Pancreatic pathology, chemically defined liquid diets and bacterial flora in the rat.

Germfree and conventional rats on a completely defined liquid diet from weaning to adult life developed pancreatic lesions. In the germfree animals they were reversible and disappeared in the majority of this group after 5-8½ months. The lesions were encountered after ingestion of the diet for 1 month and consisted of acinar atrophy with fibrosis. The latter was largely replaced by stromal fat after 3½ months in the more vulnerable conventional rats. From 4 months of diet ingestion onward unusual focal metaplasia was observed in the pancreas of conventional animals. The metaplastic cells resembled hepatic or oxyphilic (oncocytic) epithelium and were believed to arise in the islets but the possibility of acinar or ductal origin could not be eliminated.