Vaginal cytology in the queen: clinical and cytological correlations

ObjectivesThe aim of this study was to characterise vaginal cytological patterns and standardise its interpretation in female cats. Vaginal cytology has a broadly recognised value for oestrous cycle staging because of the responsiveness of the vaginal epithelium to oestrogens causing changes in the cellular pattern. Unlike the bitch, vaginal cytology is not routinely used in queens.MethodsA total of 39 vaginal smears were collected from 31 intact queens using a simple and quick procedure with little, if any, physical restraint, analysed for cellularity, clearing, epithelial cell types and the presence of red blood cells or neutrophils. Queens were classified in different oestrous phases based on reproductive history and serum progesterone levels.ResultsThe 39 vaginal smears were classified as proestrus (n = 1), oestrus (n = 9), interoestrus (n = 10), dioestrus (n = 9) and anoestrus (n = 9). One vaginal smear was not allocated to any cycle phase because the queen was diagnosed with pyometra. Cellularity was poor in 21/39 smears, from which eight were from queens in oestrus. Cytological oestrus was characterised by 90% or more keratinised epithelial cells, unlike previously reported, and presence of clearing in a scarce to modestly cellular smear.Conclusions and relevanceProgesterone concentration is needed to differentiate interoestrus from dioestrus because of the mixed-cell population on vaginal cytology. Keratinised vaginal cells are consistently found in the anoestrus smears of queens and should not lead clinicians to assume the queen is cycling. Neutrophils can be present in the different oestrous cycles in cats without being associated with clinical signs of disease, unlike red blood cells. These findings demonstrate that vaginal cytology can be a useful tool in feline practice for managing reproductive presenting complaints.