Plain Radiographs and Barium Contrast Studies



Plain radiographs of the abdomen in the supine and upright or lateral decubitus positions are sim­ple to obtain and relatively inexpensive; unfor­tunately, they provide information of value in only a few select circumstances. They are highly sensitive for clinical entities that involve abnor­mal gas patterns such as bowel obstruction, per­foration of a hollow organ (free intraperitoneal air), and infections with gas-forming organisms (emphysematous cholecystitis) and are usually the first test obtained when these entities are con­sidered. Plain films are also useful in detecting intra-abdominal calcifications such as gallbladder or renal stones or pancreatic calcifications in chronic alcoholic pancreatitis.

Contrast studies using barium sulfate (or oc­casionally the water-soluble iodinated contrast agent Gastrografin) provide more information about the anatomy of the tubular gastrointestinal tract. Single-contrast studies are performed using a bolus of contrast material and generally detect mass lesions but frequently miss small or mucosal lesions. Double-contrast studies, in which barium, is administered first followed by a radiolucent substance such as air to produce a thin layer of barium coating the mucosa, are better able to de­tect all types of lesions, including those confined to the mucosa.

Single- and double-contrast barium swallows detect esophageal strictures and masses, and dou­ble-contrast studies may detect lesions of the mu­cosa such as ulcerations or varices. Endoscopy, which may miss submucosal mass lesions, is much more sensitive for mucosal lesions. Use of fluoroscopy during a barium swallow, particu­larly when combined with cine or video recordings, allows evaluation of esophageal motility dis­orders.

The standard single- or double-contrast exam­ination of the upper gastrointestinal tract (upper GI series) is widely used to detect gastric mass lesions, gastric ulcers, and duodenal ulcers. Major changes in gastric motility can be evaluated using fluoroscopy, and markedly reduced motility may provide the first clue to a submucosal gastric can­cer, a disease often difficult to detect by endos­copy. Most gastric ulcers (benign and malignant) are visualized radiographically; however, it is not possible to identify correctly all malignant ulcers on the basis of their radiographic appearance, so that biopsy is generally recommended. Double-contrast upper GI examinations may detect mu­cosal disorders such as erosive gastritis, MalloryWeiss tears, stress ulcers, and anastomotic ulcers; however, endoscopy is more sensitive for such le­sions. Overall, in the initial evaluation of common clinical problems such as dysphagia and epigas­tric pain, the upper GI series remains a primary diagnostic imaging test.

Satisfactory radiographic examination of the small bowel is more difficult to achieve owing to pooling and dilution of barium during passage through the small bowel and to obscuring of bowel segments by overlapping loops. The stan­dard small bowel series can evaluate the caliber of the small bowel and provide some information regarding bowel mucosa, wall thickness, and fluid transit time, particularly in the proximal bowel. Mass lesions, obstructions, and fistulas are usu­ally detected. An improved view of the entire small bowel can be obtained by performing a small bowel enema (enteroclysis) in which bar­ium, followed by radiolucent methylcellulose so­lution, is delivered directly into the jejunum via an orogastric tube. A small bowel series is gen­erally utilized when evaluating malabsorption, inflammatory bowel disease, or bowel obstruc­tion. Endoscopic techniques to visualize the small bowel beyond the C-loop of the duodenum are not available.

Single- and double- (pneumocolon) contrast (or “air-contrast”) radiographs of the colon have long been the standard for identifying lesions in the colon. With the use of pneumocolon, radiographic detection of even subtle lesions such as polyps and early inflammatory bowel disease is excel­lent, although generally colonoscopy detects more lesions and allows a more thorough exam­ination of the rectum. Therefore, the choice of doublecontrast barium enema or colonoscopy to evaluate patients with occult fecal blood, sus­pected inflammatory bowel disease, a tumor, diar­rhea, or obstruction often depends upon the need for tissue for histological examination and the availability, cost, and comfort of the procedure.

The studies discussed thus far are usually per­formed using barium sulfate as the contrast agent. Watersoluble iodinated compounds, which produce images of lesser quality and are more ex­pensive, are generally used only when a perfo­ration is suspected (as barium is toxic when it escapes into body cavities) or when a colonic ob­struction is suspected (barium caught above a coIonic obstruction will dehydrate and possibly worsen the obstruction, whereas the watersolu­ble agents will not).