Abstract
There are several different definitions of polycystic ovarian syndrome (PCOS). The most commonly used definition is the Rotterdam criteria, which states that the diagnosis of polycystic ovarian syndrome requires at least two of the following three criteria to be present: (1) oligo- or anovulation, (2) clinical and/or biochemical signs of hyperandrogenism, and (3) polycystic ovaries. The definition requires that all other possible causes of the aforementioned features must be excluded prior to the diagnosis of PCOS being made. Only one of the features required for the diagnosis of PCOS can be diagnosed on ultrasound, and other aetiologies for the required features cannot be excluded by ultrasound. Therefore it is not possible to diagnose a woman as having PCOS by ultrasound alone.
Polycystic Ovaries
There are several different definitions of polycystic ovarian syndrome (PCOS). The most commonly used definition is the Rotterdam criteria, which states that the diagnosis of polycystic ovarian syndrome requires at least two of the following three criteria to be present: (1) oligo- or anovulation, (2) clinical and/or biochemical signs of hyperandrogenism, and (3) polycystic ovaries. The definition requires that all other possible causes of the aforementioned features must be excluded prior to the diagnosis of PCOS being made. Only one of the features required for the diagnosis of PCOS can be diagnosed on ultrasound, and other aetiologies for the required features cannot be excluded by ultrasound. Therefore it is not possible to diagnose a woman as having PCOS by ultrasound alone.
The number of follicles per ovary required to classify ovaries as being polycystic depends on the frequency of the ultrasound transducer being used. If the ultrasound transducer has a frequency of >8 MHz, then identification of 18 or more follicles per ovary is required before the ovaries can be considered polycystic; if the ultrasound transducer has a frequency of <8 MHz, 12 or more follicles per ovary must be identified to meet the criteria.
If a transabdominal approach is indicated (due to the patient being a virgo intacta or not tolerating a transvaginal ultrasound), only the ovarian volume should be reported; the threshold for polycystic ovaries is 10 mL or greater.
Diagnosis of PCOS in adolescent girls should not be based on ultrasound imaging of a high number of ovarian follicles, as there is a high incidence of healthy young women with multifollicular ovaries.
Unstimulated polycystic ovaries are seen with multiple small follicles located around the more dense ovarian stroma.
Figure 6.1 Polycystic ovary without stimulation.
Figure 6.2 Polycystic ovary on day 8 of a stimulated cycle.
Figure 6.3 Polycystic right ovary lateral to the uterus.
(a) Multiple follicles.
(b) Polycystic ovary.
(c) Polycystic ovary.
Figure 6.4 (a-c) Polycystic ovaries, with more than 12 follicles in one slice.
(a) Right ovary, patient with PCO.
(b) Left ovary, same patient as in (a).
Ovarian Cyst
Cysts in the ovary most commonly are the result of ‘mishaps’ during the normal menstrual cycle resulting in follicular or corpus luteum cysts. They are less than 5 cm in diameter and may demonstrate thrombus in the lumen. They usually resolve spontaneously over the next one to two menstrual cycles (Callen, 1994). (Figures 6.6 and 6.7)
Figure 6.6 Thin-walled unilocular ovarian cyst.
