Surgical translocation and ultrasound bio-microscopy of the ovaries in rabbits

Experiments were designed to validate the use of ultrasound bio-microscopy (UBM) as a method for assessing ovarian structures in rabbits. In Experiment 1, female New Zealand White (NZW) rabbits (n=4) were given an ovulation-inducing treatment and the ovaries were examined ex situ by UBM using a 25 MHz oscillating sector transducer before being processed for histology. Pairwise correlations revealed strong relationships between UBM and histology in the number (Mean±SEM) of follicles ≥0.6 mm (17.3±2.3 compared with19.0±1.6, respectively; r=0.96; P=0.040), CL (8.5±2.9 compared with 8.8±3.0; r=0.99; P=0.003), the diameter of follicles (1.1±0.05 compared with 1.1±0.03 mm; r=0.96; P=0.035) and CL (2.1±0.7 compared with 1.8±0.6 mm, r=0.99; P<0.001). In Experiment 2, the ovaries of NZW rabbits (n=12) were surgically translocated to a subcutaneous position in the flank region to permit serial examination of ovarian structures in vivo by UBM. Beginning 2 weeks after surgery, the ovaries were examined by UBM daily for at least 18 days, and again 2 months after surgery. Post-operative complications were minor, and both ovaries of each rabbit were identified consistently. The number and diameter of follicles ≥0.6 mm were readily visualized during each examination. Multiple corpora lutea were detected in two rabbits, and serial follicular and luteal dynamics in these two rabbits were used to document the consistency of UBM and the retention of ovarian function after surgery. It is concluded that UBM is a valid tool for instant assessment of rabbit ovarian structures (follicles, corpora lutea, and cumulus-oocyte complexes) ex situ, and for serial assessment in vivo using a transcutaneous approach. Surgical translocation had no apparent untoward effect on ovarian function.