During a double contrast BE, which projection can illustrate the posterior wall of the rectum?

• A. Ventral decubitus, lateral rectum
• B. AP axial
• C. PA axial
• D. Right lateral decubitus

Answer: (A)

In a double contrast barium enema (BE), the ventral decubitus lateral rectum projection is particularly effective for demonstrating the posterior wall of the rectum. This projection is designed to visualize this specific area by allowing the barium to fill the rectum while the patient is in a position that minimizes superimposition from other anatomical structures. By placing the patient in the ventral decubitus position, the posterior wall of the rectum is rotated and thus more clearly seen on the radiographic film.

The use of double contrast enhances the visibility of the mucosal lining and any lesions or abnormalities that may be present. In this position, the barium contrasts well against the air in the lumen of the rectum, making it easier to identify pathologies like polyps or lesions on the posterior wall.

Other projections may not adequately expose the posterior wall in the same way. They could show other structures or might not provide the required contrast between air and barium necessary for optimal visualization. Therefore, for clear illustration of the posterior wall of the rectum during a double contrast BE, the ventral decubitus lateral rectum projection is the most suitable choice.