LAG PHASE IN SOLID GASTRIC-EMPTYING - COMPARISON OF QUANTIFICATION BYPHYSIOLOGICAL AND MATHEMATICAL DEFINITIONS

Lag phase is considered an important parameter of solid gastric emptyi ng studies. However, different methodologies with their own normal val ues and physiologic implications are advocated for lag phase measureme nts. We applied both physiologic and mathematic approaches to quantify lag phases from identical image data sets for direct comparison of th ese two approaches. Gastric emptying studies were performed on 22 pati ents using a standard solid meal to calculate the lag phase in each us ing three different methods: (1) visual analysis to determine time whe n activity first appeared in the duodenum (LagPh); (2) time-activity c urves to determine time of 2% decrease from peak stomach activity (Lag Cu); and (3) a mathematical definition using the modified power expone ntial method (TLAG). In addition, time of peak antral activity (AntPk) was calculated. The values for LagPh and LagCu were very similar (mea n: 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 gastri c emptying; the time when the smaller particles in the meal (< 1 -2 mm ) begin to leave the stomach (onset of variable emptying phase). On th e other hand, TLAG and AntPk estimate total trituration time (time for most of meal to be processed) and signal the beginning of the constan t gastric emptying phase.