The colonoscopy is an examination of the colon using an instrument called a colonoscope. The colonoscope has a camera and light at the tip of a long, thin, flexible tube. The physician directs it around bends in the colon as it transmits images of the colon lining to a large video monitor. Channels that allow the physician to pass instruments through for biopsies run through the tube. The physicians can also take pictures and video.
Reasons for Colonoscopy
The American Cancer Society recommends that everyone should have colon cancer screening by the age of 50 (or possibly earlier in some cases) to detect and prevent colon cancer. Colonoscopy provides the means not only to detect but also to remove any precancerous lesions called polyps, if found.
Colonoscopy can also be used to diagnose and possibly treat other problems in the colon. These include vascular abnormalities, inflammatory bowel disease and infectious colitis. Medical history, physical exam, laboratory tests and x-rays can provide important information, but in many cases, colonoscopy is necessary for definitive diagnosis.
Preparation for Colonoscopy
The colon must be clean and free of stool for an optimal exam. Most physicians require patients to perform bowel cleansing the day before the colonoscopy. Each physician's exact bowel cleanse differs slightly, but most usually require a clear liquid diet at least one to two days prior to the procedure, followed by laxatives and possibly enemas. Most of these laxatives require physician prescription. Certain medications may also need to be held prior to the procedure, but this varies with individual problems. Therefore, patients must make sure to give the physician a complete list of medications.
The Procedure
The procedure mostly occurs on an outpatient basis. Patients usually receive intravenous anesthesia delivered by the physician performing the procedure or by an anesthesiologist. This form of anesthesia is called conscious sedation. Sedated patients breath spontaneously but feel no pain and do not recall the procedure afterward. Once the anesthesia takes effect, the colonoscope is inserted into the anus and moved gently through the colon so that the entire colon lining can be inspected. If the physician sees a polyp, he can lasso it with a thin wire snare and apply electrical heat to painlessly remove it. Other tests can be performed during colonoscopy, including biopsy to obtain tissue specimens for microscopic analysis on any abnormal-appearing tissue.
Recovery
The colonoscopy takes 15 to 30 minutes and is seldom remembered by the sedated patient. Patients usually need 30 to 60 minutes in a postanesthesia area to recover from sedation. Bloating and cramping typically occur for about an hour after the exam until the air is expelled. Patients need someone to drive them home, as the effect of sedation can impair the ability to drive. For the remainder of the day, patients should not drive, operate machinery or make important decisions. They should rest and drink plenty of fluids. Normal activity can resume the following day.
Possible Complications
Serious complications from colonoscopy are uncommon. One possible complication is excessive bleeding, especially with the removal of a large polyp. Another serious but rare complication is perforation of the colon. This can be from the colonoscope tearing open a hole or from excessive tissue destruction during a polyp removal. Both bleeding and perforation may require hospitalization and possibly surgery. Finally, a diagnostic error or oversight may occur, as no test is 100 percent accurate. Fortunately, all of these complications are unusual.
Alternatives to Colonoscopy
Alternative tests to colonoscopy include radiographic exams such as barium enema, virtual colonoscopy or computed tomography (CT) scan. These tests provide outlines of the colon lining and may allow for diagnosis. However, these tests may still require bowel cleansing and do not allow direct viewing of the colon, removal of polyps or performance of biopsies.
Study of stool and blood can provide information about some colon conditions like infectious colitis or inflammatory bowel disease. These tests may provide the suggestion of colon cancer but are not specific enough to be diagnostic. If these tests are positive, a colonoscopy may be indicated.
