Justification from literature

PROJECTION FOR GASTROENTERITIS

AP SUPINE ABDOMEN PROJECTION 

The AP (anteroposterior) supine abdominal projection is generally the first and often most suitable imaging option in cases where gastroenteritis is suspected with symptoms severe enough to require imaging. The AP supine view provides a clear picture of bowel gas distribution, allowing radiologists to assess for signs of bowel distention, gas buildup, or abnormal air-fluid levels. While these findings are not specific to gastroenteritis, they help rule out other conditions that may mimic its symptoms, like bowel obstruction or paralytic ileus.