In critical ill patients, feeding protocol is one of the important factor which determines the successful implementation of enteral nutrition（EN）. Acute gastrointestinal injury(AGI) affects feeding tolerance, which greatly determines the successful implementation of feeding protocol. In our previously study, we found that transabdominal intestinal sonography is helpful to diagnosis AGI. Thus in this study ,we apply transabdominal gastrointestinal sonography to feeding protocol, to assess the feasibility of gastrointestinal sonography assisted enteral nutrition and its impact on critical ill patients.

Patients meeting inclusion and exclusion criteria were randomly assigned to the intervention group and control group. During the first week of initiation of nutrition, enteral nutrition was conducted according to different procedures to observe the impact of different feeding procedures on clinical indicators

Inclusion Criteria:

• The age is not less than 18 years
• within 24 hours after entering ICU
• Acute Physiology and Chronic Health Evaluation II (APACHE II) score > 8
• the estimated length of stay in ICU is more than 3 days
• informed consent

Exclusion Criteria:

• The normal anatomy of stomach, small intestine or the right colon was significantly changed (Gastrectomy, esophagectomy, pancreaticoduodenectomy, gastrointestinal bypass surgery, the presence of short bowel syndrome,etc.)
• Uncontrolled gastrointestinal bleeding
• Uncontrolled intestinal obstruction
• Uncontrolled mesenteric vascular disease
• Pregnancy
• breastfeeding
• Received enteral nutrition or parenteral nutrition within 24 hours prior to ICU admission
• Predict death within 48 hours after ICU admission
• Enrolled in this study before.