Virtual Colonoscopy

Your body absorbs nutrients and removes waste products via your digestive system.  Whenever you eat and drink, food travels through your digestive system for processing.  As water from the waste product is absorbed, the product becomes more solid and forms a stool or feces.  It is eventually eliminated from your body when you have a bowel movement.

After you swallow food, it moves through your esophagus and into your stomach.  Chemicals in your stomach break down the food into a liquid form.  The processed liquid travels from your stomach to your small intestine.  Your small intestine breaks down the liquid even further so that your body can absorb the nutrients from the food you ate.  The remaining waste products from the small intestine travel to the large intestine.

Your large intestine, also called the large bowel or colon, is a tube that is about 5 feet long and 3 or 4 inches around.  The lower GI tract is divided into sections, including the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal, and anus.  The appendix is located on the cecum, but it does not serve a purpose in the digestive process. 
 
The first part of the colon absorbs water and nutrients from the waste products that come from the small intestine.  As the colon absorbs water from the waste product, the product becomes more solid and forms a stool.  The large intestine moves the stool into the sigmoid colon, where it may be stored before being traveling to the rectum.  The rectum is the final 6-inch section of your digestive tract.  No significant nutrient absorption occurs in the rectum or anal canal.  From the rectum, the stool moves through the anal canal.  It passes out of your body through your anus when you have a bowel movement.

TEST USES

A virtual colonoscopy may be ordered for several reasons.  It is most frequently used to diagnose colorectal cancer and polyps.  However, it is not recommended as a screening tool for colorectal cancer by American Cancer Society.  A virtual colonoscopy can also be used to identify digestive or inflammatory diseases including diverticulosis and other tumors.  It is helpful for determining the cause of bleeding.  Additionally, a virtual colonoscopy may be used as a follow-up assessment after a colonoscopy.

PREPARATION

A virtual colonoscopy is an outpatient procedure that is performed in the radiology department of a hospital or medical center.  The procedure does not require sedation or anesthesia.  Preparation instructions for a virtual colonoscopy generally consist of methods to empty or clean your bowel prior to the test including the use of laxatives, enemas, or a liquid diet.  Your doctor will provide you with specific instructions.  You will need to remove all jewelry, dentures, metal hair clips, body piercing jewelry, and other metal items that might show up on a scan before your procedure.

THE PROCEDURE

You will wear an examination gown for the procedure.  To begin, you will lie on your left side on an examination table.  A thin flexible tube will be gently placed through your anus and into your rectum.  Air will be administered through the tube to inflate your colon.  Making the colon bigger provides a better view and allows a more thorough examination.  After the air is inserted, you will lie on your back.

The table will move through the opening of a scanning machine that will take images of your colon.  The procedure may use magnetic resonance imaging (MRI) or computed tomography (CT) scans.  You will be asked to remain still and hold your breath at times while the images are taken.  You may be asked to change positions to provide pictures from different angles.  The images are sent to a computer that compiles them into a three-dimensional (3D) picture of your colon.  When the procedure is completed, the thin tube is carefully withdrawn.

The procedure may cause temporary discomfort from the air that is pumped into the colon.  You may feel temporary abdominal cramping or gas pain.  MRI and CT scanning are painless procedures.  They simply require that you remain motionless while the pictures are taken.  You may return to work or your normal activities after the procedure.  Your doctor will instruct you on how to increase your food and liquid intake.

A radiologist will evaluate the images from your virtual colonoscopy.  If abnormal results were found by your test, your doctor will discuss next step planning with you.  If a polyp is found on a virtual colonoscopy, it needs to be examined and possibly removed with a colonoscopy.