(BE, Lower Gastrointestinal Series, Lower GI Series, Colon X-ray)
What is a barium enema?
A barium enema is a radiographic (X-ray) examination of the lower gastrointestinal (GI) tract. The large intestine, including the rectum, is made visible on X-ray film by filling the colon with a liquid suspension called barium sulfate (barium). Barium highlights certain areas in the body to create a clearer picture.
X-rays use invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs on film. X-rays are made by using external radiation to produce images of the body, its organs, and other internal structures for diagnostic purposes. X-rays pass through body tissues onto specially-treated plates (similar to camera film) and a "negative" type picture is made (the more solid a structure is, the whiter it appears on the film).
Fluoroscopy is often used during a barium enema. Fluoroscopy is a study of moving body structures—similar to an X-ray "movie." A continuous X-ray beam is passed through the body part being examined, and is transmitted to a TV-like monitor so that the body part and its motion can be seen in detail. In a barium enema, fluoroscopy allows the radiologist to see the movement of the barium through the large intestine as it is instilled through the rectum.
Why is barium used with X-rays?
Barium is a dry, white, chalky, metallic powder that is mixed with water to make barium liquid. Barium is an X-ray absorber and appears white on X-ray film. When instilled via the rectum, barium coats the inside wall of the large intestine so that the inside wall lining, size, shape, contour, and the colon's patency are visible on X-ray. This process shows differences that might not be seen on standard X-rays. Barium is used only for diagnostic studies for the GI tract.
The use of barium with standard X-rays contributes to the visibility of various characteristics of the large intestine. Some abnormalities of the large intestine that may be detected by a barium enema include tumors, inflammation, polyps (growths), diverticula (pouches), obstructions, and changes in the intestinal structure.
After the instillation of barium into the rectum, the radiologist may also fill the large intestine with air. Air will appear black on X-ray film, contrasting with barium's white image. The use of the two substances, barium and air, is called a double contrast study.
The purpose of using two contrast substances is to achieve an enhancement of the inside wall lining of the large intestine. As the air expands the large intestine (like blowing up a balloon), a barium coating is formed on the inner surface of the colon wall. This technique enhances visualization by sharpening the outline of the inner surface layer of the large intestine. The benefit of this technique is to show smaller surface abnormalities in the large intestine.
Other related procedures that may be used to diagnose lower GI problems include colonoscopy, abdominal X-ray, CT (computed tomography) scan of the abdomen, and abdominal ultrasound. Please see these procedures for additional information.
Anatomy of the colon
The large intestine, or colon, has four sections:
Ascending colon. Extends upward on the right side of the abdomen
Transverse colon. Extends from the ascending colon across the body to the left side
Descending colon. Extends from the transverse colon downward on the left side
Sigmoid colon. Named because of its S-shape; extends from the descending colon to the rectum
The rectum joins the anus, or the opening where waste matter passes out of the body.
Reasons for the procedure
A barium enema may be performed to diagnose structural or functional abnormalities of the large intestine, including the rectum. These abnormalities may include, but are not limited to:
Ulcerative colitis. Ulcerations and inflammation of the large intestine
Crohn's disease. Ulcerations and inflammation occurring in any part of the GI tract (mouth to anus)
Obstructions and polyps (growths)
Unusual bloating or lower abdominal pain
Unexplained weight loss
Irritable bowel syndrome
Changes in bowel movements. Such as chronic diarrhea or constipation, or passing of blood, mucus, and/or pus