Gastric Ultrasound Versus Gastroscopic Aspiration

Study Procedure and Conduct Each participant enrolled in the study will undergo a standardized two-step assessment protocol, consisting of a preoperative gastric ultrasound followed by a gastroscopy with complete aspiration of gastric contents. These procedures will be performed within a maximum interval of one hour, and conducted at Fribourg Cantonal Hospital within the Departments of Anesthesiology and Gastroenterology. All examinations will be performed by trained and credentialed operators, adhering to validated clinical protocols. Following the acquisition of written informed consent, baseline demographic and clinical data will be collected. Gastric ultrasound will then be performed using a portable ultrasound device equipped with a low-frequency curvilinear transducer. The patient will be positioned sequentially in the supine and right lateral decubitus positions, with the upper body inclined at 45°, to obtain sagittal views of the gastric antrum. Antral diameters (antero-posterior and cranio-caudal) will be measured in each position, and the cross-sectional antral area (CSA) will be calculated accordingly. The estimated gastric volume (EGV) will be derived using the validated formula proposed by Perlas et al. Gastric contents will be classified into three qualitative grades (Grade 0 to 2), enabling stratification of aspiration risk. Within one hour of the ultrasound, a diagnostic gastroscopy will be performed by an experienced gastroenterologist, following routine clinical practice. Immediately upon endoscope insertion and prior to any irrigation, complete aspiration of gastric contents will be performed to allow accurate measurement of the intragastric volume. The contents will be assessed macroscopically for appearance (e.g., clear, cloudy, bilious, alimentary) and consistency (liquid or solid). The aspirated volume will be quantified using a calibrated, graduated container. Based on visual assessment, the stomach will be classified as empty, partially full, or full. All collected data will be documented using standardized case report forms and entered into a secure, anonymized database for subsequent statistical analysis.