Doctors usually offer ultrasound examinations to people who present with symptoms of endometriosis to look for signs of tissue growth in and around the pelvis.

Endometriosis is an inflammatory condition that occurs when tissue from the uterine lining develops outside of the uterus. Symptoms include pelvic pain, painful periods, and painful intercourse. Current estimates suggest that it could affect more than 11% of women between the ages of 15 and 44 years in the United States.

This article looks at ultrasound reliability, what happens during a scan, and whether there are more accurate ways of diagnosing endometriosis.

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A doctor may offer an ultrasound to a person who presents with symptoms of endometriosis.

An ultrasound uses high-frequency sound waves that bounce off organs and tissues in the pelvis to create a picture of the inside of the body.

A doctor may use a transducer pressed against the abdomen (transabdominal ultrasound) or inserted into the vagina (transvaginal ultrasound). Both work in the same way to capture an image.

A 2016 Cochrane review looked into the accuracy of ultrasound scans in diagnosing endometriosis. The review concluded that doctors may be able to identify certain severe cases of endometriosis via ultrasound, which could eliminate the need for further exploratory tests. However, endometriosis may still be present even if an ultrasound scan does not detect any. In this case, a person may require further tests.

In 2016, a consensus group called International Deep Endometriosis Analysis published a systematic approach to evaluating endometriosis with ultrasound. They advocated using a four-step method to improve the diagnosis of endometriosis by ultrasound, including:

  1. examining the uterus, ovaries, and fallopian tubes for growths by transvaginal scan
  2. looking for “soft markers,” such as ovarian mobility and site-specific tenderness
  3. applying gentle pressure to specific areas within the pelvis to check movement and mobility
  4. looking for tissue at the front and back of the pelvis, including the bladder

Authors argue that this rigorous approach would help standardize a diagnostic system and ultimately improve treatment for people with endometriosis.

During an ultrasound scan, an individual lies on their back. The doctor may request that they have an empty or full bladder, depending on the part of the pelvis they intend to check or the method of the ultrasound scan.

Transabdominal ultrasound

This noninvasive method involves pressing on the abdomen using a device called a transducer. The doctor or sonographer applies a cool jelly to the stomach before sliding the transducer over the skin. It may feel cold, and people may feel some pressure, but it should not hurt.

Transvaginal ultrasound

During menstruation, people must remove tampons before a transvaginal scan.

The doctor or sonographer inserts a small, finger-width ultrasound probe (transducer) into the vagina. They move the transducer slightly to capture images of the pelvis and look for evidence of endometriosis.

Transvaginal scans should not hurt, but they may feel slightly uncomfortable.

During an ultrasound, a doctor looks for signs that indicate the severity of endometriosis. The American Society of Reproductive Medicine has set out four endometriosis stages:

  • Stage 1: Minimal: There are a few isolated and superficial implants of endometrial tissue.
  • Stage 2: Mild: There are several implants of endometrial tissue that are slightly more deeply embedded.
  • Stage 3: Moderate: There are many deep implants, one or both ovaries have small cysts on them, and there are fibrous bands between tissues and organs called filmy adhesions.
  • Stage 4: Severe: There will be many deep implants, one or both ovaries will have large cysts, and many dense adhesions are present.

Yes, someone with endometriosis can have a normal ultrasound. Ultrasound is a valuable tool in diagnosing endometriosis, but it is not entirely accurate.

A 2021 Cochrane review into ultrasound as a diagnostic tool found that endometriosis may still be present even if a doctor finds no evidence during an ultrasound scan.

Apart from ultrasound, there are other ways to detect endometriosis, with varying levels of accuracy and reliability.

MRI scan

An MRI scan creates an image of the inside of the body. A doctor may use this in place of ultrasound to look for endometrial tissue.

Biomarkers

Specific biomarkers, such as elevated protein levels, may signify endometriosis. However, tests to measure these biomarkers are not reliable enough on their own to show someone has the condition.

Keyhole surgery and biopsy

Laparoscopy or keyhole surgery is a definitive way to diagnose endometriosis. A surgeon makes a small cut near the navel during the procedure and inserts a camera called a laparoscope into the pelvis. This allows them to look at endometrial tissues, including cysts or adhesions, and take a sample for further testing.

Endometriosis occurs when tissue that usually lines the uterus every month in preparation for a fertilized egg grows outside the uterus instead. Tissue may develop on the outer surface of the uterus, behind the uterus, or elsewhere in the reproductive system, such as in or on the:

Less commonly, tissue may develop in other parts of the pelvic area, such as the vagina, cervix, vulva, or bowels. Rarely, endometrial tissue may grow in other body parts, such as the brain, lungs, eyes, or skin.

Endometriosis is a common health problem for women. The Office on Women’s Health says around 11% of women aged 15–44 years in the U.S. have this condition. Symptoms include:

Learn more about endometriosis here.

Endometriosis is a common and painful condition that happens when tissue from the uterine lining grows outside of the uterus. More than 1 in 10 women experience the condition.

Ultrasound scans are valuable in diagnosing endometriosis and evaluating the severity of the condition. However, their accuracy may depend on the person performing the scan. Keyhole surgery remains the gold standard for diagnosing endometriosis.