Washed Microbiota Transplantation for Malnutrition After Nonphysiological Reconstruction of the Upper Gastrointestinal Tract

Inclusion Criteria: * Patients undergone nonphysiological reconstruction of the gastrointestinal tract (such as Billroth-II, Roux-en-Y, Child, Whipple reconstruction) * Aged over 18 years old; * Malnutrition is assessed by Nutritional Risk Screening 2002 score≥3 and Patient Generated Subjective Global Assessment (PG-SGA) score≥4; * Written informed consent; Exclusion Criteria: * Expected survival time \< 3 months; * Still on anti-tumor therapy or it is expected during the visit; * Complicated with ascites or edema caused by malnutrition; * Known organic gastrointestinal disease (e.g., gastrointestinal infection, inflammatory bowel disease, or radiation enteritis); * Undergone other gastrointestinal surgery (e.g., enterectomy, enterostomy, or gastrostomy) except appendectomy or anal fistula surgery; * Complicated with contraindications of enteral nutrition such as ileus, active gastrointestinal bleeding, and shock; * Cannot tolerate gastroscopy or colonoscopy; * Severe comorbidities (e.g., diabetes, cardiopulmonary failure, severe liver or or kidney diseases); * Complicated with other wasting diseases (e.g., active tuberculosis, hyperthyroidism, diabetes, HIV, active hepatitis, hip fracture, craniocerebral injury, etc.); * A history of anti-infective treatment within 30 days before enrollment; or need anti-infective treatment at the time of enrollment; or unwilling to stop taking drugs that affect gut microbes, such as probiotics; * Can not tolerate oral enteral nutrition; * Women who are pregnant or breastfeeding; * Participating in another clinical trial; * Deemed unsuitable for inclusion by the investigators.