Hyperplasia and Hypertrophy of the Mucosa of Larger Biliary Ducts in Mice Receiving Estrogens. ∗

During the course of observations on mice which had received injections of various estrogens for prolonged periods an enlargement of the bile ducts was observed in many animals. In untreated mice the bile ducts, cystic duct, common duct and its branches, were small thread-like structures. Occasionally a slight cystic distension of the common bile duct was apparent at autopsy. The walls were delicate and when slightly distended almost transparent. Histologically the ducts had a thin and irregular muscularis, and a well-developed mucosa. The tall columnar epithelium was moderately folded on the loose underlying tissue of the lamina propria, and a few small glands extended to the serosa, especially in the common bile duct (Fig. 3).

The bile ducts of many mice which had received estrogens were grossly thickened to several times the size of the ducts of the untreated (Fig. 1). They are also rather rigid, white and somewhat nodular. Enlargement was usually greatest at the points of junction with the branches leading to the several lobes of the liver. The main duct tended to become smaller as it approached the gut. The cystic duct was usually thickened up to the neck of the gall bladder. The gall bladder was involved in only a few mice and in these it was reduced in size and histologically resembled the upper end of the cystic duct.

Microscopic examination of the enlarged ducts of the estrogen-treated mice uniformly showed an extensive increase of the epithelial folds and gland-like processes which completely penetrated the thickened mucosa, the muscularis and frequently projected to the serosa (Fig. 2). The epithelium consisted of tall columnar cells which showed slight mitotic activity. In many ducts 2 types of cells were found, tall cells with an eosinophilic cytoplasm and cells with a clear cytoplasm.