Ultrasonographic gastric antral diameter as a bedside indicator of intragastric volume in critically Ill patients receiving enteral nutrition via gastrostomy

Purpose: Enteral nutrition delivered via gastrostomy is commonly used for long-term nutritional support in critically ill patients. Monitoring gastric residual volume (GRV) is commonly used to evaluate tolerance to enteral feeding and reduce the risk of regurgitation and aspiration. However, conventional GRV measurement by aspiration through a nasogastric tube is invasive and may not accurately reflect true gastric contents. Gastric ultrasonography has emerged as a non-invasive bedside tool for evaluating gastric contents and estimating gastric volume. Nevertheless, data regarding the use of gastric ultrasonography in enterally tube-fed intensive care unit (ICU) patients remain limited. Methods: This prospective observational study included 50 critically ill patients receiving enteral nutrition via gastrostomy. Gastric antral diameter was measured using ultrasonography at baseline and after sequential administration of 100, 200, 300, 400, and 500 mL of enteral feeding solution. Measurements were repeated to assess reproducibility. Statistical analysis included Wilcoxon signed-rank test, Spearman correlation, linear regression analysis, and receiver operating characteristic (ROC) curve analysis. Results: Gastric antral diameter increased progressively with intragastric volume (p < 0.001). Significant correlations were observed between repeated measurements at lower volume levels (r = 0.321–0.612). Linear regression analysis demonstrated a strong relationship between antral diameter and gastric volume (R² ≈ 0.88, p < 0.001), with the equation: gastric volume (mL) = − 72 + 21.5 × antral diameter (mm). ROC analysis showed excellent diagnostic performance for predicting clinically relevant gastric volumes. The optimal cut-off value was 16 mm for predicting ≥ 200 mL (AUC = 0.93, 95% CI: 0.88–0.98), 18 mm for ≥ 300 mL (AUC = 0.93, 95% CI: 0.88–0.98), and 19 mm for ≥ 400 mL (AUC = 0.91, 95% CI: 0.85–0.96). Conclusion: Ultrasonographic measurement of gastric antral diameter increases significantly with increasing intragastric volume in critically ill patients receiving enteral nutrition. Gastric ultrasound is a practical, non-invasive, and reproducible bedside tool for monitoring gastric volume changes in critically ill patients receiving enteral nutrition. Its use may enhance feeding tolerance assessment and guide enteral nutrition management in the ICU.