Absence of luminal intrinsic factor after gastric bypass surgery for morbid obesity.

Abnormally low serum cobalamin levels (less than 180 pg/ml) have been observed in 154 of 429 patients (36%) at an average of 22 months (range 3-64 months) after gastric bypass surgery for morbid obesity. Twenty-four patients underwent a Schilling test and retrograde endoscopy of the bypassed gastric segment to determine the presence of intrinsic factor (IF) in gastric aspirates and in mucosal biopsies at 22 +/- 4 months after surgery. Five patients had a normal cobalamin level (405 +/- 44 pg/ml), and gastric juice intrinsic factor was present in three of them (11 +/- 7 ng/ml). Nineteen patients had a low cobalamin level (113 +/- 8 pg/ml), and gastric juice IF was found in only two subjects of this group (10 ng/ml each). Basal gastric juice IF concentration of healthy control subjects was 24 +/- 5 ng/ml. Schilling test results were normal in all five patients of the first group and in only nine patients of the group with cobalamin deficiency after surgery. To assess whether IF was present within the parietal cells of subjects with absent luminal IF, we studied gastric biopsy material of 14 patients using a well-characterized indirect immunoperoxidase method. IF was identified in fundic mucosal biopsy specimens of all 14 patients with absent gastric juice IF. We conclude that cobalamin deficiency occurs in a significant number of patients after gastric bypass and is associated with absence of gastric juice IF. We propose that this abnormality might be caused by inadequate secretion of IF from the bypassed stomach.