During a double contrast BE, which position is best suited to show the lateral wall of the ascending colon and the medial wall of the descending colon?

• A. Left lateral decubitus
• B. Right lateral decubitus
• C. Supine
• D. Trendelenburg

Answer: (A)

The left lateral decubitus position is particularly effective during a double contrast barium enema (BE) because it allows for optimal visualization of the anatomy in question. In this position, the patient's left side is down, which takes advantage of the barium's tendency to coat the lateral wall of the ascending colon while allowing air to rise and fill the medial wall of the descending colon. This configuration provides a clear view of both walls, enhancing diagnostic accuracy.

When the patient is in the left lateral decubitus position, gravitational forces assist in the separation of barium and air within the colon. The barium settles and coats the ascending colon, while the air rises to outline the descending colon, contributing to a more comprehensive assessment of any potential abnormalities.

The other positioning options do not provide the same level of clarity for the specific structures being targeted. For example, the right lateral decubitus position may effectively highlight other parts of the colon but is less suited for the specific visualization needed in this scenario. The supine and Trendelenburg positions would not facilitate the separation of air and barium in a way that optimizes the imaging of the ascending and descending colons.