Doctor's Responses Archive

Viewer Question:
What are the reasons for a physician prescribing a Barium Enema? Why not colonoscopy or virtual colonoscopy?
Doctor's Response:
Barium enema and/or colonoscopy are performed for a variety of reasons. Most often they are performed to investigate the finding of blood in the stool, abdominal pain or a change in the bowel habits (constipation or diarrhea). Colonoscopy is also frequently performed for colon polyp and cancer screening.

A lower GI series, or barium enema, is an x-ray test in which a white liquid, called barium, is placed into the rectum and colon through the anus to enhance x-ray pictures of the large bowel (colon). These x-rays are used to define normal and abnormal anatomy of the colon and rectum. Colon and rectal abnormalities that can be detected include diverticulosis, diverticulitis, abnormal colon movement, narrowing or dilation of the colon, polyps, and cancers. Barium enema generally is not as accurate as colonoscopy or virtual colonoscopy. Barium enema can miss (fail to detect) polyps or sometimes even cancers. Barium enema also has difficulty detecting colitis involving the superficial lining of the colon. Barium enema also cannot obtain samples (biopsies) or remove (excise) polyps. Therefore patients found to have abnormalities on barium enemas often need to undergo colonoscopy for verification, clarification or treatment.

Colonoscopy is a procedure that enables an examiner (usually a gastroenterologist) to evaluate the inside of the colon (large bowel). This is accomplished by inserting a flexible tube with a camera on the end that is about the thickness of a finger into the anus, and then advancing the tube slowly through the entire colon. It is performed with the endoscopist viewing the image transmitted by the camera to a TV monitor. Colonoscopy is more accurate than barium enema in detecting polyps, cancers, and colitis. Colonoscopy also has the added advantage of being able to remove polyps and obtain biopsies (tiny tissue samples for analysis under a microscope) at the same time of the procedure. (Removing polyps helps prevent colon cancer). Therefore colonoscopy is the preferred procedure for colon polyp and cancer screening for healthy adults as well as for adults at higher than normal risk of colon cancer.

Virtual colonoscopy is an x-ray procedure to image the colon using a sophisticated CAT scan machine. It is believed to be almost as accurate as colonoscopy in detecting cancer and polyps greater than 5 mm in size. It is less "invasive" than colonoscopy. (It involves infusing air into the colon via the rectum but without the need for insertion of a long tube into the colon as with colonoscopy.) It has an added advantage of being able to examine other organs (ovaries, liver, kidneys, etc.) at the same time. Virtual colonoscopy, however, cannot remove polyps or perform tissue biopsies. Therefore, patients found to have polyps or other abnormalities with virtual colonoscopy must undergo colonoscopy for polyp removal and diagnosis of other abnormalities. Virtual colonoscopy also has difficulty detecting colitis and flatter polyps. I believe that virtual colonoscopy will be a useful alternative to colonoscopy in selected patients, though its exact role will need to be defined in the coming years. Please remember, information can be subject to interpretation and can become obsolete. Therefore, information should never be a substitute for an open and trusting doctor-patient relationship. Always consult your doctor.

Thank you for your question.
Last Editorial Review: 4/16/2002