Objective: To determine the usefulness of quantifying residual gastric volume measured by ultrasound in the preoperative period, for the timely identification of patients at risk of bronchoaspiration. Materials and methods: We present the results of a prospective, observational, analytical, cross-sectional study performed on patients scheduled for surgery in order to calculate gastric volume by ultrasound. Results: 150 patients were evaluated. The prevalence of at-risk stomach was 12.7% (19 cases). The factors associated with at-risk stomach are: gender, since men had a probability 2.6 [95% CI 1.0-7.3] times higher than women of suffering from it (p = 0.05); smoking with a probability 4.3 [95% CI 1.9-12.2] times higher of at-risk stomach compared to non-smokers (p = 0.03). Conclusion: Gastric ultrasound is a validated tool to noninvasively assess gastric volume and content and thus predict the risk of pulmonary aspiration.