X-Ray Contrast Studies of the Abdomen
X-ray and other imaging contrast studies visualize the entire gastrointestinal tract from pharynx to rectum and are most useful for detecting mass lesions and structural abnormalities (eg, tumors, strictures).
Single-contrast studies fill the lumen with radiopaque material, outlining the structure. Better, more detailed images are obtained from double-contrast studies, in which a small amount of high-density barium coats the mucosal surface and gas distends the organ and enhances contrast. The gas is injected by the operator in double-contrast barium enema, whereas in other studies, intrinsic gastrointestinal tract gas is adequate. In all cases, patients turn themselves to properly distribute the gas and barium. Fluoroscopy can be used to monitor the progress of the contrast material. Either video or plain films can be taken for documentation, but video is particularly useful when assessing motor disorders (eg, cricopharyngeal spasm, achalasia).
The main contraindication to x-ray contrast studies is
Suspected perforation
Perforation is a contraindication because free barium is highly irritating to the mediastinum and peritoneum; water-soluble contrast is less irritating and may be used if perforation is possible. Older patients may have difficulty turning themselves to properly distribute the barium and intraluminal gas.
Complications of abdominal x-ray contrast studies are rare. Perforation can occur if barium enema is done in a patient with toxic megacolon. Barium impaction may be prevented by postprocedure oral fluids and sometimes laxatives.
Barium enema
A barium enema can be done as a single- or double-contrast study. Single-contrast barium enemas are used for potential obstruction, diverticulitis, fistulas, and megacolon. Double-contrast studies are preferred for detection of tumors.
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Small-bowel meal
A small-bowel meal is done by using fluoroscopy and provides a more detailed evaluation of the small bowel.
Upper gastrointestinal examination
An upper gastrointestinal examination is best done as a biphasic study beginning with a double-contrast examination of the esophagus, stomach, and duodenum, followed by a single-contrast study using low-density barium.
Enteroclysis
CT Scanning of the Abdomen
CT scanning using oral and IV contrast allows excellent visualization of both the small bowel and colon as well as of other intra-abdominal structures.
CT colonography
CT colonography (virtual colonoscopy) generates 3D and 2D images of the colon by using multidetector CT and a combination of oral contrast and gas distention of the colon. Viewing the high-resolution 3D images somewhat simulates the appearance of optical endoscopy, hence the name. Optimal CT colonography technique requires careful cleansing and distention of the colon. Residual stool causes problems similar to those encountered with barium enema because it simulates polyps or masses. Three-dimensional endoluminal images are useful to confirm the presence of a lesion and to improve diagnostic confidence.
CT enterography and MR enterography
gastrointestinal bleeding, small-bowel tumors, chronic ischemia), a biphasic contrast-enhanced MDCT study is done.
CT enterography and CT colonography have largely supplanted standard small-bowel series, enteroclysis, and barium enema examinations.
Magnetic resonance (MR) enterography can also be used in a similar fashion to CT enterography. It is typically reserved for younger patients, especially those with inflammatory bowel disease, to reduce lifetime radiation exposure risk. MR enterography is more expensive than CT enterography.
