The ultrasound examination also allowed for the
verification of size and persistence of follicles which were
used as criteria to diagnose cysts. Anaechoic structures
with thin, smooth walls and a diameter larger than 12 mm
were considered to be cysts (MacLachlan and Foley, 1996).
In females with cysts ultrasonography was continued until
the fifth day after estrus onset to confirm the persistence of
cysts.