Objective: Endometrial biopsy score is an accepted marker of uterine health and predicted fertility, and it has been suggested that endometrial alternations are correlated with susceptibility to persistent infectious endometritis. The objective of this study was to investigate associations of endometrial biopsy score with: 1) presence of polymorphonuclear cells (PMNs) in the epithelium and stratum compactum in histopathology; 2) presence of PMNs in cytology and 3) presence of infection in microbiology.
Materials and methods: The material for examination was collected from 69 mares suspected for subclinical endometritis (bred three or more times unsuccessfully in the same breeding season) and from 15 maiden mares. Samples were collected by endometrial biopsy and cytobrush technique.
Results: Endometrial alterations (biopsy score IIA, IIB, III) were found in 64 of 82 mares (78%). There was an increase in PMN occurrence for grades IIA, IIB and III. When comparing grades and PMNs infiltration, we observed statistically significant differences between grades I and IIA (p = 0.222) and grades I and IIB (p = 0.042) in samples collected by endometrial biopsy. Statistically significant differences were found in microbiological examination (biopsy p = 0.036; cytobrush p = 0.189), cytological examination (biopsy p = 0.040; cytobrush p = 0.079) and PMN infiltration (p = 0.042) between mares with biopsy scores I and IIB. Furthermore, the highest percentage of infected mares was in grade IIA and IIB, and we found statistically significant differences between grades I and IIA (p = 0.043), and grades I and IIB (p = 0.036) in biopsy samples. We observed a tendency to higher prevalence of endometrial infection in mares with biopsy score IIA, IIB and III than with biopsy score I in samples collected using cytobrush technique. However, there were no statistical significant differences.
Conclusion: Degenerative endometrial changes can predispose to uterine infection and inflammation. Our study shows that mares with endometrial score I are less predisposed to infection than mares with category IIA, IIB and III. Endometrial biopsy is a reliable diagnostic tool.
Keywords: Mare; cytology; endometrial biopsy; endometritis.