[Sonographic criteria of ovarian function in menstruation cycles].
The sonographic equivalent of the morphological changes of the ovaries in the physiologic menstrual cycle is the periodic evidence of cystic or solid ovarian structures. The selection of the follicle destined for ovulation occurs from a number of many small antral follicles. The initial polymicro follicular reaction the timing of selection differentiates the follicular phase in the selection and in the maturation phase. The selection phase is the limiting temporal part of the cycle. The maturation occurs usually in a unifollicular manner. The daily growth of the dominant follicle (maturation rate) is in most cases not constant. Usually an intraindividual or inter-individual variability of the maturation rate of a mean 2.5 mm per day is present. Preovulatory a non significant delay in the maturation occurs. The sonographic prediction of ovulation is indirect and determined by the timing of selection, the size of the selected follicle, the maturation rate and the size of the preovulatory follicle. The diameter of the dominant preovulatory follicle is 23.1 +/- 2.8 mm. In individual cases solid structures in the preovulatory follicle are recognized which probably correspond to the cumulus oophorus. The corpus luteum structure is significantly larger than the preovulatory follicle with a size of 28.1 +/- 6.7 mm. Corpus luteum cysts can persist until the maturation phase of the next menstrual cycle. The shift from corpus luteum to dominant follicle of the next menstrual cycle can occur alternating between ovaries or homolaterally .