The impact of low-volume uterine lavage on endometrial biopsy classification

In the mare, the low-volume uterine lavage technique allows for bacterial sampling of the entire uterine lumen and is usually performed after obtaining the traditional double-guarded endometrial swab for aerobic culture and cytology and before procurement of an endometrial biopsy sample during a breeding soundness examination. The purpose of this study was to explore the potential effects of the low-volume lavage on the endometrial biopsy classification and polymorphonuclear cell (PMNs) infiltration in the context of a breeding soundness examination. Fourteen light horse mares of mixed breed, age 7 to 21 years, with known reproductive history, were included in the study, matched by age and reproductive history, and then divided into treatment and control groups. Transrectal palpation and ultrasonography, endometrial swabbing, and the first endometrial biopsy were performed in all mares. Low-volume uterine lavage was performed in the treatment group but not the control group. After either the lavage or a 15-minute rest, a second endometrial biopsy was obtained from both the control and treatment groups. Endometrial swabs and effluent from the low-volume lavages were submitted for aerobic culture and sensitivity. Biopsy samples were fixed in Bouin's solution for 24 hours, processed, stained with hematoxylin and eosin, and then viewed under bright light microscopy. Additional staining with anti-neutrophil elastase antibody (ab68672) was performed for indirect immunohistochemistry. All samples were interpreted by a blinded observer. When the first (pre-uterine lavage) and second (post-uterine lavage) biopsies were compared using a mixed-effects logistic regression, there was no difference in endometrial biopsy classification (P = 0.74), presence of PMNs in blood vessels (P = 0.728), or infiltration of PMNs in the tissue (P = 0.934) between the treatment and control groups. In this study, the low-volume uterine lavage did not affect the endometrial biopsy classification.