What is it?
A colonoscopy is a simple procedure that allows your doctor to look inside the entire large intestine. It is frequently performed to detect early signs of cancer in the colon and rectum. The test also may be done to obtain a tissue sample for biopsy, diagnose inflammatory bowel disease or evaluate unexplained abnormalities (such as polyps), anemia, blood in the stool, abdominal pain or persistent diarrhea.
Preparation for a colonoscopy usually begins several days before the actual procedure. Because the colon and rectum must be completely clean to ensure accurate test results, your doctor may ask you not to eat solid foods for two to three days and to follow a liquid diet. Drink clear liquids such as juice or broth to prevent dehydration. A laxative or enema may be necessary the night before the test. Keep taking regularly-prescribed medication unless advised otherwise by your doctor.
You will be given a moderate sedative and pain medication to help you relax and keep you comfortable during the exam. A rectal exam may be done before a colonoscopy to dilate the rectum and check for obstructions. A flexible tube called a colonoscope is then inserted into the rectum and slowly guided into the colon. Images of your colon are transmitted by the colonoscope onto a video screen so your doctor can examine the intestinal lining. Polyps can be removed using tiny tools inserted through the scope. Tissue samples will be sent to the lab to determine if they are cancerous.
Polyps are abnormal growths on the intestinal wall that can range in size from a small dot to as large as several inches. Most polyps are non-cancerous, but because cancer begins in polyps, your doctor will probably remove them to prevent colorectal cancer. Your doctor also may take tissue samples to test for inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease. Bleeding in the colon can be treated by special medications, laser, heater probe or electrical probe passed through the colonoscope.
What can I expect?
You will be given pain medication and a mild sedative prior to the exam. These medications will help you relax and keep you comfortable during the exam. You will lie on your left side on the examining table. Your physician will insert a long, flexible, lighted tube into your rectum and slowly guide it into your colon. The tube is called a colonoscope. It contains a tiny camera that will transmit an image of the inside of your colon so your physician can examine the lining. You may be asked to change position occasionally to help the physician move the scope. The scope also blows air into your colon to inflate it and help the physician see better.
If anything abnormal is seen in your colon, like a polyp or inflamed tissue, the physician can remove all or part of it using tiny instruments passed through the scope. The tissue is sent to a lab for testing. If there is bleeding in the colon, the physician can pass probes or inject special medicines through the scope to stop the bleeding.
The exam generally takes 30 to 60 minutes. You will need to stay at the facility for one to two hours until the sedative wears off. You will not be allowed to drive home after the procedure because of sedatives you will take prior to the procedure, so arrange for someone to come with you to drive you home.
Virtual Colonoscopy: A Less Invasive Alternative
A virtual colonoscopy uses computers and magnetic resonance imaging or CT scans to produce multi-dimensional images of the colon and rectum without a colonoscopy. Preparation for the procedure is similar to regular colonoscopy, but no sedative is used, and patients can resume normal activities immediately. Virtual colonoscopy can generate many views of the colon, but flat lesions and polyps less than 10 millimeters in diameter may not be detected.