Characteristic of spontaneous intraperitoneal cysts in golden hamsters and European hamsters

Epidemiological study of 340 Golden hamsters and 200 European hamsters bred as laboratory animals and necropsied between 1985 and 1989 in our facility (affiliation 2) revealed high incidence of spontaneous cysts. The incidence was in general higher in European (26 to 62%) than Golden hamsters (0 to 15%). The cysts, of different sizes, were localized first of all in the liver, and secondly (in European hamsters only), in the caecum wall. Light microscopic and electron microscopic examinations showed that the cysts are lined by flattened to cuboidal epithelial cells which, on their surface, have microvilli of different lengths and underneath a continuous basement membrane. These examinations lead further to the interpretation of the liver cysts as cystic distensions of the bile ducts. The cysts in the caecum wall could be interpreted as dilatations of the lymphatic vessels. As to the etiology, which remains unclear, several hypotheses are discussed.