Hypergastrinemia, gastric endocrine cell hyperplasia, and intractable diarrhea. A patient with pernicious anemia developed severe intractable diarrhea night and day. Investigation revealed chronic atrophic gastritis and a markedly elevated level of serum gastrin. No obvious explantation for the diarrhea was found, but after antrectomy, the gastrin level returned to normal and the diarrhea subsided. Possible mechanisms for an association between diarrhea and hypergastrinemia include colonic hypermotility secondary to release of acetylcholine and inhibition of fluid and electrolyte reabsorption within the small bowel. 