To dynamically measure the gastric volume after ingestion of different foods by ultrasonography, and to investigate the significance of ultrasound examination of gastric emptying time to guide preoperative fasting.

A total of 58 healthy volunteers were prospectively enrolled in Nanhai Division, Guangdong Provincial People’s Hospital, between June 2018 and November 2018 and fasted for 10 h. They were divided into soft beverage group (n=18) , liquid food group (n=16) and solid food group (n=24) , taking 250 ml water, 250 ml whole milk, and 110 g whole-grain bread, respectively. Gastric volume was dynamically detected and evaluated by two-dimensional ultrasound before ingestion, at 10 min, 30 min, 1 h, 2 h, 3 h and 4 h after ingestion. The ultrasound examination for the solid food group was extended to complete gastric emptying.

After 10 h fasting, the gastric emptying was complete. At 10 min after ingestion, the gastric volumes of the clear beverage group, liquid food group and solid food group were 243.92±54.63 ml, 257.31±71.40 ml and 251.30±47.25 ml, respectively (P>0.05) . The emptying time was nearly 1 h for water, nearly 2 h for milk, and nearly 5 h for whole-grain bread (P<0.001) .

Ultrasonography is useful to measure and assess the gastric volume. After ingestion of solid foods, the gastric emptying time is slower compared with water and liquid foods. The emptying time for water and milk is shorter than as the recommended fasting time and therefore has implications in guiding preoperative fasting.

Ultrasound; Gastric contents; Gastric emptying time; Preoperative fasting