A 50-year male with paroxysmal abdominal pain for 6 days，nausea and abdominal distension for days admitted to the ER. Physical examination showed abdominal bulge and visible peristalsis. Active bowl sound and gurgling could be heard by auscultation. X-ray showed fluid level in the dilated small intestine in the middle abdomen and a small a-mount of gas in the colon. The most possible diagnosis is ：