Ultrasound assessment of the polycystic ovary: international consensus definitions

The polycystic ovary syndrome (PCOS) is a heterogeneous condition, the pathophysiology of which appears to be both multifactorial and polygenic. The definition of the syndrome has been much debated. Key features include menstrual cycle disturbance, hyperandrogenism and obesity. There are many extra-ovarian aspects to the pathophysiology of PCOS, yet ovarian dysfunction is central. At a recent joint ASRM/ESHRE consensus meeting, a refined definition of the PCOS was agreed, encompassing a description of the morphology of the polycystic ovary (PCO). According to the available literature, the criteria fulfilling sufficient specificity and sensitivity to define the PCO should have at least one of the following: either 12 or more follicles measuring 2-9 mm in diameter, or increased ovarian volume (> 10 cm3). If there is a follicle > 10 mm in diameter, the scan should be repeated at a time of ovarian quiescence in order to calculate volume and area. The presence of a single PCO is sufficient to provide the diagnosis. The distribution of follicles and a description of the stroma are not required in the diagnosis. Increased stromal echogenicity and/or stromal volume are specific to PCO, but it has been shown that the measurement of ovarian volume (or area) is a good surrogate for quantification of the stroma in clinical practice. A woman having PCO in the absence of an ovulation disorder or hyperandrogenism ('asymptomatic PCO') should not be considered as having PCOS, until more is known about this situation. Three-dimensional and Doppler ultrasound studies may be useful research tools but are not required in the definition of PCO. This review outlines evidence for the current ultrasound definition of the polycystic ovary and technical specifications.