Measurement of gastric emptying by real-time ultrasound

SUMMARY A safe non-invasive technique for the measurement of gastric volume by real-time ultrasound is described. The application of this technique to the measurement of the emptying of liquid from the stomach is outlined. Gastric emptying of liquid was found to be log-linear, the mean half-life of emptying in 10 volunteers being 22.0±2.5 min. Ultrasound measurement of gastric emptying provides an opportunity to study the effects of drugs and disease on gastric motor function in man. The rate of gastric emptying of orally administered drugs is recognised to be of great importance in controlling both the rate of drug absorption, and the peak plasma concentrations that result. The factors that alter gastric emptying rate will in turn influence these parameters. ' Current techniques for the direct assessment of gastric emptying involve the swallow-ing of orogastric tubes or exposure of the subject to ionising radiation.2 There is thus a need for a non-invasive method for the measurement of gastric emptying which is safely repeatable in normal subjects. We have previously described the applica-tion of single beam ultrasound for the measurement of gastric contraction frequency.3 4 We have also outlined a simple but approximate method for the determination of stomach volumes by a hand-held real-time probe.5 Subsequently other workers have also reported the usefulness of real-time ultrasound in recording and measuring gastric contractions.6 We now report the application of real-time ultrasound to enable the accurate and rapid direct measurement of the volume of liquid in the stomach, and the use of this technique to measure the gastric emptying rate of a liquid meal