Objective To analyze the occurrence of acute gastrointestinal injury (AGI) after pediatric cardiac surgery with cardiopulmonary bypass (CPB) and its impact on prognosis, and to explore the risk factors and early warning indicators for AGI, in order to identify and diagnose AGI at an early stage. Methods This is a prospective observational study. The patients under 14 years with congenital heart disease receiving surgeries with CPB who were admitted to the pediatric ICU of West China Hospital, Sichuan University from December 2020 to December 2021 were included. The general information, perioperative gastrointestinal symptoms and intra-abdominal pressure, surgery-related information, postoperative organ function and prognosis of the children were collected. The patients were divided into an AGI group and a non-AGI group according to the 2012 European Society of Critical Care Medicine AGI diagnostic criteria. ResultsA total of 137 patients were enrolled, including 68 males and 69 females with a median age of 20.0 (6.0, 43.0) months. There were 60 patients in the AGI group and 77 patients in the non-AGI group, with an AGI incidence of 43.80%. The incidences of overall adverse outcomes, low cardiac output syndrome, and infectious complications were higher in the AGI group, and the vasoactive-inotropic score (VIS), mechanical ventilation time, ICU stay, and hospital stay were higher or longer in the AGI group, the differences were statistically significant (P<0.001). AGI was an independent risk factor for the overall adverse outcomes (OR=3.191, 95%CI 1.187 to 8.579, P=0.021). Univariate and multivariate logistic regression analyses indicated that weight, male, CPB time and intraoperative VIS were independent predictors for AGI after pediatric cardiac surgery. The receiver operating characteristic curve indicated that the patients with an intraoperative VIS>10.5 points and CPB time>96.5 min might have a higher possibility of postoperative AGI. ConclusionThe incidence of AGI in pediatric cardiac surgery with CPB is high, and it is an independent risk factor for overall adverse outcomes. Weight, male, CPB time , and intraoperative VIS are independent risk factors for AGI.