An evaluation of B-mode and color Doppler ultrasonography for detecting periovulatory events in the bitch.

When determining optimal breeding time in the bitch, specific periovulatory events must be identified. The main objectives were to relate ultrasonographic changes in ovarian blood flow, follicle/corpora lutea count and echotexture to periovulatory events, and to assess the efficacy of each for identifying these events. Twelve Beagle (N = 3), Beagle-cross (N = 2) and hound-cross (N = 7) bitches (body weight range, 7.5-27.5 kg) were examined daily from the onset of proestrus to approximately 4 days post-LH peak. Follicle and corpora lutea count and echotexture analyses were performed using B-mode ultrasound and ovarian blood flow analysis was performed using color Doppler ultrasound. Serum LH concentrations were analyzed by validated RIA. There was an increase (P < 0.05) in ovarian blood flow from the day of the preovulatory LH peak (605 pixels; confidence interval, 397-856), to 1 day after this peak (1092 pixels; confidence interval, 724-1535), enabling detection of the preovulatory LH peak. There were no significant changes in follicle/corpora lutea echotexture relative to days from the preovulatory LH peak. There were significant decreases in follicle/corpora lutea number between Days -1 and 3; Days -1 and 4; and Days 0 and 3, relative to the preovulatory LH peak. We concluded that color Doppler ultrasound performed once daily was more accurate in identifying the preovulatory LH peak than B-mode ultrasound and enabled prospective determination of ovulation.