The contralateral decubitus chest film.

The radiology and emergency medicine literature have emphasized the value of the cross-table decubitus chest film taken with the hemithorax containing the suspected pathology in the dependent position. When used in conjunction with the upright chest film, the contralateral decubitus film (with the side of interest up) often reveals more information than does the film with the side of interest dependent. The unsuspected bilaterality of pleural effusion, especially when subpulmonic, often is revealed, as is pathology in the lung base that is obscured by large effusion or cardiomegaly. Masses, cavities, and areas of consolidation may become apparent. Especially important in pediatric patients, vascular structures can be distinguished from infiltrate. The contralateral decubitus film should be obtained when examinations in other positions have yielded equivocal results, rather than repeating an examination. This avoids unnecessary radiation exposure and is cost effective. Because of their complementary nature, in many cases both decubitus views should be obtained.