An interventional study of Gastric Ultrasound in Aspiration Risk, Full Stomach Status and Gastric Content, sponsored by Hôpital Fribourgeois. Not yet recruiting at 1 site in Switzerland. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2025-12-24.
Sponsored by Hôpital Fribourgeois · Not applicable, Interventional, and Diagnostic
This is a prospective, single-center observational study conducted at the Fribourg Cantonal Hospital to evaluate the diagnostic performance of preoperative gastric ultrasound in determining gastric content and volume. Upper gastrointestinal endoscopy with complete suction of gastric contents serves as the reference standard.
Adult patients (≥ 18 years) scheduled for elective or urgent gastroscopy are consecutively recruited. A gastric ultrasound is performed within one hour before the endoscopic procedure. The antral cross-sectional area is measured in standardized positions (supine and right lateral decubitus), and gastric volume is estimated using validated formulas. Gastric content is categorized into three grades (empty, low-risk liquid content, or high-risk/solid content).
During gastroscopy, complete aspiration of gastric contents is performed at the start of the procedure. The aspirated volume and qualitative characteristics (liquid vs. solid) are recorded, and the stomach is classified as empty, partially full, or full by the endoscopist.
The primary objective is to determine the accuracy of gastric ultrasound in identifying a full stomach. Secondary objectives include evaluating the qualitative agreement between ultrasound and gastroscopy, correlating estimated gastric volume with aspirated volume, and identifying an optimal ultrasound-based volume threshold predictive of a full stomach.
Approximately 1,390 patients will be enrolled over one year to obtain at least 139 "full stomach" cases, based on prevalence estimates and sample size calculations. Statistical analyses will include diagnostic performance metrics, Cohen's kappa, correlation tests, Bland-Altman plots, and ROC curve analysis.
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.
Hôpital Fribourgeois is the lead sponsor of 15 studies on the registry; 9 are open to participants now.
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Exclusion Criteria:
Single Group - Diagnostic Assessment
Diagnostic Test: Gastric Ultrasound
All enrolled participants undergo a preoperative gastric ultrasound within one hour prior to the scheduled gastroscopy. The gastric antrum is measured in standardized positions, and estimated gastric volume is calculated.
the diagnostic accuracy of gastric ultrasound in identifying a full stomach, using gastroscopy with aspiration as the reference standard.
Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy of preoperative gastric ultrasound in identifying a full stomach, compared to gastroscopy with complete aspiration of gastric contents. Gastric content is classified as empty, low-risk liquid content, or high-risk/solid content.
Time frame: Within 1 hour prior to gastroscopy
Correlation coefficient between ultrasound-estimated gastric volume and aspirated gastric content volume during gastroscopy
Gastric volume is estimated by preoperative ultrasound and compared with the volume of gastric content aspirated during gastroscopy. The Pearson or Spearman correlation coefficient is calculated depending on data distribution.
Time frame: Within 1 hour prior to gastroscopy
Cohen's kappa coefficient for agreement between ultrasound and gastroscopy regarding gastric content nature
Agreement between gastric ultrasound and gastroscopy for classification of gastric content nature (clear liquid, turbid liquid, solid) is assessed using Cohen's kappa coefficient.
Time frame: Within 1 hour prior to gastroscopy
Optimal estimated gastric volume (EGV) threshold for predicting a full stomach
Determination of the optimal threshold of estimated gastric volume (EGV) measured by preoperative ultrasound for predicting a full stomach, using receiver operating characteristic (ROC) curve analysis. Sensitivity, specificity, and area under the ROC curve (AUC) will be calculated.
Time frame: Within 1 hour prior to gastroscopy
Plan to share: Yes — The shared individual participant data (IPD) will include only the data used in the publication of the study results, specifically: * Gastric ultrasound measurements (antral cross-sectional area, estimated gastric volume, gastric content grade) * Gastroscopy findings (aspirated gastric volume, qualitative gastric content classification) * Basic participant characteristics (age, sex, weight)
Supporting information: Study protocol, Sap
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Hôpital Fribourgeois