Imaging of the hollow organs of the gastrointestinal tract began over a century ago with the use of heavy metal salts. Barium sulfate suspensions emerged as the contrast agent of choice for examination of the gastrointestinal tract. By the 1970s, other imaging modalities, including endoscopy and computed tomographic (CT) examination, appeared and have developed into alternate ways of imaging the hollow gastrointestinal organs.
The emergence and advancements in these newer technologies have dramatically affected the use of luminal contrast examinations of the gastrointestinal tract. In this chapter, I first describe the examination techniques that are currently available to evaluate the gastrointestinal tract. Normal imaging of the hollow organs as seen on a variety of examining modalities is discussed and illustrated. Technique selection is reviewed, with its effects on patient preparation and clinical indications. Finally, a series of exercises based on the more common clinical presentations of gastrointestinal tract disorders shows a wide variety of pathologic conditions.
Luminal contrast examinations of the gastrointestinal tract can be performed with a variety of contrast materials. Barium sulfate suspensions are the preferred material for most examinations. A variety of barium products are available commercially, and many are formulated for specific examinations depending on their density and viscosity. Water-soluble contrast agents, which contain organically bound iodine, are used less often, primarily to demonstrate perforation of a hollow viscus or to evaluate the status of a surgical anastomosis in the gastrointestinal tract. The details and various options available for luminal contrast examination depend on the organ(s) being evaluated and are further elaborated in the normal imaging section.
Computed Tomographic Imaging
CT imaging of the chest and abdomen can portray the various hollow organs of the gastrointestinal tract. Mucosal disease, such as ulcers, and small neoplasms will not be shown with this imaging modality. Larger gastrointestinal neoplasms, thickening of the walls of the hollow organs, and extrinsic processes can be easily detected. Also, with the use of luminal distention and intravenous contrast material, a variety of gastrointestinal disorders are more readily evaluated.
A major role of CT scanning, especially in the esophagus and colon, is staging malignancy of these organs. In the colon, for example, CT examination is used for initial staging, especially for distant metastases, and for evaluation of recurrence following surgery. Recurrent masses appearing after surgery may also be biopsied percutaneously. CT colonography (CTC) is yet another expanding application for colon cancer screening and detection of polyps and malignancies of the large bowel.
Magnetic Resonance Imaging
Magnetic resonance (MR) imaging is the newest modality developed for cross-sectional imaging of the body and nearly all organ systems can be evaluated with this technique. MR imaging of the hollow organs of the gastrointestinal tract is increasingly being used to evaluate a wide assortment of gastrointestinal tract disorders. As with CT imaging, mild mucosal diseases ...