is the
Endoscopic examination of the large
Colon and the distal part of the
Small Bowel with a
CCD Camera or a
Fiber Optic camera on a flexible tube passed through the
Anus . It may provide a visual diagnosis (e.g.
Ulceration ,
Polyp s) and grants the opportunity for
Biopsy or removal of suspected lesions.
Virtual Colonoscopy , which uses 2D and 3D imagery reconstructed from
Computed Tomography (CT) scans or from
Nuclear Magnetic Resonance (MR) scans, is also possible, as a totally
Non-invasive medical test, although it is not standard and still under investigation regarding its diagnostic abilities. Furthermore, virtual colonoscopy does not allow for therapeutic maneuvers such as polyp/tumor removal or biopsy nor visualization of lesions smaller than 5 millimeters. If a growth or polyp is detected using CT colonography, a standard colonoscopy would still need to be performed. Colonoscopy can remove polyps smaller than one millimeter. Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not. Colonoscopy is similar but not the same as
Sigmoidoscopy . The difference between colonoscopy and sigmoidoscopy is related to which parts of the colon each can examine. Sigmoidoscopy allows doctors to view only the final two feet of the colon, while colonoscopy allows an examination of the entire colon, which measures four to five feet in length. Often a sigmoidoscopy is used as a screening procedure for a full colonoscopy.
Indications for colonoscopy include
Gastrointestinal Hemorrhage , unexplained changes in bowel habit or suspicion of
Malignancy . Colonoscopies are often used to diagnose
Colon Cancer , but are also frequently used to diagnose
Inflammatory Bowel Disease . In older patients (sometimes even younger ones) an unexplained drop in
Hematocrit (one sign of
Anemia ) is an indication to do a colonoscopy, usually along with an
EGD (esophagoastroduodenoscopy), even if no obvious blood has been seen in the stool (
Feces ).
Fecal Occult Blood is a quick test which can be done to test for microscopic traces of blood in the stool. A positive test is almost always an indication to do a colonoscopy. In most cases the positive result is just due to
Hemorrhoids ; however, it can also be due to
Polyps (which are easily removed during the colonoscopy procedure),
Diverticulosis , inflammatory bowel disease (
Crohn's Disease ,
Ulcerative Colitis ), or colon cancer.
Due to the high mortality associated with colon cancer and the high effectivity and low risks associated with colonoscopy, it is now also becoming a routine screening test for people 50 years of age or older. Subsequent rescreenings are then scheduled based on the initial results found, with a five- or ten-year recall being common for colonoscopies that produce normal results.
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 fibre or clear-fluid only diet. Examples of clear fluids are apple juice,
Bouillon , artificially flavored lemon-lime soda or sports drink, and of course water. As orange juice, prune juice, and milk contain fibre, they are banned from the list, as are liquids dyed red, orange, purple, or brown, such as cola or coffee. On the day before the colonoscopy, the patient is either given a
Laxative preparation (such as
Bisacodyl ,
Phospho Soda ,
Sodium Picosulfate , or
Sodium Phosphate and/or
Magnesium Citrate ) and large quantities of fluid or
Whole Bowel Irrigation is performed using a solution of
Polyethylene Glycol and
Electrolytes .
