Critical patients aging from 18 to 80 years old diagnosed with acute lower gastrointestinal dysfunction were recrutied to the study. The two following criterias should met for the diagnosis of acute lower gastrointestinal dysfunction: 1. enteral nutrition intolerance not due to upper gastriointestinal obstruction; 2. Colonic distension: colonic diameter >6 cm or ileocecus diameter >9 cm under the view of computed tomography or abdomial X ray. Enteral nutrition intolerance was defined as enteral feeding < 50% caculated needs or no feeding for three days.