Rapid intestinal transit as a primary cause of severe chronic diarrhea in patients with amyloidosis.

Objective: The cause of severe diarrhea in patients with systemic amyloidosis is obscure. We therefore performed pathophysiological studies in three such patients in an effort to determine the mechanism of amyloid diarrhea.

Methods: Epithelial cell absorption rate of electrolytes was measured during steady state GI perfusion of a saline-mannitol solution. GI transit time of PEG and absorption of radiolabeled bile acid were measured simultaneously while subjects ingested three meals per day. To obtain a diarrhea control group for transit time and bile acid absorption, normal subjects were studied when they had diarrhea caused by ingestion of Milk of Magnesia (MOM).

Results: Diarrhea could not be explained by malabsorption of ingested nutrients, bacterial overgrowth, bile acid malabsorption, or epithelial cell malabsorption of electrolytes. However, 25% of polyethylene glycol (PEG) ingested with a standard meal was recovered in stool in 45 min, which is 10 times faster than in normal subjects with equally severe diarrhea caused by ingestion of MOM. All of the patients had autonomic neuropathy that remained unrecognized for 15-36 months after onset of chronic diarrhea; it seems likely that this was the cause of rapid transit.

Conclusions: Severe chronic diarrhea in three patients with systemic amyloidosis was mediated by extremely rapid transit of chyme and digestive secretions through the intestine.