MORPHOLOGIC CHARACTERISTICS OF EQUINE ENDOMETRIUM CLASSIFIED AS KENNEY CATEGORY-I, CATEGORY-II, AND CATEGORY-III, USING LIGHT-ELECTRON-MICROSCOPY AND SCANNING-ELECTRON-MICROSCOPY

Pathologic changes in the endometrium of mares may be rated according to Kenney's method of classification. Category I endometrium contains healthy tissue with no or few widely scattered pathologic changes. At the opposite end, severe widespread pathologic changes are associated with category III. Uterine biopsy specimens were collected aseptically from 16 mares during the estrous and diestrous stages of the cycle. P athologic changes were evaluated, using light microscopy, and endometr ium was classified as Kenney's category I, II, or III. Endometrial tis sue of category I (n = 5 mares in estrus; n = 3 in diestrus); category II (n = 3 in estrus; n = 4 in diestrus), and category VI (n = 4 in es trus; n = 4 in diestrus) were processed for scanning electron microsco py (SEM). All specimens were fixed immediately after biopsy because it was found that numerous bleb-like projections were formed when fixati on was delayed. Category I endometrium had normal glands, and fibrotic tissue was not observed by light microscopy. Scanning electron micros copy revealed numerous hexagonally shaped cells that were covered with many microvilli. Ciliated cells also were observed, and they containe d long healthy cilia. Category II endometrium had 2 to 4 nests surroun ded by collagen fibers. Of the 4 specimens, 3 had moderate leukocyte i nfiltration (59 +/- 14.8 WBC/4 high-power fields [450x]). Scanning ele ctron microscopy revealed some inflammatory changes with slight swelli ng of the cell surface. Several cells in category II endometrium lacke d microvilli, but they were interdispersed among many healthy hexagona l cells. Many nests were seen in category III tissue, and 2 specimens had severe infiltration of WBC (232,264 cells/4 fields). These 2 speci mens appeared to be swollen when examined by SEM. Degenerative changes were more extensive in category III endometrium. Large areas lacked m icrovilli, and some areas had complete loss of the cell boundaries. Nu merous holes and ulcer-like formations also were observed on the surfa ce of this type of endometrium. Morphometric analysis of the ciliated cell population indicated no significant difference in the quantity of cells in normal tissue during estrus vs diestrus. Category III tissue had significantly (P < 0.05) more surface damage than did tissue of t he other 2 categories. In conclusion, the degree of surface damage obs erved, using SEM, paralleled the number of fibrotic nests that were se en by light microscopy. The amount of surface swelling was related to the amount of inflammatory infiltration observed by light microscopy.