How Endometriosis Is Diagnosed

Challenges remain in identifying this condition

In This Article

Endometriosis is an often painful disorder in which the lining of the uterus, called the endometrium, extends beyond the confines of the uterus. Endometriosis most commonly affects the ovaries, fallopian tubes, and tissues of the pelvic wall. Since the endometrial overgrowth will break down and bleed in the same way that it would during a normal menstrual cycle, any displaced tissue can become trapped, causing irritation and the formation of adhesions (scar tissues that stick organs and tissues together).

A correct diagnosis is essential to delivering timely and effective treatment of endometriosis. This typically involves a review of your symptoms, a physical exam, and a combination of lab and imaging tests to identify the lesions and adhesions characteristic of the disease. Your condition would then be staged (categorized by severity) to direct the appropriate course of treatment.

How endometriosis is diagnosed
Verywell / Cindy Chung

Although the symptoms of endometriosis (pain and bleeding, among others) can be striking and severe, diagnosing the disease can often be challenging. This is due in part to the fact that pain and bleeding can be caused by any number of other conditions, some of which can co-occur with endometriosis. 

It is also not unusual for a woman with endometriosis to have other pain syndromes, such as painful bladder syndrome, irritable bowel syndrome, or fibromyalgia—all of which can mimic the symptoms of endometriosis. Even if the characteristic lesions are found, endometriosis may be only one of several possible causes.

Moreover, the extensiveness of lesions doesn’t necessarily confer the severity of symptoms. Some women may have severe symptoms and a complete absence of lesions, while others will have widespread lesions and no symptoms. The wide variability of the symptoms can lead to frequent misdiagnosis, delayed treatment, and a reduced quality of life.

According to a 2019 review of studies in the American Journal of Obstetrics and Gynecology, this average time between the onset of symptoms and diagnosis of endometriosis is no less than four to seven years.

These barriers have led some experts to call for a change in how endometriosis is defined. Rather than basing a diagnosis on the histology (microscopic characteristics) of the disease, they believe that greater emphasis should be placed on symptoms and less on the presence or absence of lesions.

Self-Checks/At-Home Testing

There are no in-home tests or self-exams able to diagnose endometriosis. With that being said, knowing the signs and symptoms of the endometriosis—and how to communicate them to your doctor—can increase your chance of a correct diagnosis.

One of the challenges in diagnosing endometriosis is the "normalization" of symptoms, not only by doctors but by women themselves.

Since the symptoms typically occur in tandem with menstruation, people will often discount them, assuming it's a heavy period and fail to investigate the symptoms until months or years later.

The very fact that the symptoms occur during your period should be a warning sign that endometriosis is a possibility. Although pain and bleeding can occur outside of your normal cycle, it is the cyclic nature of endometriosis that most commonly typifies the disorder.

Other tell-tale signs to look for include:

  • Chronic non-menstrual pelvic pain. The pain may occur on its own or in response to typically non-painful stimuli (such as intercourse or the insertion of a tampon).
  • Bleeding between periods, which should never be considered normal. Painful urination (dysuria) and clotting may also accompany this symptom.
  • Having other pain syndromes, such as IBS and migraines, which should also raise the possibility of endometriosis. According to research published in Clinical Obstetrics and Gynecology, 20 percent of women with endometriosis will have co-occurring pain syndromes.
  • Painful defecation (dyschezia), which can occur if the endometrial lesions have infiltrated the bowel.
  • Failure to achieve pain relief from nonsteroidal anti-inflammatory drugs (NSAIDs) like Motrin (ibuprofen) or Aleve (naproxen), which is also characteristic. While NSAIDs can reduce the pain and discomfort of your period, they are usually inadequate when treating endometriosis.

Even if your symptoms aren’t overt or consistent, it’s important to convey them to your doctor. If your doctor minimizes them or fails to listen to you, do not hesitate to seek a second option from a qualified gynecologist.

The Bottom Line

If you minimize your endometriosis symptoms, your doctor will likely do the same. Be sure to raise any concerns you have, no matter how minimal. This way, any pain or signs of complication will not go overlooked, whether it's endometriosis or another underlying condition.

Labs and Tests

The investigation by your doctor will standardly begin with a review of your symptoms, medical history, and risk factors for endometriosis. This would be followed with a pelvic examination in which you would be asked to disrobe from the waist down. Our Doctor Discussion Guide below can help you start a conversation with your doctor about interpreting lab results and more.

Endometriosis Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

Doctor Discussion Guide Woman

Pelvic Exam

The investigation would be centered around the pelvis but may also include the lower abdomen. This would typically involve a bimanual pelvic exam, in which external tissue is palpated (touched) with one hand while the vagina is examined internally with the other. A bimanual exam can sometimes identify nodules, the thickening of ligaments, or excessive tenderness (hyperalgesia) suggestive of endometriosis.

Other common signs include a "frozen pelvis" (due to excessive build-up of scar around pelvic ligaments) and a "fixed uterus" (in which the uterus does not move around freely with palpation).

The doctor may also use a speculum to view the vagina internally. In some cases, a speculum exam can reveal the overgrowth of the tissue or a "displaced cervix" (in which the position of the cervix is altered due to scarring). 

Generally speaking, though, a speculum is rarely useful in making a diagnosis since the visual clues tend to develop only in the later stages of the disease. 

A pelvic exam is only moderately reliable in making a diagnosis.

According to a 2010 review in Clinical Obstetrics and Gynecology, 47 percent of women with endometriosis will have a perfectly normal pelvic exam. A pelvic exam tends to be more reliable when you are symptomatic and/or having your period.

Lab Testing

A lab test, known as cancer antigen 125 (CA125) blood test, may be used to support a diagnosis. The CA-125 test is typically used when ovarian cancer is suspected but can also point to other conditions affecting the female reproductive tract including endometriosis, fibroids, benign tumors, and cancers of the endometrium or fallopian tubes.

The CA125 is prone to false positives and false negatives and tends to be most accurate during advanced disease. The normal value for the CA125 test is anything less than 46 units per milliliter (U/mL). However, it is important to remember that a normal CA125 value does not rule out endometriosis or any other condition affecting the female reproductive organs.

For this reason, the CA125 is not used to make a definitive diagnosis. It is typically performed if your symptoms and pelvic examination suggest endometriosis. The results of these exams can help your doctor decide if more invasive investigations are warranted.

Despite its use in diagnosis, the CA125 is not used to screen for endometriosis or any other disease.

Imaging

Your doctor may order imaging tests if endometriosis is strongly suspected but the lesions are too deep to be identified by a pelvic exam. Generally speaking, imaging tests are only of limited use as smaller lesions and adhesions tend to be missed.

There are three imaging tests commonly used for the diagnosis of endometriosis: ultrasound, magnetic resonance imaging (MRI), and computed tomography (CT).

Ultrasound

Ultrasound is a technology in which sound waves create detailed images. To capture images of your reproductive organs, a device called a transducer is pressed against your abdomen or inserted into your vagina (transvaginal ultrasound). Doing so can reveal the abnormal thickening of tissues, endometriomas (cyst-like masses within an ovary), and deep lesions and nodules.

Magnetic Resonance Imaging (MRI)

MRI is a technology that uses magnetic and radio waves to create highly detailed images, mainly of soft tissue. The MRI is more accurate than ultrasound but also far more expensive. It would more likely be ordered if endometriosis is strongly suspected but no other non-surgical evaluations have been able to support the diagnosis.

Computed tomography (CT)

This is a form of X-ray in which a computer renders cross-sectional "slices" of your organ to create three-dimension images. It is not helpful for diagnosing endometriosis but may be ordered if the kidneys or urethra (the tube through which urine leaves the body) is involved.

In addition to imaging tests, there are other surgical procedures that your doctor may use to reach a diagnosis of endometriosis.

Laparoscopy

Laparoscopy is a surgical procedure in which a fiber-optic scope is inserted through the wall of your abdomen to view the internal organs. It is considered the gold standard for the diagnosis of endometriosis, allowing the direct visualization of tissue overgrowth.

The test is performed under general anesthesia in a hospital. Generally, a small incision is made near your navel through which carbon dioxide is injected to inflate the abdomen. A slender, lighted laparoscope is then inserted to view your reproductive organs on a video monitor.

Once the examination is completed, the laparoscope is removed and the incision stitched. A laparoscopy can oftentimes be performed on an outpatient basis. While valuable, however, the test is not without its limitations.

Depending on how overt the overgrowth is, the surgeon may not be able to confirm endometriosis on visualization alone.

In many cases, a biopsy would be performed in which tissue is snipped off during the procedure and sent to the lab for microscopic evaluation.

According to a study from the University of Kiel in Germany, 15.9 percent of women with no signs of endometriosis in a laparoscopic exam were confirmed to have endometriosis based on the evaluation of a tissue biopsy.

Disease Staging

Once endometriosis has been definitively diagnosed, the disease will be staged to direct the appropriate course of treatment. Laparoscopy is required to stage the disease—endometriosis cannot be staged with a pelvic exam or imaging tests alone. 

The American Society for Reproductive Medicine (ASRM) classification of endometriosis is currently the most widely used staging system. It operates on a scale of 1 through 4, with points given for the number, size, location, and severity of lesions, adhesions, and cysts.

The ASRM classification breaks down as follows:

  • Stage 1 (1 to 5 points) indicates minimal visual evidence of endometriosis with a few superficial lesions.
  • Stage 2 (6 to 15 points) indicates mild disease with more lesions that are deeper.
  • State 3 (16 to 40 points) is moderate endometriosis with many deep lesions, small cysts on one or both ovaries, and the presence of adhesions.
  • Stage 4 (over 40) is a severe form of the disease with many deep lesions, large cysts on one or both ovaries, and multiple adhesions.

It is important to note that the staging score in no way correlates to the presence or severity of symptoms. It is simply used to ensure that the condition is neither undertreated nor overtreated.

Laparoscopy can also be used to surgically treat endometriosis or monitor your response to treatment after surgery.

Differential Diagnoses

At first glance, the symptoms of endometriosis can readily be attributed to any number of other conditions. At the same time, it is not uncommon for endometriosis to co-occur with other gynecological, urological, or digestive disorders, each of which may require different treatments.

To ensure the correct diagnosis, your doctor may order other tests (such as a PAP smear and pregnancy test) to rule out other possible causes of your symptoms. This is especially true if the results of the preliminary tests are anything less than conclusive.

Your doctor may want to investigate the following conditions (among others).

  • Pelvic inflammatory disease (PID) is an infection of the female reproductive organs. It usually involves a sexually transmitted bacteria (like chlamydia or gonorrhea) that has moved from the vagina to the uterus, fallopian tubes, or ovaries. PID can often be confirmed with a bacterial culture of the vaginal discharge.
  • Ovarian cysts are solid or fluid-filled sac within or on the surface of an ovary. The non-cancerous cysts can be caused for many reasons, including polycystic ovary syndrome (PCOS), and may be differentiated by transvaginal ultrasound or laparoscopic biopsy.
  • Irritable bowel syndrome (IBS) is characterized by bouts of diarrhea, constipation, and abdominal cramping. The diagnosis of IBS is typically based on the absence of ultrasound, MRI, or laparoscopic evidence.
  • Interstitial cystitis (IC) is a chronic bladder condition causing pain and pressure in the bladder area. It can usually be differentiated with cystoscopy in which a flexible scope is inserted into the urethra to view the interior of the bladder.
  • Adenomyosis is a condition in which the endometrium invades and penetrates the wall of the uterus. It is usually differentiated with an MRI and can often co-occur with endometriosis.
  • Uterine fibroids are non-cancerous growths in the uterus that often appear during the childbearing years. They are not associated with an increased risk of uterine cancer. Their fibrous nature of growths is such that they can usually be differentiated with a transvaginal ultrasound.
  • Ovarian cancer generally only becomes symptomatic when the malignancy is as advanced. Symptoms may include a lack of appetite, increased abdominal girth, constipation, the frequent need to urinate, and chronic fatigue. A transvaginal ultrasound combined with a strongly positive CA125 blood test can usually help differentiate ovarian cancer from endometriosis.

A Word From Verywell

Be sure to speak with your doctor or healthcare provider if you are experiencing any unexplained symptoms of pain or discomfort. While endometriosis can be difficult to diagnosis, the best first step is discussing your symptoms with a professional who can help narrow down the underlying condition. Even if you don't have endometriosis, you may have another treatable condition. As with any health matter, early intervention and treatment is the best route for coping and recovery.

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Article Sources

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