Echotextural changes in the follicular wall during follicle deviation in mares

摘要

The changes detected by ultrasonography in the follicular wall in association with deviation in diameters of Graafian follicles were studied in 8 pony mares. Follicles were examined daily by transrectal ultrasound from 3 days before to 3 days afterthe beginning of deviation (day 0). The following echotextural parameters were recorded: thickness of granulosa, echogenicity of granulosa, prominence of an anechoic layer located beneath the granulosa, and extent of involvement of the circumference of the follicle by the anechoic layer. The mean value for the dominant-follicle for each parameter increased as follicle deviation progressed. The interaction with follicle diameter approached significance for thickness of granulosa and was significant for each of the other 3 end points. The interaction was primarily attributed to lower values in the subordinate follicle on days 2 and 3. The 1st day of an overall echotextural difference between the 2 largest follicles (15.9 ±0.5 days after ovulation) or between days within the largest follicle (16.1±0.5 days) was about 1 day earlier (P<0.05) than the beginning of diameter deviation (17.4±0.8). The effects of follicle diameter versus future follicle status were compared for days -3 to 0 by grouping follicles for each status into 2 diameter categories (16.0-18.9 and 19.0-22.5 mm). Increasing echotextural values for the granulosa (thickness and echogenicity) were attributed to follicle growth; the increasing values for the anechoic layer were attributed to status as a future dominant follicle. It is concluded that development of an anechoic layer beneath the granulosa distinguished the future dominant follicle from the largest future subordinate follicle before the beginning of diameter deviation.