Evaluation of ultrasonography for monitoring follicular growth in rhesus monkeys.

The purpose of this study was to determine if the ovaries and uterus of rhesus monkeys could be visualized by ultrasonography and to detect changes associated with follicular growth and ovulation. Animals were examined during 15 menstrual cycles, for an average of nine consecutive days. Ultrasonic recordings were correlated with hormonal parameters (estradiol 17beta, E(2); luteinizing hormone, LH; and progesterone, P) and laparoscopic findings. The uterus and both ovaries were observed in more than 90% of the examinations. A dominant follicle (DF) was identified during all ovulatory cycles, on average 1 d preceding the E(2) peak. The maximal diameter of the DF ranged from 3 to 7 mm. Laparoscopic examinations to determine the site of the DF confirmed ultrasonic findings in 10 of 14 cycles (P < 0.1). There was no significant difference in the size of the dominant and contralateral ovaries; however, more follicles with a diameter of 2 to 7 mm were found on the dominant ovary (P < 0.05). Two animals stimulated with exogenous gonadotropins showed a linear increase in ovarian size for 6 d prior to oocyte recovery (P < 0.05), reflecting an increase in the number of developing follicles. Ultrasonography can be used to identify the DF during spontaneous cycles in rhesus monkeys and to monitor the response of monkeys to exogenous gonadotropins.