Histological changes in the uterine and ovarian walls in pyometra

In recent years, the number of small domestic animals, which have become cohabitants of people both in cities and in rural areas, has increased significantly. Keeping cats indoors with the use of artificial lighting has led to the fact that anestrus falls out of their sexual cycle, and the stages of arousal are manifested in them throughout the year. This phenomenon is the cause of various inflammatory processes in the uterus. The most common gynecological diseases in cats are pyometra, endometritis, and vaginitis. Violation of the hormonal status in the hypothalamus-pituitary chain in the absence of contact with natural partners is accompanied by a disorder of the function of the ovaries and uterus. A change in the hormonal balance, manifested by a violation of the ratio of estradiol and progesterone concentrations in the blood, affects the function of the endometrium and provokes an increase in the secretory activity of the uterine glands. Initiated in the arousal stage of the sexual cycle, it does not fade away but progresses even more. This is how the conditions for the emergence of an inflammatory process in the uterus are created and maintained. The course of the disease is accompanied by persistent morphological changes in the state of the uterus and all organs and their systems. Diagnosis of the disease is well-developed and does not present any difficulties in veterinary clinical practice. However, the approaches to substantiating the etiology and pathogenesis of the disease and the effectiveness and expediency of a conservative or operative treatment method are controversial. There are also limited reports on the histostructure of certain areas of the fallopian tubes and uterus, depending on the functional state of the cat’s body. The research aimed to investigate the histological structure of the uterus and ovaries of cats with pyometra. Ten explanted uteri and ovaries were subjected to histological examination in 10 cases of surgical treatment of cats with pyometra. In this research, it has been established that the pathohistological changes of the uterine wall due to pyometra are characterized by endometrial hypertrophy, the basis of which is hyperplasia with the formation of various forms of outgrowths covered with epithelium, followed by their dystrophy and the formation of detritus, which locally sticks to the endometrium and fills the uterine cavity, local desquamation of the serous mesothelium membrane, compaction of the muscular membrane, loosening of the vascular membrane, and dilatation of veins. The surface parts of the endometrial glands undergo dystrophic changes and cystic degeneration, manifested by hyperplasia of their walls and the formation of cavities filled with detritus of desquamated epithelium and cavities of “empty cysts” filled with remnants of detritus. Deep sections of the endometrial glands are reduced, but their histostructure is not transformed. Changes in the ovaries are manifested by focal desquamation of the mesothelium, the formation in the depth of the cortical substance of mainly one voluminous corpus luteum, atresia of follicles, and the presence of full-fledged tertiary follicles.