Ultrasonographic interpretation of physiological changes in the female pelvis.

Ultrasonographic assessment of the pelvis of women of child bearing age requires an appreciation of the physiologic changes that occur during the menstrual cycle. A prospective study on 15 women was done between July and December 1981. Pre-ovulatory (late proliferative phase), post-ovulatory (early secretory phase), and premenstrual (late secretory phase) scans were performed during each menstrual cycle. Basal body temperatures were used to determine the time of ovulation. The appearance of the ovaries, uterus, and pouch of Douglas was documented. The purpose of this study was to assess if the developmental stage of a follicle can be determined by observing the presence or absence of ovarian cysts and noting their change with time, to determine if free fluid is an indicator of follicle rupture, and to assess changes in the endometrium. We concluded that one or more small or large ovarian cysts on a single scan is an unreliable predictor of the stage of follicular development; that serial scanning is the preferred method for following physiologic follicular change; that free fluid is associated with ovulation and is commonly seen on post-ovulatory scans; and that while a thick and echogenic endometrium is normal in the premenstrual phase, in most people a more subtle progressive thickening and increased reflectivity is observed.