A colonoscopy and a barium enema are both diagnostic tools used to examine the large intestine, or colon, but they function differently. Colonoscopy is the standard procedure, using a flexible tube with a camera to directly visualize the colon’s inner lining, allowing for immediate biopsy or removal of polyps. The barium enema is a radiographic examination where a liquid contrast agent is introduced into the rectum to coat the colon’s interior wall. X-ray images are then taken to create a structural map of the organ. When the initial colonoscopy cannot be completed, the barium enema serves as a necessary follow-up to ensure the entire colon has been assessed for abnormalities.
Why Colonoscopy Procedures Are Sometimes Incomplete
An incomplete colonoscopy occurs when the endoscope cannot be advanced all the way to the cecum, the beginning of the large intestine. The procedure’s success is often hampered by technical limitations and the patient’s unique anatomy. A common obstacle is a redundant or tortuous colon, meaning the colon is longer than average and has excessive looping or sharp bends that prevent the scope from navigating smoothly.
Anatomical factors like fixed strictures, areas of abnormal narrowing, can physically block the passage of the colonoscope. Adhesions, or internal scar tissue from previous abdominal surgeries, can fix sections of the colon in place, leading to acute angulation that is challenging to bypass. These difficulties mean that a segment of the colon, most often the upper or right side, remains visually unexamined, necessitating an alternative method to complete the diagnostic workup.
The Unique Information Provided by a Barium Enema
The barium enema offers a distinct perspective by focusing on the overall shape and structure of the colon rather than mucosal surface detail. Unlike the direct visual inspection of a colonoscopy, the enema uses X-ray technology with a barium suspension to outline the entire length and inner contour of the bowel. The contrast agent coats the wall, allowing the radiologist to assess the colon’s diameter, length, and any areas of narrowing or dilation that a scope could not fully pass.
When air is also introduced, creating a double-contrast study, the barium film provides a clearer profile of the inner lining and any subtle structural changes. This method is adept at detecting the extent of a stricture or an obstructing mass by showing how the colon’s lumen is affected. The X-ray images can also reveal extrinsic compression, which occurs when an abnormality outside the colon is pressing on the bowel wall.
Specific Medical Indications for the Follow-Up Procedure
The decision to proceed with a barium enema after an incomplete colonoscopy is driven by the need to meet cancer screening standards, which require a full colon evaluation. When technical factors prevent the scope from reaching the cecum, the unexamined segment remains a potential site for undetected pathology. The follow-up procedure is indicated when certain pathologies are suspected or encountered that make scope passage difficult or impossible.
Severe diverticular disease, characterized by numerous small pouches in the colon wall, can make advancing the colonoscope risky or technically challenging due to rigidity and narrowing. A large obstructing mass, potentially a tumor, may be seen, but its full size, location, and relationship to adjacent structures are better mapped through the barium enema’s structural view. If a stricture caused the incomplete examination, the barium enema helps determine if the narrowing is benign, possibly due to inflammation, or suspicious for malignancy.
What to Expect During the Barium Enema
Because the colon was already cleansed for the colonoscopy, no further extensive bowel preparation is required for the barium enema. The procedure usually takes between 30 and 60 minutes and is performed by a radiologist or a radiology technician. You will be asked to change into a gown and lie on the examination table, often on your side.
A small, lubricated tube is inserted into the rectum, and the barium suspension flows slowly into the colon. During this process, you may feel a sensation of fullness or mild cramping in the lower abdomen. The table will be moved, and you will be asked to change positions multiple times to help the barium coat the inner surface of the colon. The radiologist uses fluoroscopy, a form of continuous X-ray, to watch the barium flow and capture static images.
Once the imaging is complete, the majority of the barium is drained out through the tube, and you will be directed to a bathroom to expel the remainder. There is no sedation used, so you can resume normal activity immediately afterward. For a few days, your bowel movements will appear lighter in color due to the passing of the chalky white barium.