The sections below describe the cytologic picture typical of different stages of the canine estrous cycle. Examination of a single smear can sometimes provide useful information, but can also be quite misleading. For example, it is often difficult to differentiate proestrus and diestrus from an isolated smear. It is therefore highly recommended that multiple smears be evaluated.
Anestrus
Intermediate and parabasal cells predominate in smears taken during anestrus. Superficial cells are absent or found in very small numbers. Neutrophils may also be present or absent.