Computer-assisted image analysis of endometrial edema and follicular wall attributes and transrectal follicular tonometry in estrous mare
Date
2002
Authors
Journal Title
Journal ISSN
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Publisher
ORCID
Type
Degree Level
Masters
Abstract
The ability to determine the final stages of follicular maturation and detect
impending ovulation in the mare still eludes veterinarians. The objectives were to
characterize endometrial edema, and follicular wall attributes of the dominant follicle
during the estrous cycle in mares and determine how hormonal manipulation influenced the
outcomes of interest. A computer-assisted image analysis system was used to objectively
evaluate the echotexture oftransrectal ultrasonographic images of the endometrium in the
uterine body, midpoint, and tip of the right and left uterine horns in the mare. Echotexture
was expressed as a computer generated a numeric pixel value (NPV) which reflected the
brightness of the pixel elements within the measurement spot. A novel transrectal
tonometric device was used to measure follicular pressure of the dominant follicle during
estrus. Ten light horse mares were examined during 4 successive estrous periods with
varying degrees of hormonal manipulation (group 1: natural estrus; group 2: prostaglandininduced
estrus; group 3: prostaglandin-induced estrus with hCG administrated when the
dominant follicle was 35 mm in diameter or greater; and group 4: prostaglandin-induced
estrus with hCG administrated when a subjective grade II endometrial edema pattern was
attained). General linear models for repeated measures were used to investigate if there
were differences (p < 0.05) in mean values over time from ovulation. Data were
retrospectively adjusted by hours from ovulation (ovulation = 0 hours). Post-hoc
comparisons between time points were made using the Bonferroni method in SPSS. The
following attributes were evaluated: the mean NPV of the endometrium, mean NPV of the
follicular wall, follicular wall thickness (mean area under the curve) and follicular tonometry (mean pounds per square inch). Mean endometrial NPV in only the uterine body
changed over time from ovulation (p< 0.001) in groups 1, 3, and 4. In all 4 groups, there
was an inverse relationship between the changes in subjective endometrial edema and
endometrial mean NPV in the uterine body. Mean (± SEM) follicular antral diameters
increased until 24 hours before ovulation in groups 1 (p = 0.01), 2 (p = 0.03) and 4 (p =
0.02). Mean antral diameters at time of ovulation for the 4 groups were 45.2 ± 5.5 mm,
46.9 ± 13.5 mm, 39.2 4.1 mm, and 43.0 ± 7.8 mm, respectively. Mean (± SEM) follicular
growth rates for the four groups up to 24 hours before ovulation were: 2.5 ± 0.6 mm/day,
1.9 ± 0.5 mm/day, 1. 7 ± 0.1 mm/day, and 4.0 ± 0.1 mm/day, respectively (p < 0.05). Mean
(± SEM) NPV of the follicular wall increased over time from ovulation for groups 2 (p =0.05), 3 (p < 0.001), and 4 (p = 0.03). The mean (± SEM) daily changes (24 hrs) was 3.1± 1.9 NPV for group 2, 11.7 ± 5.3 NPV for group 3 and 10.7 ± 4.3 NPV for group 4. There
was a progressive increase in the follicular wall thickness in groups 1 (p = 0.005) and 2 (p= 0.01). The mean (± SEM) daily changes (24 hrs) for groups 1 and 2 were 71.3 ± 24.6 pixels and 127.0 ± 45.3 pixels, respectively. Mean (± SEM) intrafollicular pressures
decreased 0.5 to 1.0 PSI between 24 and 12 hrs prior to ovulation (p = 0.01, p = 0.01, p <
0.001, p = 0.03 for groups 1, 2, 3, and 4, respectively). Hormonal treatment shortened the
duration of estrus and accelerated the changes in the attributes evaluated. In conclusion,
computer-assisted image analysis and transrectal tonometry provided a means to
objectively evaluate the normal, morphological changes in the endometrium and the
preovulatory follicle of the mare during the estrous cycle.
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Citation
Degree
Master of Science (M.Sc.)
Department
Large Animal Clinical Sciences
Program
Large Animal Clinical Sciences