Polycystic ovaries

Radswiki et al.

Polycystic ovaries (PCO) is an imaging descriptor of a particular type of change in ovarian morphology. A proportion of women with polycystic ovaries will have the polycystic ovarian syndrome (PCOS), which in turn requires additional clinical as well as biochemical criteria. Otherwise PCO can be considered a normal variant. 

PCO may be seen in ~20% women of reproductive age 1,4.

Ultrasound

Transvaginal ultrasound is considered the gold standard in the diagnosis of polycystic ovaries. Features can affect either one (unilateral polycystic ovary) or both ovaries.

Features include:

  • presence of >25 follicles per ovary (superseding the earlier Rotterdam criteria of 12 or more follicles) 
  • individual follicles are generally similar in size and measure 2-9 mm in diameter 7
  • peripheral distribution of follicles; this can give a "string of pearls" appearance
  • background ovarian enlargement (volume greater than 10 cc) 7
  • central stromal brightness +/- prominence

Only one ovary fitting these criteria is sufficient to define PCO. If there is evidence of a dominant follicle (>10 mm) or a corpus luteum, the scan should be repeated during the next cycle 9.

A study published in 2013 suggested that the number of follicles in each ovary- FNPO (follicle number per ovary) is a more sensitive and specific criteria for diagnosis of the PCO compared with numbers of follicles in cross section-FNPS (follicle number per section) or ovarian volume- OV. This study showed an FNPO threshold of 26 follicles had sensitivity of 85% and specificity of 94% when discriminating between controls and PCOS. A FNPS threshold of nine follicles had a 69% sensitivity and 90% specificity, and an OV of 10 cm3 had a 81% sensitivity and 84% specificity 11.

MRI

Pelvic MRI may show most or all of the above sonographic features. Signal characteristics include:

  • T1: the small uniform follicles are low in signal while the central stroma is of intermediate signal (e.g. compared with normal myometrium)
  • T2: follicles have high T2 signal while the central stroma is of comparatively low T2 signal 8

General imaging differential considerations include:

  • multifollicular ovaries (MFO): fewer cysts (~ 6 or more per ovary), which tend to be larger (up to 10 mm in diameter) and distributed throughout the ovary with no stromal hypertrophy 2
  • with a lack of consensus sometimes it is easier to report the number of follicles in each ovary rather than attempt to label the ovaries as "polycystic" or "multifollicular"
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Article Information

rID: 14971
System: Gynaecology
Section: Pathology
Synonyms or Alternate Spellings:
  • PCO
  • Polycystic ovaries (PCO)

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