks and complications
Colonoscopy is usually a safe procedure but as with any procedure, certain complications can occur. These include:
- Bleeding after a biopsy or polyp removal
- Perforation in the intestinal wall
- Anaesthetic complications: Aspiration pneumonia, drug reaction, swelling at the site of cannula insertion