Which imaging test is NOT recommended for evaluating large bowel obstruction?

Barium enema is not recommended for evaluating large bowel obstruction primarily due to the risk of complications and its limited efficacy in these situations. When a large bowel obstruction is present, the use of a barium enema can lead to perforation of the bowel, especially if the obstruction is complete or if there is significant distension. Additionally, the barium can cement an impaction and make subsequent surgical intervention more complicated.

In contrast, other imaging modalities like CT scans and Gastrografin enemas provide valuable information in assessing the degree and location of obstruction without the same level of risk. Sigmoidoscopy can be useful for decompressing the obstructed segment, particularly in cases of large bowel obstruction originating in the rectum or sigmoid colon. Therefore, the preference for these other diagnostic tests over a barium enema in cases of large bowel obstruction underscores the potential dangers and limitations associated with the latter.