Plain radiographs of the abdomen, consisting of the upright, supine, and left lateral decubitus views, are inexpensive and easy to obtain.

The information gained is most helpful in the patient with acute abdominal pain or in the perioperative period. The presence of a pneumoperitoneum, dilated loops of bowel with air fluid levels, and displacement of normal loops of bowel can be indicative of perforation, obstruction or organ enlargement, respectively.

Plain abdominal radiographs are useful in detecting calcifications associated with such diseases as chronic pancreatitis, cholelithiasis, and nephrolithiasis. Barium studies are obtained using water-soluble agents(Hypaque, Gastrografin) or different concentration of barium. Water-soluble agents are helpful in the identification of perforations, and they result in less tissue reaction with the peritoneum than barium. Water-soluble contrast agents can also identify colonic obstructing lesions because the retention of barium can be problematic when surgery is indicated. Barium is the agent of choice in patients suspected of having aspiration or a tracheoesophageal fistula because it is associated with less pulmonary toxicity. Single-contrast studies involve the administration of a barium bolus and can detect liminal narrowing, obstruction, or large lesions. The double-contrast technique involves the administration of a small amount of high-density barium followed by the instillation of air or gas-forming agents. The fine coating of the hollow produces higher study that is more sensitive for the detection of smaller mucosal lesions. Cine-esophagography involves the dynamic assessment of the swallowing function and esophageal motility. This test is useful for detecting abnormalities in the phase of swallowing, documenting aspiration risk, assessing the adequacy of esophageal peristalsis, and identifying esophageal motility disorders. Single-contrast esophageal studies can detect pression on the esophagus by an enlarged thyroid, left atrium, or mediastinal tumor.

It is also useful for detecting esophageal masses, tumors, or strictures. The use of a barium impregnated marshmallow or tablet can demonstrate more subtle strictures and rings. Double-contrast esophagography is more sensitive for the detection of mucosal lesions such as erosions, ulcers, webs, and rings . A single-contrast upper gastrointestinal barium study is useful for detecting gastric ulcers, luminal narrowing, and disordered motility characterized by poor gastric emptying.

A double-contrast study allows for the identification of more subtle lesions, such as gastric erosions and abnormalities at anastomotic sites, and can be helpful in assessing thickened gastric or duodenal folds.