Principles of performance and interpretation of double-contrast gastrointestinal studies

Successful use of double-contrast techniques requires skill both in performing and interpreting the examination. To perform the examination properly, great care must be taken in evaluating the coating of the mucosal surface. An appropriate barium suspension designed for double-contrast radiography must be used. The necessity of varying the degree of gaseous distention for demonstrating certain types of lesions must also be appreciated. To interpret these examinations, the radiologist must understand the factors contributing to the radiographic image--the dependent and nondependent surfaces and the pool of barium. A firm understanding of both the uses and drawbacks of the pool of barium not only is helpful in the performance of the examination but also is essential for accurate interpretation. A knowledge of the differing appearances of structures on the dependent and nondependent surfaces is of the most utmost importance because this knowledge can be used to obtain a three-dimensional view of both elevated and depressed lesions. An accurate correlation of this picture with the gross pathologic appearance of a lesion is the aim of the double-contrast technique.