Contrast agents such as iodine-based water-soluble contrast and barium are dense on X-ray and can be used to outline the GI and urinary tract. When using barium in the GI tract it is possible to then distend the organ with gas (low density contrast) to obtain a barium-coated (double contrast) examination, which provides finer mucosal detail.

Investigation of the gastrointestinal tract

With the increased availability of endoscopy services and the use of CT-based techniques like CT pneumocolon and 3D colonography, fewer fluoroscopic contrast examinations of the GI tract are performed. However, contrast examinations are dynamic and provide some functional information. Some very specific questions, such as the course of a fistula, are often best assessed fluoroscopically.

The successful and safe completion of contrast study of the GI tract depends on:

1. Appropriate patient preparation. See table overleaf for a summary of preparation procedures for the most common contrast studies of the GI tract. Local guidelines for appropriate antibiotic cover for patients at risk of developing endocarditis after rectal intubation should be confirmed with the microbiology department.

2. Adequate clinical information to ensure that the correct contrast mediumand motility agent are used for a study. For example, the use of barium in the setting of a suspected perforation is potentially fatal. See Table below. The GI effects of motility agents are unfortunately non-specific. A relevant history of the conditions listed in Table 131.3 is helpful.

CASE STUDY

JS, a 58-year-old lady, had been following a smooth postoperative course after an anterior resection of a Dukes' B adenocarcinoma of the lower sigmoid.