Serum vitamin B12 concentration after proximal gastric vagotomy.

The serum concentration of vitamin B12, blood hemoglobin, and gastric acid secretion capacity was studied preoperatively and 1 and 5 years after proximal gastric vagotomy (PGV) in 15 patients. There was a significant reduction in the mean concentration of vitamin B12 at 1 year, but this disappeared within 5 years after PGV. The serum concentration of vitamin B12, however, remained at all times within the health-related reference interval. The blood hemoglobin concentration was unaltered during the follow-up period. The decrease in gastric acid secretion capacity gained by PGV was permanent, and no tendency to increased acidity was observed during the 5-year period. The temporary decrease in serum concentration of vitamin B12 reflects a PGV-induced diminished production of intrinsic factor in the parietal cells. In the characterization of parietal cell function the determination of serum vitamin B12 concentration is, however, much less sensitive than gastric acid secretion tests. The observed change in vitamin B12 concentration after PGV was subclinical, self-corrected, and thus required no treatment.