Background

Weight loss success after gastric bypass (GB) is commonly attributed to stomach size and ileal hormone stimulation (i.e.GLP-1,PYY). Inherent to these factors is nutrient transit. Remarkably, there are no reference ranges for proper gastric emptying (GE) or small bowel transit (SBT) times after GB. The objective of this study was to identify GE and SBT times in subjects with failed and successful weight loss response after GB.

Methods

Subjects with failed weight loss response (excess body weight loss;EBWL<40%) and successful response (EBWL>60%) at least 18-months after GB underwent six hour GE and SBT scintigraphy with standardized semi-solid meal to identify the following time points: GE 10% (TG10%) and 50% (TG50%), Intestinal Max (TIntMax), Duodenal-Ileum transit (TDI-transit), Ileum 10% (TIleum10%), Cecal Filling Initiation (TCecalFilling) and Ileocecal Valve transit (TICV-transit). Values are reported as minutes; median[range] for GE, mean±SD for SBT.

Results

30 subjects with failed response (mean EBWL=22±13%) and 10 with successful response (mean EBWL=70±12%) were studied. Scintigraphy findings were as follows: TG10%=1 min [all subjects]; NS, TG50%=1 vs. 1 min [1-150]; NS, TIntMax=143±80 vs. 63±55 min; p=0.002, TIleum10%=214±85 vs. 119±70 min; p=0.002, TDI-transit=212 ± 87 vs. 118±70 min; p=0.002, TICV-transit=36±16 vs. 39±27; p=0.744, TCecalFill=244±158 vs. 158±77; p=0.008.

Conclusions

Subjects with failed weight loss response to GB had an approximate 2-3 times prolonged transit time from jejunum to ileum. No significant differences were identified in GE or amount of time nutrient resided in ileum. These findings implicate the importance of mid-bowel transit to the metabolic response observed after GB.