KEY FACTS
Terminology
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Complex heterogenous syndrome of ovulatory dysfunction, menstrual irregularity, and androgen excess
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Rotterdam criteria for polycystic ovarian syndrome (PCOS) developed in 2003: 2 of 3 criteria must be present
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Oligo- or anovulation
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Hyperandrogenism (clinical or biochemical)
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Polycystic ovarian morphology (by US)
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Imaging
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Enlarged ovaries with volume > 10 mL or ≥ 25 follicles per ovary (updated 2014 criteria) measuring 2-9 mm
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> 12 follicles per ovary (2003 Rotterdam criteria) use if US transducer frequency < 8 MHz
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Calculate volume using formula for prolate ellipsoid (longitudinal x transverse x AP diameter x 0.5233)
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Ovarian stromal ↑ echogenicity
Top Differential Diagnoses
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Normal
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Ovarian morphology alone is insufficient for diagnosis of PCOS
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Polycystic ovarian morphology : Seen in ~ 22% of women, whereas PCOS prevalence is only 5-10%
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Suppressed ovary
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Other causes of hyperandrogenism
Clinical Issues
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Anovulation → oligo-/amenorrhea
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Hyperandrogenism → hirsutism
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Obesity with associated hyperinsulinemia/insulin resistance
Scanning Tips
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If dominant follicle (> 10 mm diameter) or corpus luteum seen, repeat scan during next cycle to avoid false elevation of volume
between 2-9 mm in size in a patient with polycystic ovarian syndrome (PCOS). Note the echogenic central stroma 
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