X-Ray and Other Imaging Contrast Studies of the Gastrointestinal Tract

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.

A small-bowel meal is done by using fluoroscopy and provides a more detailed evaluation of the small bowel.

Shortly before the examination, the patient is given metoclopramide 20 mg orally to hasten transit of the contrast material.

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.

Glucagon 0.5 mg IV can facilitate the examination by causing gastric hypotonia.

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. Enteroclysis has largely been replaced by CT or MR enterography CT enterography and MR enterography X-ray and other imaging contrast studies visualize the entire gastrointestinal tract from pharynx to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... read more .

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.