Pulmonary aspiration of gastric contents remains one of the most serious complications in anesthetic practice. Despite advances in fasting guidelines, airway management, and perioperative safety protocols, aspiration continues to contribute substantially to anesthesia-related morbidity and mortality.

Preoperative gastric ultrasonography has emerged as an important point-of-care tool for evaluating residual gastric contents and estimating aspiration risk. However, uncertainty remains regarding which ultrasound measurement plane provides the most accurate assessment of gastric volume.

A newly published prospective observational study by Liu et al. in Anesthesiology evaluated differences between gastric ultrasound measurements obtained at the abdominal aorta and inferior vena cava (IVC) planes. The findings suggest that neither plane is consistently superior, but selecting the higher-measured gastric volume may yield the most accurate estimate of actual gastric volume and aspiration risk.

What is gastric ultrasonography?

Gastric ultrasonography is a bedside imaging technique used to estimate gastric content volume and assess the risk of pulmonary aspiration before anesthesia.

The examination typically focuses on the gastric antrum while the patient is positioned in the right lateral decubitus position.

Clinicians commonly use two anatomical approaches:

• Abdominal aorta plane
• Inferior vena cava (IVC) plane

Both techniques utilize vascular landmarks to identify and measure the gastric antrum.

Why this study matters

Current gastric volume prediction models accept measurements from either the abdominal aorta or IVC planes.

Previous studies have used:

• Abdominal aorta plane only
• IVC plane only
• Either plane interchangeably

However, anatomical differences between these planes may influence gastric volume estimation and potentially affect aspiration risk assessment.

The investigators sought to determine:

• Whether the two measurement planes provide different gastric volume estimates
• Which plane most accurately reflects the actual gastric volume
• Whether one approach improves the detection of high aspiration risk patients

Study design

The researchers conducted a prospective observational study at Guangzhou University of Chinese Medicine.

The study enrolled healthy adult volunteers between July and August 2025.

Participant criteria included:

• Age greater than 18 years
• BMI ≤30 kg/m²
• ASA physical status I or II
• Ability to undergo gastric ultrasonography

A total of 202 volunteers were recruited.

Six participants were excluded because a clear visualization of the gastric antrum could not be obtained.

Final analysis included 196 participants.

Study protocol

The researchers evaluated gastric volume in two states.

1. Low gastric volume state

Participants:

• Fasted for at least 8 hours
• Avoided water for 2 hours
• Underwent gastric ultrasonography at both measurement planes

1. High gastric volume state

Participants then consumed apple juice at 2.3 mL/kg body weight

This amount corresponds to the currently accepted threshold associated with a full stomach and elevated aspiration risk.

Ultrasound measurements were repeated after ingestion.

Participant demographics

Baseline characteristics included:

• Median age: 23 years
• Median BMI: 20.97 kg/m²
• 48.5% male
• 51.5% female
• Median examination time: 2.5 minutes

Main findings

Significant differences between measurement planes

Researchers found statistically significant differences in abdominal aorta and IVC measurements between fasting and post-ingestion states.

After fluid ingestion:

Abdominal aorta plane

• Predicted gastric volume: 3.64 ± 1.11 mL/kg
• Mean gastric volume: 213.13 mL

IVC plane

• Predicted gastric volume: 3.11 ± 0.83 mL/kg
• Mean gastric volume: 180.94 mL

The abdominal aorta plane consistently produced larger gastric volume estimates.

The higher measured volume was most accurate

Investigators categorized measurements into:

• Abdominal aorta plane
• IVC plane
• Higher-measured gastric volume plane
• Lower-measured gastric volume plane

The most important finding was that the higher-measured gastric volume plane most closely matched the actual ingested volume.

Only this approach showed no statistically significant difference between predicted and actual gastric volume.

Key findings included:

• Mean bias: −4.27 mL
• P = 0.076 versus actual volume
• Smallest measurement error among all approaches

Aspiration risk detection

The researchers also evaluated how effectively each measurement strategy identified patients with high aspiration risk.

Predicted ingested volume detection rates:

• Higher-measured gastric volume plane: 45.41%
• Abdominal aorta plane: 37.25%
• IVC plane: 19.90%
• Lower-measured gastric volume plane: 12.25%

High gastric volume state detection rates

• Higher-measured gastric volume plane: 95.41%
• Abdominal aorta plane: 90.31%
• IVC plane: 81.63%
• Lower-measured gastric volume plane: 76.53%

Why the planes may differ

The authors propose an anatomical explanation.

The IVC plane is located closer to the pylorus, a region that is less distensible than the gastric antrum.

As gastric volume increases:

• Gastric expansion becomes more pronounced
• Distension varies by location
• Measurement discrepancies widen

This may explain why differences between planes were larger after fluid ingestion than during fasting.

Clinical implications

The findings may have important implications for perioperative practice.

Potential benefits include:

• Improved gastric volume estimation
• More accurate aspiration risk stratification
• Better perioperative decision-making
• Enhanced patient safety
• More individualized anesthesia planning

The authors recommend distinguishing between the abdominal aorta and IVC planes and using the higher measured gastric volume when applying current predictive models.

Limitations

The investigators acknowledged several limitations:

• Single-center study
• Relatively young and healthy participants
• BMI limited to ≤30 kg/m²
• Results may not generalize to all surgical populations
• Ultrasound examinations were performed by an experienced operator
• Acceptable limits of agreement for gastric ultrasound remain undefined

Additional studies are needed to validate these findings in broader patient populations.

Key takeaways

• Gastric ultrasound measurements differ significantly between the abdominal aorta and the IVC planes
• Measurement discrepancies increase as gastric volume rises
• Neither plane is consistently superior
• The higher measured gastric volume most closely reflects actual gastric volume
• Using the higher value may improve the aspiration risk assessment
• Current predictive models may benefit from incorporating measurement-plane differences

Future directions

Future research may explore:

• Development of plane-specific prediction models
• Validation in obese patients
• Evaluation in emergency surgery populations
• Application in patients with delayed gastric emptying
• Integration with artificial intelligence-assisted image analysis
• Multicenter validation studies

Conclusion

This prospective observational study provides important new evidence that the selection of the ultrasound measurement plane significantly influences gastric volume estimation.

Rather than relying exclusively on either the abdominal aorta or IVC plane, clinicians may improve the accuracy of aspiration risk assessment by evaluating both views and using the higher measured gastric volume when applying current prediction models.

As gastric ultrasonography becomes increasingly integrated into perioperative care, these findings may help refine risk stratification and improve patient safety during anesthesia. For more information, refer to the full article in Anesthesiology.

For more information, refer to the full article by Liu et al. in Anesthesiology.

Liu H, He Y, Ding L, et al. Multiplanar Ultrasonographic Assessment of Gastric Volume: A Prospective Observational Study. Anesthesiology. 2026;144(6):1299-1308.

Learn gastric ultrasound and more with NYSORA’s POCUS App!