Qualitative and quantitative ultrasonography can reliably differentiate between a full and empty stomach. However, no prior studies have correlated gastric volume with actual intraoperative regurgitation or aspiration events. This study investigated the relationship between ultrasonographically measured gastric antral cross-sectional area and the occurrence of regurgitation in parturients, to inform ultrasonographic diagnostic criteria for predicting regurgitation risk.

Eighty parturients undergoing urgent cesarean section under general anesthesia were enrolled. Upon arrival in the operating room, patients were positioned in a semirecumbent position for gastric ultrasound assessment. Subsequently, an esophageal pH electrode was inserted nasally. After rapid sequential induction intubation, anesthesia was maintained with sevoflurane and nitrous oxide. Mid-esophageal pH was monitored in real time until 10 min after extubation to detect occult regurgitation. The receiver operating characteristic curve assessed the predictive ability of antral cross-sectional area for regurgitation in parturients; associations between potential covariates and regurgitation occurrence were assessed using multivariable logistic regression.

Regurgitation was observed in 34 parturients (one overt and 33 occult), with no cases of clinically significant aspiration occurring. The optimal antral cross-sectional area cut-off for predicting regurgitation was 487.7 mm ² (area under the receiver operating characteristic curve: 0.876; 95% confidence interval: 0.80–0.95). In addition to cross-sectional area, other independent risk factors included the interval from last clear fluid intake to surgery and the last oral intake after labor onset.

Antral cross-sectional area ≥487.7 mm ² accurately predicts occult regurgitation in urgent cesarean section under general anesthesia. Incorporating additional risk factors may improve risk stratification.

Chinese Clinical Trial Registry (ChiCTR2400090328).