Gastric emptying of a solid meal starts during meal ingestion: combined study using 13C-octanoic acid breath test and Doppler ultrasonography. Absence of a lag phase in 13C-octanoic acid breath test.

Scintigraphy and the 13C-octanoic acid breath test are both applied to assess gastric emptying. Using the 13C-octanoic acid breath test, excretion curves show 13C excretion immediately after ingestion of a solid egg meal, in contrast with scintigraphy where gastric emptying is observed after a lag phase. The aim of our study was to investigate whether transpyloric flow occurs during and directly after meal ingestion. Therefore, transpyloric flow was measured during and after ingestion of an egg meal labeled with 13C-octanoic acid, using Doppler ultrasonography. The breath test was performed simultaneously, with samples taken at regular intervals. The first emptying episode was observed 6.9 (3.9-16.2) min after start of meal ingestion. A significant relation between recovery of 13C and total duration of gastric emptying during the first 20 min was observed (partial correlation coefficient r = 0.80, p < 0.001). In conclusion, transpyloric flow starts during ingestion of a solid egg meal and results in detectable excretion of 13C.