This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Small & Large Intestine, Subject name: Surgery
[{'content': 'How to differentiate mechanical obstruction from paralytic ileus? \nSelect and explain. \nA. Elevation of hemi diaphragm, B. Absence of rectal shadow, C. Multiple air fluid levels, D. Abdominal distension', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) Absence of rectal shadowRef: Bailey and Love 26th edition, Page 1190* The important point to differentiate paralytic ileus and mechanical obstruction in X-ray is there will be absence of rectal gas shadow in mechanical obstruction.* Clinically bowel sounds will be absent in paralytic ileus with no pain.', 'role': 'assistant'}]