Gastrointestinal pH, Motility Patterns, and Transit Times After Roux-en-Y Gastric Bypass

Background Studies investigating the underlying pathophysiology are needed to help explain and understand the postoperative complications following Roux-en-Y gastric bypass (RYGB) surgery. This study aimed to characterize segmental gastrointestinal pH profiles, motility measures, and transit times in patients with RYGB. Materials and Methods Nineteen patients with RYGB underwent a standardized wireless motility capsule assessment. The orocecal segment was defined from capsule ingestion until the passage of the ileocecal junction. Segmental median pH, motility index, and transit time were determined for the oro-cecal and colonic segment as well as for the first and last hour of both these segments. For comparison to reference values, data from 17 healthy age- and gender-matched controls was used. A mixed effect model was used to describe differences between groups. Results Median pH was high in patients with RYGB during the first hour of the oro-cecal segment (6.45 +/- 0.4 vs 3.65 +/- 1.55 pH units for healthy controls; P < 0.001), as well as during the entire oro-cecal segment (6.97 +/- 0.4 vs 5.51 +/- 1.1 pH units; P < 0.001). The same was evident for the median motility index (152 +/- 64 vs 35.8 +/- 31.1 mmHg*sec/ min; P < 0.001 and 130 +/- 65.9 vs 89.1 +/- 20 mmHg*sec/min; P < 0.012, respectively). Median motility index was low the first hour of the colon (55.2 +/- 45.7 vs 122 +/- 77.9 mmHg*sec/min; P < 0.002). Additionally, patients had short oro-cecal transit time (5.8 +/- 1.6 vs 7.6 +/- 1.4 h; P < 0.001) and long colonic transit time (29.4 +/- 17.5 vs 19.6 +/- 12.2 h; P = 0.048). Conclusions In patients with RYGB, the oro-cecal segment was characterized by an alkaline intraluminal environment, high motility activity, and short transit time. In contrast, colonic transit time was long.

Automated summary

This study found that in patients with RYGB, the gastric pH was high, motility index was high, and transit time was short, while the colonic transit time was long.