Histopathologic findings in uterine biopsy samples from subfertile bitches: 399 cases (1990-2005)

Objective-To determine the prevalence of various lesion types detected by histologic evaluation of uterine biopsy samples collected from subfertile bitches. Design-Retrospective case series. Animals-399 sexually intact bitches. Procedures-Results of histologic evaluation of canine uterine biopsy samples submitted by a single veterinary practice and clinical histories of dogs from which samples were obtained were reviewed. Clinical data including age, reason for biopsy, and histopathologic findings were recorded. The prevalence of specific lesions was determined, categorized by severity and age, and statistically analyzed. Results-Endometritis (170/399 [42.6%] cases) and cystic endometrial changes, including cystic endometrial hyperplasia (133/399 [33.3%]) were the most prevalent lesions in the study population. Eighty-nine of 170 (52.4%) cases of endometritis were characterized as chronic with predominantly lymphocytic or lymphoplasmacytic inflammatory infiltrates, 51(30.0%) included mixed inflammatory reactions, and 30 (17.6%) were characterized as having acute inflammation with neutrophils, eosinophils, or both. Fibrosis was common (101/399 [25.3%] cases). Eosinophilic endometritis was significantly associated with a history of fetal loss during the same breeding cycle. No significant difference was found in prevalence of lesions among age groups. Conclusions and Clinical Relevance-The high prevalence of endometritis in this population of dogs suggested that acute and chronic endometritis may be related to subfertility in bitches. The association of eosinophilic endometrial infiltrates with a history of fetal loss may be an important diagnostic finding in dogs with endometritis.