Diffuse Uterine Adenomyosis and Bilateral Ovarian Cysts in a Chinchilla Cat

A 10-year-old female intact chinchilla cat was presented with intermittent vomiting and mild lethargy over the previous few months. Clinical signs and laboratory tests were unremarkable. Following an elective ovariohysterectomy, bilateral ovarian cysts and uterine adenomyosis were diagnosed in the patient. Because this cat had a long history of receiving low dose megestrol acetate for estrus suppression throughout her life (1.5 mg/cat, once during estrus, 2-3 times per year), it was suspected that the exogenous progestins increased her risk for disease. To our knowledge, this is the first report in cats demonstrating that even very low doses of megestrol acetate may increase the risk of developing uterine adenomyosis. Furthermore, uterine adenomyosis should be considered in the differential diagnosis of an intact female cat with a long history of unexplained vomiting.