Contrast Techniques of GI Tract, Biliary Tract, Genito-Urinary Tract In Radio-Diagnosis.

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. Visualization of the gastrointestinal tract with ultrasound may be difficult because intraluminal air produces an echogenic shadow, which prevents the sound beam from penetrating structures posteriorly. The scattering and reflection