Lag phase in solid gastric emptying: comparison of quantification by physiological and mathematical definitions.

Lag phase is considered an important parameter of solid gastric emptying studies. However, different methodologies with their own normal values and physiologic implications are advocated for lag phase measurements. We applied both physiologic and mathematic approaches to quantify lag phases from identical image data sets for direct comparison of these two approaches. Gastric emptying studies were performed on 22 patients using a standard solid meal to calculate the lag phase in each using three different methods: (1) visual analysis to determine time when activity first appeared in the duodenum (LagPh); (2) time-activity curves to determine time of 2% decrease from peak stomach activity (LagCu); and (3) a mathematical definition using the modified power exponential method (TLAG). In addition, time of peak antral activity (AntPk) was calculated. The values for LagPh and LagCu were very similar (mean: 14.6 versus 15.2 min) and correlated well with each other (r = 0.89). TLAG using the power exponential showed different values (mean: 34.7 min) and correlated well only with AntPk (mean: 35.1 min; r = 0.92). We conclude that LagPh and LagCu estimate the time of onset of gastric emptying; the time when the smaller particles in the meal (< 1-2 mm) begin to leave the stomach (onset of variable emptying phase). On the other hand, TLAG and AntPk estimate total trituration time (time for most of meal to be processed) and signal the beginning of the constant gastric emptying phase.