Diagnosing PCOS With a Transvaginal Ultrasound

Table of Contents
View All
Table of Contents

Transvaginal ultrasound is one of the main tools a healthcare provider uses to diagnose polycystic ovary syndrome (PCOS). The images found on the ultrasound, in conjunction with the results of blood tests, a thorough patient history, and a physical examination, are used to diagnose this syndrome.

Read on to learn more about the use of transvaginal ultrasounds in diagnosing PCOS.

A gynecologist sets up an ultrasound machine. A transvaginal ultrasound scanner of the internal organs of the pelvis. Female health concept
Kateryna Kukota / Getty Images

Diagnosing Polycystic Ovary Syndrome (PCOS)

Characterized by high levels of androgens, (male hormones like testosterone), polycystic ovary syndrome (PCOS) is an imbalance of sex hormones.

Since these hormones are involved in the regulation of bodily processes ranging from reproduction to metabolism, the condition can lead to a wide variety of signs and symptoms of PCOS.

PCOS Exclusions

The first step when evaluating your symptoms, exam and laboratory findings is to exclude other disorders which might cause these findings. These conditions (which may appear similar to PCOS but are different) include:

Differentiating PCOS from thyroid disease is made more difficult in that some forms of thyroid disease are more common in people with PCOS, and some of the tests used to diagnose thyroid disorders are inaccurate in people with PCOS.

Diagnostic Criteria

The Rotterdam Criteria, the current diagnostic criteria for women with PCOS, state that a woman has PCOS if she has two of the following three criteria (with the exclusion of all other criteria):

  1. Absent or irregular menstrual cycles (eight or fewer periods in one year). Since only two of these three criteria need to be met, there are some women who will meet the criteria for a diagnosis of PCOS despite having regular monthly menstrual cycles.
  2. High androgens on blood work or signs of high androgens in the body such as acne, excessive hair growth (hirsutism), or male pattern hair loss (androgenic alopecia). Blood tests often reveal elevated testosterone and free testosterone levels as well as dehydroepiandrosterone sulfate (DHEAS) levels.
  3. The presence of follicles—commonly referred to as cysts erroneously—on an ultrasound (see clarification below). Some criteria define PCOS as having 12 or more small follicles (that are between two and nine mm in diameter) in both ovaries. However, in the United States, healthcare providers do not typically rely solely on that definition in order to make a diagnosis.

There are many women who have cystic ovaries without symptoms of hyperandrogenism, and many women who have been diagnosed with PCOS who do not have classically "cystic" ovaries.

Recent studies suggest that measuring anti-Mullerian hormone levels may be a useful substitute for transvaginal ultrasound in some cases for the diagnosis of PCOS.

If Your Diagnosis Is Uncertain

If you are uncertain about your diagnosis of PCOS (or lack of one), it can’t hurt to get a second opinion. Endocrinologists and reproductive endocrinologists are medical specialists with additional training in evaluating and treating hormonal disorders.

Check out the American Society for Reproductive Medicine or the Androgen Excess and PCOS Society for a local recommendation.

How Is a Transvaginal Ultrasound Performed?

A transvaginal ultrasound can be performed in a healthcare provider's office. For the procedure, you may be asked to drink up to 42 ounces of fluid before your test to fill your bladder, making it easier to see your ovaries. 

A lubricated ultrasound probe is placed inside the vagina, which transmits an image of the internal organs onto a screen. An ultrasound technician then measures and takes pictures of your ovaries and shares them with yourhealthcare provider. 

Does It Hurt?

Some women may experience very mild discomfort while the technician pushes down during the ultrasound (remember, full bladder!), depending on the ease in which the sonographer can locate the internal reproductive organs.

What Is the Healthcare Provider Looking for on the Ultrasound?

The sonographer will examine your uterus, cervix, and uterus. The number of follicles on your ovary will be counted to yield what is known as an antral follicle count (AFC).

What Are Antral Follicles?

Antral follicles are resting follicles that are found in the ovary at the beginning of each menstrual cycle. They are approximately 2 to 9 millimeters (mm) in size (less than half an inch). A high antral follicle count indicates that a woman has a large number of eggs remaining in her ovary and, in some cases, PCOS.​

Cysts vs. Follicles in PCOS

Both cysts and follicles are more common in women with PCOS than those without the condition. Many confuse cysts with follicles.

Despite its name, women with PCOS don't typically produce cysts, but rather follicles are used as part of the diagnostic criteria.

A name change for PCOS has been proposed to clear up confusion and properly educate health professionals and consumers. 

Women with PCOS tend to produce follicles, which are small collections of fluid in the ovary and are the result, not the cause of, the imbalance of sex hormones. Each month, a woman produces follicles that mature and get released from the ovaries in order to be fertilized.

Because of the hormone imbalance, these follicles don't mature and don't get released by the ovaries, which often leads to infertility.

A Word From Verywell

The diagnosis of PCOS can be time-consuming and frustrating. Other conditions which can cause similar symptoms need to be ruled out first, and then symptoms such as menstrual abnormalities and evidence of androgen excess are evaluated.

Transvaginal ultrasound can provide important information about follicles (as opposed to cysts which has led to much confusion over the years.) The measurement of the anti-Mullerian hormone may provide a substitute for ultrasound in some circumstances.

Once a diagnosis is made, the treatment options for PCOS can be reviewed in order to help you cope with the many annoying (and sometimes serious) consequences of the condition.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Legro RS. Evaluation and treatment of polycystic ovary syndrome Feingold KR, Anawalt B, Boyce A, et al., editors. Endotext. South Dartmouth (MA): MDText.com, Inc.

  2. McCartney CR, Marshall JC. Clinical practice. Polycystic ovary syndromeN Engl J Med. 2016;375(1):54–64. doi:10.1056/NEJMcp1514916

  3. Singla R, Gupta Y, Khemani M, Aggarwal S. Thyroid disorders and polycystic ovary syndrome: An emerging relationshipIndian J Endocrinol Metab. 2015;19(1):25–29. doi:10.4103/2230-8210.146860

  4. Dewailly, D. Diagnostic criteria for PCOS: Is there a need for a rethink?. Best Practice and Research. Clinical Obstetrics and Gynaecology. 2016. 37:5-11. doi:10.1016/j.bpobgyn.2016.03.009

  5. Matsuzaki, T., Munkhzaya, M., Iwasa, T. et al. Relationship between serum anti-Mullerian hormone and clinical parameters in polycystic ovary syndrome. Endocrine Journal. 2017 May 30;64(5):531-541. doi:10.1507/endocrj.EJ16-0501

  6. Bachanek M, Abdalla N, Cendrowski K, Sawicki W. Value of ultrasonography in the diagnosis of polycystic ovary syndrome - literature reviewJ Ultrason. 2015;15(63):410–422. doi:10.15557/JoU.2015.0038

By Nicole Galan, RN
Nicole Galan, RN, is a registered nurse and the author of "The Everything Fertility Book."