Pulmonary aspiration of gastric content is a serious anesthetic complication. Gastric point-of-care ultrasound can determine the type and volume of gastric content when clinical information is equivocal. However, a cutoff value of either antral cross-sectional area or volume that may be considered as the upper limit of normal in fasting subjects is still controversial. The aim of this study is to characterize the distribution of baseline antral area and volume in fasting adult subjects and to identify an upper limit (95th percentile) of these distributions.


The authors conducted a meta-analysis of individual participant data of primary studies from an academic research network of investigators collaborating in gastric ultrasound. Studies between January 2009 and December 2020 were included.


Twelve primary studies met inclusion criteria and were included in the analysis with a sample size of 1,203 subjects. The 95th percentile of area values (measured in the right lateral decubitus) was 9.9 cm2 (95% CI, 9.4 to 10.4), and of volume, 2.3 ml/kg (95% CI, 2.3 to 2.4). In addition, an antrum grade 0 or 1 indicates a 98% probability of an antral area below the 95th percentile.


An area of 10 cm2 measured in the right lateral decubitus could be a simple, data-driven upper limit of antral area that could serve as a surrogate of upper limit of normal gastric volume values in fasting adults. These results are limited by the highly selected sampling of the studies included.

Editor’s Perspective
What We Already Know about This Topic
  • Gastric point-of-care ultrasound can be used to determine volume of gastric contents, which may be useful in defining aspiration risk in patients receiving general anesthesia
What This Article Tells Us That Is New
  • The cutoff values for antral cross-sectional area and volume that define the upper limit of normal in fasted subjects has not been established
  • By conducting a meta-analysis of individual patient-level data from 1,203 subjects drawn from 12 primary studies, the demonstrated the 95th percentile of area values when patients were in the left lateral decubitus was 9.9 cm2 and a volume of 2.3 ml/kg
  • These measures can be used to define the upper limit of normal for fasted subjects using point-of-care ultrasound, which may have clinical utility in establishing aspiration risk