The study was performed on 45 bitches in different cycle phases that were divided into the following groups: anoestrus (I, n=15), heat (pro-oestrus (n=7) or estrous (n=8) (II, n=15) and metestrus (III, n=15). Moreover, all experimental dogs were grouped according to their age: younger than 5 years (Y, n=35) and older than 5 years (O, n=10). The endometrial status was evaluated using cytological, bacteriological and biopsy samples obtained after ovariohyster- ectomy.

The main uterine pathology diagnosed by biopsy was endometritis, since 40%–66% of bitches, independent of the experimental group, developed this condition. No significant differences were found among the cycle phase groups (p>0.05). By contrast, significant differences were found in the age groups; the prevalence of this pathology was higher in older bitches (p=0.0019). The general prevalence of cystic endometrial hyperplasia (CEH) and a normal endometrium (NE) was lower (6.7–26.7% vs 26.7–53.3%) in all groups, and no statistically significant differences were found between certain groups (p>0.05). The percentage of polymorphonuclear neutrophilic leukocytes (PMNs) in endometrial cytology was generally low (< 2%) and did not differ signifi- cantly among the experimental groups (p=0.142). In general, a low degree of correlation was found between the diagnostic results by endometrial cytology and biopsy (Kappa Coeffi- cient=0.046). Positive bacteriological findings were found in approximately 50% of the bitches, independent of the cycle phase and health status of the endometrium. No correlation was found between the bacteriological and histopathological findings (p=0.883).

In conclusion, uterine cytology is not a reliable diagnostic method to detect the subclinical inflammatory and degenerative uterine pathologies in cyclic bitches.