Colonoscopy

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 at least 24 hours before your procedure 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.

Virtual Colonoscopy

A Less Invasive Alternative

A virtual colonoscopy uses computers and magnetic resonance imaging or computed tomography scans to produce multi-dimensional images of the colon and rectum without a colonoscope. Preparation for the procedure is similar to a regular colonoscopy, but no sedative is used and patients can resume normal activities immediately after the test. Virtual colonoscopy can generate many views of the colon, but flat lesions and polyps less than 10 millimeters in diameter may not be detected. A regular colonoscopy would be performed to remove polyps detected during a virtual exam.

Most colonoscopy procedures last approximately 30 minutes to one hour, plus two to three hours for preparation and recovery. You may feel pressure or bloating during the procedure, but discomfort usually can be reduced by taking slow, deep breaths. After the exam you may pass gas and experience mild abdominal cramping. The sedative should wear off in a couple of hours. You should be able to return to normal activities by the next day.