119 ULTRASONOGRAPHIC MONITORING OF CANINE OVARIES CLAMPED AT SUBCUTANEOUS SITE AFTER HORMONE TREATMENT

Abstract

Follicular growth in bitches is usually detected indirectly through behaviour observation, vaginal smears, and hormonal assay in blood. Although real-time ultrasonography can reveal the development of canine ovarian follicles, no method has been established to determine or predict ovulation accurately. Moreover, the location and small size of the ovaries make imaging technically difficult. This study was conducted to investigate follicular waves of canine ovaries stimulated by hormone treatment, in which ovaries had been clamped at a subcutaneous site. Bilateral malacotomy of 3 bitches (4 years of age) at the anestrous (2 bitches) and proestrous (1 bitch) stages of the oestrous cycle was performed using a ventral flank abdominal approach with routine techniques and materials. Each ovary that maintained blood circulation from the suspensory ligament was clamped at a subcutaneous site through muscles of the abdomen. Oestrus was induced using subcutaneous administration of 500 IU of eCG and 1000 IU of hCG (eCG/hCG). Each bitch was given 1000 IU of hCG at 11 days after eCG/hCG administration. Examinations with ovarian ultrasonography using a 7.5-MHz sector transducer, vaginal cytology, and serum progesterone assay were performed daily until 20 days after eCG/hCG administration, and every 10 days thereafter from 20 days to 60 days. Serosanguineous vaginal discharges and vaginal cytology of 2 of the bitches were observed. Follicular growth (>1.1 mm in diameter) was observed in all bitches after eCG/hCG administration. The appearance of new follicular growth was observed on 2 days, 6 days, and 8 days after eCG/hCG administration. The mean diameter of follicles reached 4.3 to 5.5 mm, and the maximum numbers of follicles in bitches were 11 to 16. However, all follicles regressed, irrespective of hCG administration. Elevation in progesterone levels (>2 ng mL^–1) after eCG/hCG administration was observed from 2 days to 12 days after eCG/hCG administration. No correlation was found between follicular development, progesterone profiles, and vaginal smear characteristics. Follicular growth clamped at the subcutaneous site can be monitored easily using ultrasound without an experienced operator. Moreover, ultrasonography proved that hormonal stimulation can induce follicular growth, but the day of appearance of new follicles varied.