[The pathogenesis of the "endometritis-pyometra complex" in the female dog]

Based on investigations in 51 bitches (uteri and ovaries after ovariohysterectomy), suffering from "endometritis-pyometra-complex" (without, n = 38; with, n = 13, hormonal pretreatment), morphologic-functional endometrial characteristics (light microscopy, scanning electron microscopy, enzyme histochemistry, immunohistochemical estrogen receptor analysis) are correlated with ovarian findings, plasma estradiol and progesterone levels as well as microbiological results. The estrous phase of all cycling patients was determined as "diestrus". Plasma estradiol and progesterone concentrations fluctuate within physiological variations. In all cases, not including those, pretreated with progestagen, histological signs of irregular hyperproliferation of uterine glands are obvious, closely related with enzyme histochemical aberrations and atypical endometrial estrogen receptor state. This is interpreted as indicative for prolonged periestrous estrogen induced effects, undergoing different stages of secretory transformation due to the species specific long lasting corpus luteum period. A comparable pathogenesis is supposed deriving from estrogen applications (e. a. after mismating) due to intensified hormonal stimulation and sensibilization of the endometrium, predisposing to ascendant infections by facultative pathogenic bacteria (e. a. E. coli, Streptococcus sp.). Patients without ovarian cyclicity, resulting from progestagen application, exhibit findings, that indicate hormonal imbalances: secretory hypertrophy, irregular regeneration, fibrous atrophy and rigid secretion, resembling those possibly occurring in women after long administration of oral contraceptives.