GASTRIC-ACID SECRETION AND VITAMIN-B(12) ABSORPTION AFTER VERTICAL ROUX-EN-Y GASTRIC BYPASS FOR MORBID-OBESITY

Objective This study sought to determine the basal and peak-stimulated acid secretion from the proximal gastric pouch and its relationship to absorption of free and food-bound vitamin B-12 after gastric bypass for morbid obesity. Summary Background Data Gastric bypass can be performed safely and provides acceptable weight loss, but concerns remain about possible long-term complications such as vitamin B-12 malabsorption. The authors hypothesized that by constructing a small pouch of gastric cardia, acid secretion into the pouch would be low, leading to maldigestion of food-bound vitamin B-12 with subsequent malabsorption. Methods Basal and pentagastrin-stimulated peak acid outputs from the proximal gastric pouch were measured in ten patients after vertical Roux-en-Y gastric bypass using a perfused orogastric tube technique. Absorption of free and food-bound Co-57-vitamin B-12 was evaluated separately using 24-hour urinary excretion. Results Basal (mEq/hr, xBAR +/- standard error of the mean [SEM]) and peak-stimulated (mEq/30 min) acid secretions from the proximal gastric pouch were markedly decreased compared to those for age- and sex-matched hospital control subjects (0.01 +/- 0.01 vs. 4.97 +/- 0.66 and 0.08 +/- 0.04 vs. 12.11 +/- 1.34, respectively; p < 0.001 for each). While absorption of free vitamin B-12 was not statistically different from that of control subjects (11 +/- 2 vs. 15 +/- 2%; p > 0.05), absorption of food-bound vitamin B-12 was decreased (0.8 +/- 0.2 vs. 3.7 +/- 0.5%; p < 0.01). Conclusions After vertical Roux-en-Y gastric bypass for morbid obesity, acid secretion is virtually absent and food-bound vitamin B-12 is maldigested and subsequently malabsorbed. The results of this study suggest that postoperative vitamin B-12 supplementation is important and can be achieved with either monthly parenteral vitamin B-12 or daily oral crystalline preparations.