PCOS ultrasound vs Normal ultrasound: What’s the difference?

Polycystic ovary syndrome (PCOS) is a common endocrine condition among reproductive-age women. There is no single test to detect or diagnose this condition. However, an ultrasound is one of the most helpful tools that can find the clues. Let’s find out what kind of ultrasound is performed to detect PCOS, the difference between normal ovary ultrasound vs PCOS ultrasound, and what PCOS looks like on ultrasound.

What is PCOS ultrasound vs normal ultrasound?

An ultrasound is a relatively easy and available option to examine signs of PCOS. This procedure is considered less invasive than hormonal assessment; however, an ultrasound alone is usually not enough for diagnosing. PCOS ultrasound and normal ultrasound vary both in techniques and results. 

Generally, there are three types of ultrasounds:

• External transabdominal ultrasound (TAS) – a traditional abdominal ultrasound performed on the surface of a belly;
• Internal transvaginal ultrasound (TVS) – a scan instrument that looks like a wand (transducer). It uses high-frequency sound waves to visualize internal reproductive organs (cervix, uterus, fallopian tubes, and ovaries).
• Transrectal ultrasound (TRS) – a scan that is used to look for abnormalities in the rectum and area around. 

Transabdominal ultrasound

This type of ultrasound is used for organs and tissues that can be checked through the skin. Transabdominal ultrasound can check stomach, kidneys, etc.

Transvaginal ultrasound

A transvaginal ultrasound (TVS) allows a doctor to identify:

• Tumors;
• Fibroids;
• Polyps;
• Cysts;
• Signs of cancer;
• Signs of ectopic pregnancy or miscarriage;
• Potential causes of fertility issues;
• Signs of a pelvic infection;
• Position of an intrauterine device (IUD).

This transvaginal ultrasound (TVS) is used to examine potential signs of PCOS. The results of the TVS ultrasound are processed with specific software tools and converted to an image called a sonogram. A health care provider will analyze this sonogram to detect possible issues in the organs. The procedure is not painful, however, might be somewhat discomforting, and usually lasts anywhere from 15 minutes to an hour.

Transrectal ultrasound

In certain cases, for example, when a female hasn’t started her sexual life, a transrectal ultrasound can be a substitute for a transvaginal one. In one study in Korea, they discovered that this transrectal ultrasound was as effective in detecting PCOS signs as the transvaginal.

It’s worth noting that medical guidelines say that aspirin and NSAIDs (nonsteroidal anti-inflammatory drugs) shouldn’t be taken at least three days after a transrectal ultrasound to avoid rectal bleeding.

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When to do PCOS ultrasound?

The transvaginal ultrasound for PCOS is usually performed on days 2-7 of the menstrual cycle. This is because growing follicles may hide smaller ones or change ovarian volume if performed later in the cycle. In the case of an irregular menstrual cycle, the procedure may be done any day or after progesterone-induced bleeding (withdrawal bleeding). But this is what shall be discussed with a health care provider.

Why do you need an ultrasound for PCOS?

There is a special criteria for diagnosing PCOS – the Rotterdam Criteria, created in 2003. This means that the presence of two or three of the following criteria is required for diagnosing PCOS.

1. Oligo-amenorrhea: absent or irregular menstrual cycles.
2. Hyperandrogenism: high androgens or male hormone levels.
3. Polycystic ovaries: the presence of excess follicles and/or their disturbed morphologia. These follicles are also known as cysts. Also, an elevated serum of anti-Mullerian hormone AMH in the hormone test can be a hallmark for PCOS.

This last sonographic criteria with polycystic ovaries (excessive follicles) is exactly what an internal transvaginal (pelvic) ultrasound can detect. This criteria is based on the study where females with PCOS had significantly more follicles in the 2‐5 mm range than women with tubal or male factor infertility. 

However, a PCOS ultrasound might not be needed for the diagnosis of PCOS if two other criteria are confirmed or if one of them is confirmed together with an elevated serum AMH.

What does PCOS look like on ultrasound?

Normal ovary ultrasound vs PCOS ultrasound results will be different on the sonogram picture.

One of the PCOS common signs is an excess number of immature follicles in the ovaries. These characteristics are what are usually observed on a transvaginal ultrasound.

At the same time, PCOS on ultrasound will look like an increase in the size of the ovaries, small cysts (look like black circles on the sonogram). More specifically, the PCOS cysts will likely have the following characteristics, according to the 2003 Rotterdam consensus:

• 12 or more follicles in each ovary; 
• Follicles measuring 2-9 mm in diameter;
• Increased ovarian volume (over 10 ml) in a single ovary or both.

In a polycystic ovary, the length and width, as well as the ovarian area, are increased. 

To summarize, this is what PCOS looks like on ultrasound:

• enlarged ovary size;
• multiple small follicles of similar size;
• increased ovarian volume;
• peripheral distribution of the follicles;
• higher stromal blood flow (stroma is a type of connective tissue).

On the contrary, in a female without PCOS, the ultrasound picture will be different: the normal healthy ovary is smaller in size (usually less than 10 ml), with few randomly distributed follicles of varying size.

However, this can be tricky. Sometimes, the ovaries may appear normal in PCOS on ultrasound, and polycystic ovarian morphology (PCOM), a disbalance, may be detected in females without the syndrome. However, females with PCOS usually have larger ovaries, and the number of follicles tends to be higher.

Is PCOS ultrasound accurate?

The trick with such PCOS ultrasound is that some women have normal ovarian volume but abnormal ovarian morphology (size, volume). In one study, for instance, they concluded that ovarian morphology is more reliable than ovarian volume in diagnosing PCOS.

Transvaginal and transrectal ultrasound methods are considered ones of the most reliable to spot the PCOS markers (cysts). It’s worth remembering, though, that an ultrasound alone is not enough to confirm PCOS. Usually, complex assessments are needed.

Can normal ultrasound detect PCOS? TVS contradictions

Normal PCOS ultrasound, meaning external transabdominal ultrasound, can sometimes substitute a transvaginal one. Although transvaginal ultrasound is considered a common and safe procedure, there can be certain contradictions. Some of them are:

1. Imperforated hymen;
2. Vaginal obstruction;
3. Recent vaginal surgery;
4. Rupture of membranes and bleeding from placenta previa in a pregnant female;
5. When a patient simply doesn’t give consent for this procedure.

Also, medical guidelines do not recommend performing transvaginal ultrasound for females within 8 years after their first period. This is actually challenging since PCOS is a condition that is actually most common among younger females during their reproductive years. For instance, PCOS is found to be more prevalent among women aged 21-34 years than those in their 35-44 years. 

Moreover, some studies say that the age of PCOS onset can be even younger – starting from 13 or even earlier – 9-12 years old. What is interesting is that girls born with IVF might even have higher risks of developing PCOS at their younger age since these kids have higher dehydroepiandrosterone sulfate (DHEAS) and luteinizing hormone (LH) levels in puberty.

In these cases, a normal transabdominal (external) ultrasound can be a solution. Normal ultrasound can also spot signs of PCOS, such as larger ovarian volume. This can also detect cysts, although the result might not be as precise as in an TVS. In a study in 2013, they found that follicle number and ovarian volume on transabdominal ultrasounds were not precise and did not have a high diagnostic power.

In one study, for example, they compared how effective both types of ultrasounds were in detecting pelvic masses. As a result, six simple cysts and four complex pelvic masses were only seen in transvaginal sonograms. Moreover, TVS results were more helpful in females with obesity and in those patients who can’t achieve a proper bladder filling, which is required for the ordinary ultrasound.

This suggests that transvaginal or a transrectal ultrasound are superior options for PCOS detection when compared to a conventional abdominal one. 

Final verdict

Ultrasound is a commonly used tool to spot potential signs of PCOS.

There are three types of ultrasounds: transabdominal (non-invasive), transvaginal, and transrectal ultrasounds (invasive). The last two invasive types are used for PCOS signs detection (excessive number of follicles and their morphology like size and volume).

The transvaginal and transrectal ultrasounds are found to be equally effective, as well as more effective in PCOS diagnostics when compared to a normal transabdominal ultrasound.

There can be certain contradictions for the two invasive types of ultrasounds (transvaginal and transrectal). This is when a transabdominal ultrasound, usually in combination with other diagnostic tests like hormone level tests, can be used to detect signs of PCOS.

Normal ovary ultrasound vs PCOS ultrasound look different from the sonogram picture. The results are calculated by the software tools and analyzed by a health care provider.

For PCOS to be diagnosed, this internal ultrasound alone is not enough, and a combination of symptoms shall be found. Also, this ultrasound for PCOS is not a must, and a test for elevated serum of anti-Mullerian hormone (AMH) can be an alternative that can also indicate follicle excess (a sign of PCOS).