An ovary is described to be polycystic when it shows multiple [usually 12] small cystic areas <10 mm in diameter. With transvaginal scan examination better pictures are now available showing the pattern of distribution of the cysts within the ovaries.
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Cysts could be arranged under the capsule giving the classical subcapsular pattern.
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On other occasions cysts might be universally dispersed all over the ovarian stroma.
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Alternatively one ovary could have a universal and the other subcapsular patterns of cyst distribution.
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In up to 6% of patients only one ovary could be polycystic
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As well cysts could be localised to one part of an ovary.
The recent consensus meeting on PCOS held in Rotterdam in 2003 recommended that the pattern of cyst distribution within the ovaries and increased stromal echogenicity to be excluded from the diagnostic criteria. Furthermore they suggested that one ovary showing a polycystic pattern is enough to make the diagnosis in the presence of other diagnostic criteria.
It is important to appreciate that using the combined oral contraceptive pill could affect ovarian morphology and volume masking any polycystic pattern. A dominant follicle or corpus luteum could have a similar effect and patients should usually be scanned during the early follicular phase to guard against this artifact.
The ultrasound pictures shown below demonstrate these different patterns which are not known to have any clinical or endocrinological significance. They all belong to patients who had irregular periods as well as clinical and biochemical hyperandrogenism.
