In a double contrast BE, which part of the large intestine is likely to be filled with barium during the PA recumbent projection?

• A. Ascending colon
• B. Descending colon
• C. Transverse colon
• D. Sigmoid colon

Answer: (C)

In a double contrast barium enema (BE), the specific positioning, including the PA recumbent projection, plays a crucial role in determining which portions of the large intestine are filled with barium. In this projection, the patient lies on their stomach, and the x-ray beam is directed posteriorly.

When the patient is in this position, gravity causes barium to flow naturally toward the most dependent parts of the large intestine. The transverse colon, being centrally located and at a higher position relative to the other segments of the colon when the patient is recumbent, collects barium effectively in this projection. As a result, the barium coats the walls and fills this segment adequately, allowing for optimal imaging.

The other portions of the colon may not be as prominently filled with barium during this projection, especially if they are positioned in areas that are less favorable for barium to collect due to the influence of gravity and patient positioning. Therefore, the transverse colon is the area most likely to be filled with barium in a PA recumbent projection, making this the correct choice for the question.