A colonoscopy is a procedure carried out to examine the inside of the large intestine (colon and rectum). A flexible viewing tube with attached camera and light on the end called colonoscope is used to screen the inner lining (mucosa) of colon and rectum. The tube is inserted through the anus, gradually allowing it to pass through the rectum and colon.
Meanwhile camera on the instrument relays a video image of the large intestine to a computer monitor allowing the doctor to carefully examine the intestinal lining. The tube is slowly pulled out once the scope reaches the entrance of the small intestine.
Why is colonoscopy done?
Colonoscopies are most often conducted to detect colon cancer or colorectal cancer. They are also advised when patient exhibits the following symptoms:
The test is also conducted as a routine screening method if any individual has a family history of colon cancer or has had polyps earlier.
Before going through the colonoscopy, patient needs to totally clear out his/her digestive tract which is known as bowel preparation as colon devoid of any solid content provides a clear view. Solids are absolutely avoided; he will be put on a clear liquid diet containing filtered fruit juice, water, plain coffee, plain tea, sports drinks such as Gatorade and gelatin.
If patient has any health issue and is on some medication, he should discuss this with the physician as some drugs may interfere with the examination.
Laxative preparation: Along with the liquid diet, patient is required to consume laxative solution before the procedure, to cleanse the colon. There is many a solution available in the market and each one has its own set of advantages and disadvantages. Most of them contain an active ingredient called polyethylene glycol (PEG) which helps in flushing out the fecal matter.
The most common solutions available with PEG are Golytely, Colyte and NuLytely. These preparations are available in the form of powder which is mixed in almost a gallon of clear water (according to the instructions given on the packet) and it is ready to consume. Usually patient is asked to take 8 oz glass of the mixture every 10 minutes until the entire gallon is finished.
Fleet's Phospho-soda is also a powder taken with water but unlike PEG preparation it requires less water and patient is spared from consuming huge amounts of water. One should hydrate oneself enough after drinking the solution. This preparation leads to bowel movement anywhere from 30 minutes to 6 hours after it is taken.
These preparations may have side effects like cramping, nausea and under very rare circumstances may lead to kidney damage. In addition to laxatives, physician may recommend an enema to clear out the last few inches of the colon
Typically colonoscopy takes about 30 to 40 minutes. Patient is usually mildly sedated and will be asked to lie down on his left side pulling his legs towards the chest. Doctor will insert the colonoscopic tube through anus and guides it through the colon. The scope enlarges the colon with carbon dioxide gas to give the doctor a clear view.
Tube is withdrawn once it reaches the small intestine and the lining of the large intestine is carefully observed again. Colonoscopy in addition to examining the colon also removes any polyps or growths found and if required, collects the tissue samples (biopsies) with specific attachments.
What are the risks involved
Usually colonoscopy does not give rise to any complications, but under rare conditions biopsy may result in slight bleeding. Another rarest of complication could be a tear on the bowel wall, for which surgery is the only solution. Sedatives may cause nausea, allergy or other side effects which may go away eventually.
But if patient notices any of the symptoms like large amounts of bleeding, the passage of clots, or severe abdominal pain, it should be immediately reported to the doctor
Alternatives to colonoscopy
There are some other tests available as an alternative to or in addition to colonoscopy.
Sigmoidoscopy test is almost similar to colonoscopy which also makes use of flexible tube to view a part of the colon. The scope of the test is limited as the tube used is shorter and does not cover the entire colon.
Barium enema is a test where in a liquid called barium is inserted into the colon with the help of the tube and then x-ray images of abdomen are taken to detect the diseases of colon
Virtual colonoscopy is one of the most popular alternatives to colonoscopy. This technique makes use of CT scan images of colon to detect the colon abnormalities. (Similar bowel preparation is needed though).
But virtual colonoscopy cannot detect the polyps smaller than 5mm in size and also cannot remove existing polyps. Hence this test is generally used as initial screening test prior to the regular colonoscopy.