Objective:To identify the risk factors for preoperative full stomach in the patients undergoing emergency surgery.Methods:American Society of Anesthesiologists physical status Ⅰ-Ⅲ patients of both sexes, aged≥18 yr, with body mass index ≥15 kg/m 2, scheduled for elective emergency surgery, were included.The operation bed was adjusted to 30° head-high and feet-low position.Ultrasound images of gastric antrum were observed in the right decubitus position, and the ultrasonic images were evaluated qualitatively and quantitatively.The ultrasonic image was qualitatively assessed as having empty antrum, liquid or solid.Three images were obtained during the diastolic period of gastric antrum when quantitative assessment was performed.The longest diameter (D1) and the widest diameter (D2) of the images were measured three times and averaged to calculate the cross-sectional area of gastric antrum [CSA=(D1×D2×π)/4]. The gastric volume was calculated [GV=27.0+ (14.6×CSA)-(1.28×age)]. When the result was<0, the gastric volume was 0.GV/body weight was calculated, and GV/body ≤1.5 ml/kg was considered as empty stomach.When gastric content was solid or GV/body weight>1.5 ml/kg, it was considered as full stomach.Patients were divided into 2 groups according to whether they presented with a full stomach: empty stomach group (group E) and full stomach group (group F). The patients′ fasting time, coexisting diseases and types of operation were recorded.Multivariate logistic regression analysis was performed on the indicators with statistically significant differences between groups to identify the risk factors for preoperative full stomach in the patients undergoing emergency surgery. Results:One hundred and seventy-nine cases were finally included, with 121 cases in group E and 58 cases in group F. Compared with group E, the fasting time was <6 h, and the incidence of coexisting diabetes was increased in group F ( P<0.05). Coexisting diabetes mellitus was an independent risk factor for preoperative full stomach in the patients undergoing emergency surgery ( P<0.05), and OR (95% confidence interval) was 11.968 (2.392-59.870). Conclusion:Coexisting diabetes mellitus is an independent risk factor for preoperative full stomach in the patients undergoing emergency surgery.