A virtual colonoscopy is a medical procedure in which x-rays, computed tomography (CT), or magnetic resonance imaging (MRI) is used in tandem with computers to create and display images of the colon. The procedure creates two- and three-dimensional images that can be used to diagnose various diseases of the colon and rectum, including diverticulosis, polyps, and cancer. A virtual colonoscopy can be used to examine the colon from its lowest end, the rectum, to the beginning of the small intestine. It can also display the right colon, the cecum, which cannot be seen completely in one in ten patients undergoing a traditional colonoscopy.
A virtual colonoscopy is more comfortable and convenient for the patient than a traditional colonoscopy. It does not require sedation, takes less time than a regular colonoscopy, and does not require any recovery time. In addition, it provides better images than a barium enema x-ray, and unlike traditional colonoscopy, it provides visual access to areas outside the colon.
In a traditional colonoscopy, a colonoscope, a flexible tube with camera attached, is inserted into the rectum to meet the end of the small intestine, and images are taken as the scope is retracted over a course of 20 to 25 minutes. The procedure is uncomfortable and the patient is often sedated, in which case the patient cannot drive himself home and must undergo a recovery period of 30 to 60 minutes. Preparation for a traditional colonoscopy is also inconvenient and time consuming, as the patient is often required to follow a restricted liquid diet for three days before the procedure in order to ensure that the colon is free of solid matter.
To prepare for a virtual colonoscopy, the patient typically takes a laxative at home the day before the procedure in order to clear the colon of solid matter. A suppository may also be used to cleanse the area. The patient will also be given a solution that coats any fecal matter remaining in the colon in order to make it visible to the radiologist, so that it will not be interpreted as polyps or other abnormal growths.
Virtual colonoscopy takes only ten minutes. First, a thin tube is inserted in the rectum and air is pumped in to expand the rectum and facilitate viewing. The patient is photographed first in a prone or face-down position on an examination table, and then in a supine or face-up position. While the patient is in each position, the table moves through a scanner, which captures the images. The patient must hold his or her breath while the images are produced in order to prevent distortion.
The major drawback of virtual colonoscopy is that it does not allow for immediate biopsy or removal of polyps in the case of positive results. However, a patient can undergo traditional colonoscopy right after a virtual colonoscopy if necessary. Virtual colonoscopy also does not provide images as detailed as those possible with traditional colonoscopy, so very small polyps may not be detectable. Many doctors prefer traditional colonoscopies to virtual ones, and the former remain standard procedure.