Examining the colon for abnormalities and polyps often calls for a special diagnostic procedure known as a barium enema, or lower G.I. (gastrointestinal) exam. Because a standard x-ray image cannot provide a well-defined picture of soft tissues such as the colon, a contrasting agent must be applied to provide more definition. In the case of a barium enema, this contrasting agent is a metallic powder called barium sulfate.
Before a barium enema can begin, the patient is usually required to maintain a clear liquid diet to clear out any remaining stool from the colon. A standard enema may be used to make sure the colon is as clear as possible. Fecal material can block the view of certain sections of the colon if not removed. Once the patient has been prepped, he or she is dressed in a hospital gown and led to an examination room.
The barium enema process itself starts with the injection of the barium sulphate suspension into the patient's colon through the rectum. This can be a notoriously uncomfortable experience, and many patients feel a sense of fullness or the urge to defecate while the barium sulphate is introduced. A small balloon prevents the contrasting agent from leaking out through the rectum. Once the barium sulphate has been fully dispensed, the radiologist may ask the patient to assume several different positions in order to coat every section of the colon. Some direct pressure may even be applied to the patient's pelvis or abdomen in order to ensure maximum coverage.
After the barium sulphate has been injected and adjusted, the radiologist shoots a number of x-ray images from different angles. Because the barium sulphate appears white on a standard x-ray, any dark areas are examined very carefully for signs of abnormality. If more definition is desired, the initial barium enema may be followed by the injection of air into the colon. The patient is allowed to expel the barium sulphate in a private bathroom, but there is generally enough residue to provide contrast for this second examination. Not all barium enema procedures involve the use of air to inflate the colon, but it is believed that the improved contrast is worth the extra time and effort. Smaller polyps may be difficult to discover through a standard barium enema alone.
The standard age at which a barium enema exam is generally encouraged is 50, although people with a family history of colorectal problems may opt to have one performed earlier. Most people can afford to wait 5-10 years between barium enema exams, but those who exhibit other signs of colorectal cancer or have questionable results from a first exam may want to undergo the procedure more often. A barium enema is considered a less invasive alternative to a complete colonoscopy, which may have to be performed under anesthesia. A barium enema can provide many of the same answers as a colonoscopy without the added discomfort and recovery time.