Canine pyometra – an update and revision of diagnostic terminology

Pyometra is frequently diagnosed in the female dogs, and it is characterized by endometrial inflammation, accumulation of purulent exudate within the lumen, and bacterial infection. In the dog, pyometra affects more often aged nulliparous bitches during the luteal phase. Pathogenesis of pyometra is multifactorial and progesterone seems to be a key factor. Cystic endometrial hyperplasia has been described as a predisposing condition for canine pyometra. However, a recent study demonstrated that cystic endometrial hyperplasia is not significantly associated with naturally occurring pyometra, whereas there is a significant association of this condition with pseudoplacentational endometrial hyperplasia. The aim of this review is to provide an update on canine pyometra, with focus on its association with uterine hyperplasic lesions, which supports a proposal for adoption of more adequate diagnostic terminology.