Which imaging technique is indicated for diagnosing a small bowel obstruction?

The choice of a CT abdomen and pelvis with per os (PO) contrast for diagnosing a small bowel obstruction is optimal because this imaging technique provides detailed cross-sectional images of the abdominal cavity, allowing for the clear visualization of the small bowel. CT scans are particularly effective in identifying the location, type, and cause of the obstruction, as they can reveal distended loops of bowel, transition points, and even associated complications such as perforation or ischemia.

Using PO contrast enhances the diagnostic capability of the CT scan by providing better delineation of bowel structures and helping to assess patency. This contrasts with other modalities, as X-rays may show signs of obstruction, but they offer limited detail compared to a CT scan. Ultrasound is more operator-dependent and often less effective for visualizing small bowel structures in adults, while an MRI can be useful in specific contexts but is not typically the first-line imaging test for suspected obstructions due to lower availability and the time it takes to perform.

In cases of small bowel obstruction, clinicians prioritize modalities that provide comprehensive information quickly, and CT with PO contrast meets these criteria effectively.