Problems associated with ultrasonography of the canine ovary around the time of ovulation.

Real-time B-mode ultrasound imaging was carried out, using a scanner of moderate quality, on 40 fresh bitch cadavers to identify the presence of ovaries and significant ovarian structures. The results indicated that accurate identification of the ovaries depended on the presence of significant follicles or corpora lutea (CL). The findings were verified at post-mortem examination. The study was continued by scanning 35 live bitches using three different scanning units of increasingly improved quality to show that the process of ovulation could be assessed with reasonable accuracy with improved quality of equipment, although the exact fate of the follicle could not be imaged. The results were judged against assays for blood circulating progesterone. A final group of seven live bitches were scanned with a high-grade scanner using an annular phased-array transducer to attempt to image the process of ovulation. The non-echogenic follicle disappeared and was replaced by the CL that was hypoechoic with respect to surrounding tissue, thus allowing accurate assessment of the time of ovulation. This was confirmed by progesterone assay.