What is the role of ovarian ultrasound in diagnosing Polycystic Ovary Syndrome (PCOS)?

From the Guidelines

The role of ovarian ultrasound in diagnosing Polycystic Ovary Syndrome (PCOS) is limited, and it should not be used as a standalone diagnostic tool, but rather as one of the three Rotterdam criteria, which also include oligo- or anovulation and clinical or biochemical signs of hyperandrogenism 1. When using ultrasound to diagnose PCOS, the presence of 20 or more follicles measuring 2-9 mm in diameter in at least one ovary, or an ovarian volume greater than 10 ml, is considered indicative of polycystic ovarian morphology (PCOM) 1. Some key points to consider when using ultrasound to diagnose PCOS include:

• The transvaginal ultrasound approach is preferred, if acceptable to the individual being assessed 1
• The threshold for PCOM should be revised regularly with advancing ultrasound technology, and age-specific cut-off values for PCOM should be defined 1
• Ultrasound should not be used for the diagnosis of PCOS in those with a gynaecological age of < 8 years (< 8 years after menarche), due to the high incidence of multi-follicular ovaries in this life stage 1
• Clear protocols are recommended for reporting follicle number per ovary and ovarian volume on ultrasound, including last menstrual period, transducer bandwidth frequency, approach/route assessed, and total follicle number per ovary measuring 2-9mm 1 It's also important to note that the diagnostic accuracy of ultrasonographic markers in PCOS diagnosis can vary depending on factors such as age, BMI, and transducer frequency 1. Overall, while ovarian ultrasound can be a useful tool in diagnosing PCOS, it should be used in conjunction with clinical symptoms and hormonal tests to ensure a comprehensive diagnosis.

From the Research

Role of Ovarian Ultrasound in Diagnosing PCOS

The role of ovarian ultrasound in diagnosing Polycystic Ovary Syndrome (PCOS) is a crucial one, as it helps in identifying polycystic ovarian morphology (PCOM), which is one of the key features of PCOS.

• Ovarian ultrasound is used to assess the number of follicles in the ovary and the ovarian volume, which are important criteria for diagnosing PCOS 2, 3, 4, 5, 6.
• The Rotterdam consensus in 2003 defined the polycystic ovary as having 12 or more follicles, measuring between 2 and 9 mm, and/or an ovarian volume >10 cm3 3.
• However, more recent studies have suggested that these criteria may not be sufficient to distinguish between women with PCOS and healthy women, and that a higher threshold of follicle counts may be needed 4, 6.
• A study published in 2013 found that a threshold of 26 follicles throughout the entire ovary was required to distinguish between women with PCOS and healthy women 6.
• Another study published in 2011 found that a serum Anti-Müllerian hormone (AMH) level >35 pmol/l (or >5 ng/ml) was more sensitive and specific than a follicle count >19 for defining PCOM 2.

Ultrasound Criteria for PCOS

The ultrasound criteria for PCOS have been updated in recent years to reflect advancements in imaging technology and reliable methods for estimating follicle populations.

• The updated criteria include a higher threshold of follicle counts, such as 26 follicles throughout the entire ovary, to distinguish between women with PCOS and healthy women 6.
• The use of transvaginal ultrasonography and a reliable grid system approach to count follicles has been recommended to improve the accuracy of follicle counts 6.
• The assessment of ovarian volume and follicle counts in a single cross section has also been found to have diagnostic potential for PCOS, although to a lesser extent than follicle counts throughout the entire ovary 6.

Limitations and Future Directions

While ovarian ultrasound is a valuable tool in diagnosing PCOS, there are limitations to its use, including the need for standardization of the follicle counting technique and the need for regularly updating the thresholds used to define follicle excess.

• Further research is needed to establish commonly accepted diagnostic norms concerning the number of ovarian follicles and the standardization of the technique in which they are counted 5.
• The use of serum AMH levels as a surrogate marker for PCOM is a promising area of research, although full standardization of AMH assays is needed before they can be routinely used for clinical practice and research 2, 4.