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 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 Achalasia Achalasia is a neurogenic esophageal motility disorder characterized by impaired esophageal peristalsis and a lack of lower esophageal sphincter relaxation during swallowing. Symptoms are slowly... read more ).
The main contraindication to x-ray contrast studies is
Perforation Acute Perforation of the Gastrointestinal Tract Any part of the gastrointestinal tract may become perforated, releasing gastric or intestinal contents into the peritoneal space. Causes vary. Symptoms develop suddenly, with severe pain followed... read more 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.
Patients having upper gastrointestinal x-ray contrast studies must have nothing by mouth (npo) after midnight. Patients having barium enema follow a clear liquid diet the day before, take an oral sodium phosphate laxative in the afternoon, and take a bisacodyl suppository in the evening. Other laxative regimens are effective.
Complications of abdominal x-ray contrast studies are rare. Perforation can occur if barium enema is done in a patient with toxic megacolon Toxic colitis Ulcerative colitis is a chronic inflammatory and ulcerative disease arising in the colonic mucosa, characterized most often by bloody diarrhea. Extraintestinal symptoms, particularly arthritis... read more . Barium impaction may be prevented by postprocedure oral fluids and sometimes laxatives.
A barium enema can be done as a single- or double-contrast study. Single-contrast barium enemas are used for potential obstruction Intestinal Obstruction Intestinal obstruction is significant mechanical impairment or complete arrest of the passage of contents through the intestine due to pathology that causes blockage of the bowel. Symptoms include... read more , diverticulitis Colonic Diverticulitis Diverticulitis is inflammation with or without infection of a diverticulum, which can result in phlegmon of the bowel wall, peritonitis, perforation, fistula, or abscess. The primary symptom... read more , fistulas Anorectal Fistula An anorectal fistula is a tubelike tract with one opening in the anal canal and the other usually in the perianal skin. Symptoms are discharge and sometimes pain. Diagnosis is by examination... read more , and megacolon. Double-contrast studies are preferred for detection of tumors.
Enteroclysis (small-bowel enema) provides still better visualization of the small bowel but requires intubation of the duodenum with a flexible, balloon-tipped catheter. A barium suspension is injected, followed by a solution of methylcellulose, which functions as a double-contrast agent that enhances visualization of the small-bowel mucosa.
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 (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 provides optimal visualization of the small-bowel mucosa; it is preferably done by using a multidetector CT (MDCT) scanner. Patients are given a large volume (1350 mL) of 0.1% barium sulfate before imaging. For certain indications (eg, obscure gastrointestinal bleeding Overview of Gastrointestinal Bleeding Gastrointestinal (GI) bleeding can originate anywhere from the mouth to the anus and can be overt or occult. The manifestations depend on the location and rate of bleeding. (See also Varices... read more , small-bowel tumors Small-Bowel Tumors Small-bowel tumors account for 1 to 5% of gastrointestinal tumors. Small-bowel cancer accounts for an estimated 11,110 cases and about 1,700 deaths in the US annually (1). Diagnosis is by enteroclysis... read more , 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.
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