Colonoscopy is the endoscopic examination of the large bowel and the distal part of the small bowel with a fiber optic camera on a flexible tube passed through the anus. It may provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or removal of suspected lesions. Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not.
A colonoscopy allows an examination of the entire colon (measuring four to five feet in length).
The colon must be free of solid matter for the test to be performed properly. For one to three days, the patient is required to follow a low fiber or clear-liquid only diet. Examples of clear fluids are apple juice, chicken and/or beef broth or bouillon, lemon-lime soda, lemonade, sports drink, and water. It is very important that the patient remain hydrated. Sports drinks contain electrolytes which are depleted during the purging of the bowel. Orange juice, and milk containing fiber should not be consumed, nor should liquids dyed red, purple, orange, or sometimes brown; however, cola is allowed. In most cases, tea (no milk) or black coffee (no milk) are allowed.
The day before the colonoscopy, the patient is given a laxative preparation in the form of Moviprep and large quantities of fluid
Since the goal of the preparation is to clear the colon of solid matter, the patient should plan to spend the day at home in comfortable surroundings with ready access to toilet facilities.
The patient may be asked to stop aspirin for up to ten days before the procedure to avoid the risk of bleeding if a polypectomy or biopsy is performed during the procedure.
During the procedure the patient is given sedation intravenously.
The endoscope is then passed through the anus up the rectum, the colon (sigmoid, descending, transverse and ascending colon, the ceacum), and ultimately the terminal ileum. The endoscope has a movable tip and multiple channels for instrumentation, air, suction and light. The bowel is occasionally insufflated with air to maximize visibility Biopsies are frequently taken for histology.
Suspicious lesions may be cauterized, treated with laser light or cut with an electric wire for purposes of biopsy or complete removal -polypectomy. On average, the procedure takes 20–30 minutes, depending on the indication and findings.
After the procedure, some recovery time is usually allowed to let the sedative wear off. You should not drive following the sedaton for 24 hours and will need to have a person with you to help you home afterwards (again, depending on the sedation method used).
One very common aftereffect from the procedure is a bout of flatulence and minor wind pain caused by air insufflation into the colon during the procedure.
An advantage of colonoscopy over x-ray imaging or other, less invasive tests, is the ability to perform therapeutic interventions during the test. A polyp is a growth of excess of tissue that can develop into cancer. If a polyp is found, for example, it can be removed by one of several techniques. A snare device can be placed around a polyp for removal. Even if the polyp is flat on the surface it can often be removed.
This procedure has a low (0.35%) risk of serious complications.