Luteinized Unruptured Follicles Diagnosed Sonographically

Ovarian sonography provides the only direct non-invasive method for documenting ovulation. Other indirect methods such as serum progesterones, basal body temperature charting, and endometrial biopsies can indicate ovulation when in fact follicular rupture has not occurred by ultrasound evaluation. We refer to the use of ovarian ultrasound in infertility as Ovulation Verification by Ultrasound Methods (O.V.U.M.). The O.V.U.M. approach uses three ultrasound parameters: 1) follicular changes, 2) corpus luteum formation, and 3) secretory endometrium development. The differentiation between proliferative and secretory endometrium has been confirmed by endometrial biopsies.

The system used is a realtime system employing two 3.5 MHz extended focus transducers mounted on a spinning rotor. Serial imaging is initiated immediately after cessation of menstrual flow to rule out pre-existing ovarian pathology. One week later, approximately cycle day 12 or 13, another procedure is performed. If a 1.5 cm or larger follicle is observed daily procedures are initiated until follicular rupture, corpus luteum formation, and/or the appearance of secretory endometrium for two consecutive procedures. If the follicle is unruptured and/or the next cycle is to be monitored with the O.V.U.M. approach, another procedure is conducted after the next menstruation to ascertain resolution of the unruptured follicle and rule out post ovulatory cyst development. During many of the cycles, serum progesterone levels are determined each ultrasound day.

The appearance of secretory endometrium while a follicle persists and/or enlarges with or without hemorrhage realted echogenicity in the presence of increasing postovulatory progesterone levels is indicative of luteinization within the follicle. The cyst or complex mass observed is then a luteinized unruptured follicle. Daily imaging during this part of the cycle is necessary to assure that the follicle did not rupture completely or partially, refill with fluid, and enlarge as a corpus luteum cyst. This has been observed within a 48 hour interval. Therefore a corpus luteum cyst would not be misinterpreted as a luteinized unruptured follicle.

Luteinized unruptured follicles produce a variety of patterns. These patterns can be a continuum from cystic to solid in echogenicity. Four echo patterns have been observed: cystic, complex, septated, and uniform in density equal to or greater than the uterus. The changing accoustical characteristics of aging blood produce these patterns as confirmed by same day ultrasound procedures and laparoscopic follicular aspirations. Most unruptured follicles resolve during one cycle but have remained for up to four cycles.

The illustration demonstrates the development of a luteinized unruptured follicle during days 15 through 19 of the menstrual cycle. Cycle day 15 demonstrated late proliferative endometrium and a 2.3 cm follicle. Day 16, early secretory endometrium and a 3 cm follicles. Day 17, definite secretory endometrium and a 3.4 cm follicle. And day 19, increasing secretory endometrium and a 4.5 cm follicle with hemorrhage. On cycle day 17 the diagnosis of a luteinized unruptured follicle was made.

In conclusion it appears that the diagnosis of luteinized unruptured follicles can be made using the ultrasound parameters described above. Their appearance can represent a multiplicity of echo patterns compatible with benign or malignant pathology including chronic ectopic pregnancies in which a single one-time examination could yield a totally erroneous diagnosis. No pregnancies have occurred in cycles during which these patterns have appeared.