The Lag Phase of Gastric Emptying: Clinical, Mathematical and In Vitro Studies

The lag phase of gastric emptying reflects, in large measure, the clinically important milling function of the stomach, but there is little agreement on the best way to acquire, analyze and characterize lag phase data of gastric emptying studies. Twenty normal volunteers were fed a standard 99mTc-sulfur colloid scrambled egg and toast breakfast and imaging data were acquired at 15-min intervals in both anterior and posterior projections with the subject seated. In a significant percentage of the subjects, the stomach count rate rose above the initial count rate, even with geometric mean correction. We attributed the count rate rise to meal self-absorption and conducted mathematical and in vitro experiments, the results of which supported this thesis. Attempts at modeling the data with power exponential fits were unsuccessful in many cases and were complex, nonintuitive and of limited clinical utility. Accordingly, gastric emptying rates were determined by simple linear regression from geometric mean data. The starting index (the time at which the regression line equalled 100%) was calculated to reflect the lag phase. Normal ranges were determined for men and women. Our method of test performance is simple, eliminates confounding variables and provides results with intuitive meaning and with direct clinical relevance.