A retrospective review of the histopathological features seen in a series of 4241 endometrial biopsy samples collected from UK Thoroughbred mares over a 25 year period

Abstract

A retrospective review of the histopathological features and the groups in which they are most frequently seen in combination, seen in 4214 endometrial biopsy samples collected from UK Thoroughbred mares over a 25 year period revealed data which supports widely held views on their pathogenesis and significance. Endometrial hypoplasia is most commonly seen in young mares with delayed endometrial maturity. Mononuclear cell infiltrations develop in the endometrial stroma as a reflection of local immune responses to challenge by seminal proteins, micro-organisms, environmental debris and the products of pregnancy, during a brood mare's life. Endometrial hyperplasia most commonly persists during delayed post-partum or post-pregnancy failure of uterine involution, more commonly in younger mares. Glandular degenerative changes and stromal fibrosis develop as an inevitable consequence of ageing, eventually leading to endometrial atrophy, a reflection of gynaecological senility. These degenerative changes result in endometrial incompetence, progressively reducing mares' foaling potentials and increasing their potential for barren years, early pregnancy failures and abortions.