Ovulation and corpus luteum formation observed by ultrasonography

Ultrasonic observation of the ovary at 8–12 hr intervals reveals typical appearances when ovulation has take place. Shortly after ovulation there is an increase in solid echoes as the cystic follicle decreases in size until a small, less intense echogenic area (“cystic or structural loosening”) stays visible within the ovary. This either stays unchanged during the luteal phase or increases up to a cystic corpus luteum. Premensturally, the ovary regains its more homogenous solid structure. When cystic alteration has taken place, solid echoes invade the cystic corpus luteum which continuously decreases in size once menstruation has started. A cystic structure, similar to a cystic corpus luteum, in the second part of the menstrual cycle possibly signifies luteinisation of the unruptured follicle when no collapse of the follicle is observed before. After multifollicular development, the collapse of the predominant follicle may be difficult to outline when, simultaneous to ovulation, other follicles enlarge as in patients treated with gonadotrophins.