Nutritional support for CD Patients with perioperative CD mostly have nutritional problems and should receive nutritional support – parenteral nutrition or elemental diet therapy before surgery to improve nutritional status in the short term and create favorable conditions for surgery; postoperative sequential therapy and early EN are used to facilitate postoperative recovery. The nutritional calorie target for critically ill patients in the acute stress period is 20-25 kcal/(kg×d), which should not be too high, and can be increased appropriately after the state is stabilized. Advantage of enteral nutrition (EN) As long as the function of gastrointestinal tract allows and it is safe, EN treatment is preferred. If the digestive function is impaired, pre-digested enteral nutrition liquid preparation (short peptide type, amino acid type) can be used to overcome gastrointestinal intolerance and reduce PN; if necessary, a tube can be placed; the biggest advantage of EN is the protection of intestinal mucosal barrier, because it can directly give mucosal nutrition, promote gastrointestinal hormone and gastrointestinal fluid secretion, and protect probiotic flora. Studies have shown that the important mechanisms of action of EN are the protection of intestine-associated lymphoid tissue, maintenance of intestinal barrier function, and reduction of the risk of infection and complications. Compared with PN, EN is more physiological and can reduce complications, length of hospital stay and medical costs. there are two major types of EN tube feeding routes: non-invasive placement techniques, mainly via the nasogastric route, and invasive placement techniques, including minimally invasive (e.g., percutaneous endoscopic gastrostomy) and surgical stoma techniques.