Polycystic Ovarian Morphology (PCOM) is a medical term describing a specific appearance of the ovaries seen during an ultrasound examination. It refers to a structural finding rather than a disease itself, which is a distinction many people find confusing. This article explains what PCOM means, how it is identified, and its difference from the more widely known Polycystic Ovary Syndrome (PCOS).
Unpacking the Term Polycystic Ovarian Morphology
The term Polycystic Ovarian Morphology breaks down into three components that describe a physical characteristic of the ovary. “Poly” means many, and “cystic” refers to the small, fluid-filled sacs that are visible on the ovary. These structures are not true cysts, but are actually small, immature ovarian follicles that are arrested at an early stage of growth.
The third part, “morphology,” simply means the form or structure of the ovary. PCOM describes an ovary that has many small, arrested follicles. These ovaries often appear enlarged due to the increased number of follicles and sometimes have a characteristic “string of pearls” appearance on imaging. The presence of PCOM indicates a structural variation in the ovary’s makeup, which may or may not be accompanied by hormonal or metabolic dysfunction.
Diagnostic Criteria and Identification
PCOM is primarily identified through a transvaginal ultrasound, which provides a high-resolution view of the ovaries. Clinicians use this imaging technique to count the number of small follicles and measure the overall size of the ovary to determine if PCOM criteria are met. The specific technical thresholds for PCOM have been updated over time to improve accuracy.
Current international guidelines define PCOM as having 20 or more small follicles, typically measuring 2–9 mm in diameter, in at least one ovary. Alternatively, PCOM can be diagnosed if the ovarian volume is measured at 10 milliliters (mL) or greater. It is important that the ultrasound is performed when the ovaries are “quiescent,” meaning there is no dominant follicle or corpus luteum present, which would skew the size measurements.
PCOM Versus the Polycystic Ovary Syndrome
The distinction between PCOM and Polycystic Ovary Syndrome (PCOS) is a frequent source of confusion, but the two terms are not interchangeable. PCOM is a descriptive finding on an ultrasound, while PCOS is a complex endocrine and metabolic syndrome. The diagnosis of PCOS typically relies on the widely accepted Rotterdam criteria, which require a woman to exhibit at least two out of three specific characteristics.
These three criteria are: oligo- or anovulation (irregular or absent menstrual periods), clinical or biochemical hyperandrogenism (signs of excess male hormones like acne or hirsutism, or elevated androgen levels in the blood), and PCOM on ultrasound. Therefore, a woman can have PCOM and still not have PCOS if she does not have the other two features. The presence of PCOM alone is simply one of the potential components of the syndrome.
A woman with PCOM but normal cycles and hormone levels is not considered to have the syndrome. When a diagnosis of PCOS is confirmed using these criteria, it is classified with the ICD-10 code E28.2. This code is used for medical record-keeping and billing.
Implications of PCOM Without PCOS
For individuals who have PCOM on ultrasound but do not meet the criteria for PCOS, the finding is often considered a normal variation of ovarian anatomy. This isolated finding is quite common, with estimates suggesting that PCOM is present in up to 25% of healthy women of reproductive age who have regular menstrual cycles. In these cases, the PCOM is typically asymptomatic and does not require medical intervention.
The presence of isolated PCOM may have some mild clinical relevance. Due to the high number of immature follicles, these women have an increased follicular pool, which might slightly increase their ovarian reserve. This increased reserve can sometimes lead to minor challenges with fertility, but it does not automatically translate into infertility, as ovulation is usually regular. Having PCOM alone does not strongly predict the later development of PCOS.