Predict ovulation in infertile couples by Ultrasonography

What the sonologist sees to predict ovulation?

A small echogenic mass that is thought to represent the cumulus oophorus may sometimes be noted projecting into the follicle. Visualization of the cumulus oophorus has been reported in 80 percent of follicles greater than 17 mm in diameter. Ovulation is reported to be within 36 hours of seeing the cumulus. After the LH surge, the theca tissue becomes hypervascular and edematous and the granulosa cell layer begins to separate from the theca layer. This is appreciated sonographically as a line of decreased reflectivity around the follicle. Within 6 to 10 hours before ovulation, separation and folding of the granu¬losa cell layer produces a crenation or irregularity of the lining of the follicle. This has also been suggested as sign of impending ovulation. Unfortunately, despite the fact that there are a number of sonographic signs that have been described to precede ovulation, there is currently no sonography sign that predicts exactly when ovulation will occur, the signs only give evidence that the time of ovulation is nearing. The mean peak diameter before ovulation reported by Kerin et al was 23.6 + 0.4 mm. However, there are considerable differences in the same.

Hence, the potential signs of impending ovulation are:

• Presence of a dominant follicle (usually more than 16 to 18 mm)
• Anechoic area, double contour, around the follicle (possible ovulation within 24 hrs)
• Separation and folding of the follicle lining (ovulation within 6 to 10 hrs)
• Thickened proliferative endometrium (described later)

How USG confirms that there is ovulation?


Sonography does appear to be very reliable in confirming ovulation once ovulation has occurred. Disappearance of the follicle is noted in 91 percent of cases after ovulation and a decrease in follicle size occurs in another 9 percent. Other signs suggesting that ovulation has occurred are the appearance of cul-de-sac fluid, particularly when it was not present in a previous scan, or the development of intratollicular echoes suggesting the formation of a hemorrhagic corpus luteum.

How anovulation is diagnosed by sonography?


In an anovulatory cycle, ultrasound imaging of the ovaries will reveal either a lack of any follicular development, particularly in the hypogonadotropic hypogonadal patient WHO type I or a few non ovulatory (less than 11 mm) follicles. A dominant follicle larger than 16 mm in diameter will not develop. A cyst may also be associated with anovulation. Anovulation with PCOD will often have enlarged ovaries greater than 8 cm3 in volume with multiple small subcapsular follicles less than 10 mm in diameter. However, normal sized ovaries do not rule out PCOD. Anovulation can be diagnosed when serial scans do not show development of a follicle. A mature corpus luteum is noted sonographically in about 50 percent of patients after ovulation. If pregnancy does not occur the corpus luteum generally degenerates and disappears just before menstruation. Corpus luteum cysts may be 4 to 6 cms in diamter and occasionally even large but are more commonly 2.5 to 3 cms in diameter. They may persist for 4 to 12 weeks and may be responsible for suppressing normal follicular development until they resolve.

This article is also published in India Study Channel