The effect of small bowel bypass and subsequent resection on gastric acid secretion and serum gastrin

Evaluation of gastric acid secretion and serum gastrin response to proximal or distal intestinal bypass and subsequent resection was undertaken. Ten dogs with gastric fistulas underwent control secretory studies consisting of basal acid output (BAO), maximal vagal stimulation (2 deoxy-d-glucose (2DG) 150 mg/kg iv), maximal histamine stimulation (160 μg/kg/hr iv), and test meal stimuli. Serum gastrin was measured basally and following gastric stimulation. Dogs were then divided into two bypass groups: Group I, distal bypass, leaving 40 cm jejunum and 4 cm ileum; and Group II, proximal bypass, leaving 4 cm jejunum and 40 cm ileum. Postoperatively, repeat studies were performed. Both groups then underwent resection of the bypassed segments followed by repeat secretory and gastrin tests. BAO was significantly increased in Group I dogs. BAO increased from a control of 0.04 ± 0.02 to 0.51 ± 0.19 meq H+/60 min (±SEM). No significant changes in BAO were observed in Group II following bypass. Acid secretion to maximal vagal or maximal histamine stimulation was not significantly different in either group. Serum gastrin response was unchanged in either group following a test meal. In Group I dogs, resection of the previously bypassed bowel produced a further significant increase in BAO (1.44 ± 0.4 meq H+/60 min). After resection of the bypassed bowel, there was no significant change in basal or stimulated gastrin. Gastric fistula BAO increased following 90% distal but not proximal bypass; subsequent resection of the bypassed segment produced a further increase in BAO. Acid secretory responses to both histamine and 2DG were not influenced by either bypass or resection. An increase in BAO without a change in the background of serum gastrin may suggest the presence of a gastric secretory inhibitor in the distal small bowel.