4 Stages of Endometriosis and What They Can Mean

Doctors may use stages to classify your endometriosis, but these stages don't always correspond to your quality of life.

If you've been diagnosed with endometriosis, you might have been told your condition is at a specific stage. Healthcare providers use several staging systems to classify endometriosis. Defining your stage is one of the factors you and your healthcare provider will consider when planning your treatment.

Endometriosis is a condition in which tissue similar to endometrial tissue (which lines the uterus) implants outside the uterus in places like the fallopian tubes, ovaries, and other organs in the pelvic region, according to Johns Hopkins Medicine.

This can cause cyclical shedding, inflammation, cysts, and scar tissue throughout the pelvic region. People with endometriosis may experience chronic pelvic pain, pain during sex, painful urination, gastrointestinal issues, abnormal or heavy periods, and infertility.

The American Society of Reproductive Medicine's (ASRM) four stages system is one of the most widely used methods of staging the severity of endometriosis. Staging is based on factors like the location, size, and depth of endometrial tissue spread.

Staging can only be done during and following surgery. It's important to note that if your surgeon gives you a stage, this can help you understand what they are referring to, but staging is not a necessary part of disease management. For example, the stage you're given may not, in your experience, accurately define your quality of life.

Here are the basics of the ASRM staging system and other staging systems used to describe endometriosis.

The ASRM Stages of Endometriosis

The ASRM patient site has a booklet on endometriosis that delves into the condition and staging process. Here is an overview of the key terms involved in staging and what each of the four stages means. However, understanding this staging system also means considering its limitations (explained later in this article).

Key Terms Involved in the I-IV Staging System

Per the ASRM, the I-IV staging system is a point system based on the location, extent, and depth of endometriosis implants; the presence and severity of endometrial adhesions; and the presence and size of ovarian endometriomas. Points are given for each of these categories, with higher points meaning a higher stage.

ASRM defines these terms as:

Endometriosis Implants: Endometrial cells that grow and spread outside of the uterus. They are typically small and flat.

Endometrial Adhesions: Tissue that forms in bands and is fibrous. These tissues can bind organs (typically abdominal and pelvic organs in endometriosis) together.

Note: A study published in the International Journal of Fertility and Sterility in 2019 explained that adhesions form as part of the inflammatory process in endometriosis. When endometrial implants (tissue outside of the uterus) bleed, it causes an inflammatory reaction that results in the development of adhesions, or bands between organs.

There are different thicknesses and severities of these bands, with stages 3 and 4 of endometriosis having dense adhesions, per the ASRM.

Ovarian Endometriomas: These are also known as chocolate cysts because they are filled with blood that turns brown over time. The cysts are found on the ovaries and occur when tissue spreads and grows there.

Additionally, an article published in the Cureus in 2018 described the point ranges for each stage:

4 Stages of Endometriosis

Stage 1 is "Minimal Endometriosis"

Per ASRM, in Stage 1, there may be superficial implants and mild adhesions.

The point score for minimal endometriosis is between 1-5, per the 2018 study in Cureus.

Stage 2 is "Mild Endometriosis"

Per ASRM, in stage 2, the implants may be superficial or deep, and adhesions are mild. In stage 2, endometriosis may be more widespread, and deeper implants may be present.

The point score for mild endometriosis, per the 2018 study in Cureus, is 6-15.

Stage 3 is "Moderate Endometriosis"

Per ASRM, in stage 3, "deep" endometriosis (defined as infiltrating greater than three centimeters) is present, and adhesions may be dense instead of filmy and thinner. Endometriosis is more widespread than in Stage 2. And, while some implants may be superficial, there is more widespread deep endometriosis. Additionally, while some adhesions may still appear filmy, there are denser adhesions in moderate endometriosis.

The point score for mild endometriosis, per the 2018 study in Cureus, is between 16-40.

Stage 4 is Severe Endometriosis

Per ASRM, in stage 4, deep endometriosis is present along with dense adhesions. Again, there may be superficial endometriosis and filmy adhesions. However, the disease is more widespread than in Stage 3. While some endometriosis implants may be superficial and some adhesions filmy, they are coupled with deep endometriosis and dense adhesions.

This is the most severe form of endometriosis, with the point score for mild endometriosis, per the 2018 study in Cureus, >40.

Limitations of the ASRM Staging System

The escalating severity of the four ASRM stages might give the impression that endometriosis first starts in one part of the body before spreading to more distant organs.

But endometriosis can be widespread from the beginning, Hugh Taylor, MD, vice president of the American Society for Reproductive Medicine and chair of obstetrics, gynecology, and reproductive science at Yale School of Medicine, told Health.

"If you want to say someone is better or worse after some kind of treatment or surgery, or if you want to compare one surgery to another, you really need a system and formula in place to act like some kind of quantitative comparison," Dr. Taylor said about the stages. "But this is not the same type of staging system that would have meaningful prognostic value, like in cancer."

And the standard four endometriosis stages don't correlate to how much things like infertility or chronic pain affect individuals with the condition. This also means that while defining the stage can help guide treatment, staging isn't the only factor considered when it comes to treatment.

"Patients like to know how widespread it was," Dr. Taylor said. "But someone with minimal to mild endometriosis can have more pain than someone with severe endometriosis." Additionally, Dr. Taylor said that an individual with Stage 1 endometriosis could have more fertility challenges than someone with Stage 4 endometriosis.

How Endometriosis Is Diagnosed and Staged

Per the Office on Women's Health, laparoscopy is the only way to confirm an endometriosis diagnosis. During this procedure, a small instrument and camera are inserted into the pelvic region. This allows the healthcare provider to see the endometrial growths and take a tissue biopsy if necessary.

According to the ASRM, laparoscopy is the only way healthcare providers can evaluate the extent of endometriosis to stage it according to the I-IV system. Additionally, if fertility is a concern, during a laparoscopy, a healthcare provider may look to see if your fallopian tubes are open. The healthcare provider does this by injecting a special dye and seeing if it goes through the fallopian tubes.

The healthcare provider can also treat endometriosis during a laparoscopy by removing the endometriosis, scar tissue, and ovarian cysts they can see.

Laparoscopy can also help to reduce pain and preserve fertility if the endometriosis is removed during the laparoscopy. However, per the ASRM, many individuals experience a return of their symptoms within a few years.

Other diagnostic procedures can possibly indicate endometriosis but often miss the disease. These procedures include:

  • A pelvic exam to see if the healthcare provider can feel large cysts or scar tissue behind the uterus
  • Imaging, such as an ultrasound or magnetic resonance imaging (MRI), to look for ovarian cysts and take pictures of the inside of your body

Furthermore, prescribed medications, such as hormonal birth control, may decrease pelvic pain during periods. A medication called gonadotropin-releasing hormone agonists might also be prescribed. This medication works by blocking estrogen, preventing your menstrual cycle, and possibly decreasing pelvic pain. If these medications relieve your symptoms, it can indicate endometriosis.

Other Methods of Staging

Other ways to classify endometriosis have been proposed that better recognize patient symptoms. For example, in a study published in Human Reproduction in 2017, the authors emphasized the need for a global consensus on how to classify endometriosis that also incorporates the views of those with the condition—such as the pain individuals with endometriosis may experience.

Enzian Scale

A study published in Global Reproductive Health in 2020 also described the dilemma of scoring endometriosis to represent better the symptoms associated with the condition.

The authors recommended utilizing the Enzian Scale when deep infiltrating endometriosis (DIE) is present. This scale divides the location of endometrial tissue into eight compartments based on location and includes a severity grade based on size.

The authors suggest better categorizing the extent of DIE lesions and where they are located through the Enzian Scale, which may better correlate with where pain is felt and how severe the symptoms are.

The eight compartments, as stated in the article, are:

  • Compartment A (vagina, rectovaginal septum)
  • Compartment B (uterosacral ligaments, parametrium)
  • Compartment C (rectum, sigmoid colon)
  • Compartment FA (adenomyosis)
  • Compartment FB (urinary bladder)
  • Compartment FU (intrinsic involvement of the ureters)
  • Compartment FI (intestine)
  • Compartment FO (other localizations)

The size of endometrial tissue is described as severity grades 1-3. Grade 1 is less than one centimeter; grade 2 is one to three centimeters; and grade 3 is greater than three centimeters.

For example, an A1 classification means the individual has DIE in compartment A, which consists of the vagina and rectovaginal septum, and is less than one centimeter.

The authors indicate that using the four stages scoring system and the Enzian scoring system when DIE lesions are present gives a better picture of endometriosis than using either system on its own.

Descriptive Classifications of Endometriosis

Tamer Seckin, MD, an endometriosis specialist at Seckin MD Endometriosis Center, has divided up endometriosis into categories depending on where the disease is located and how it affects the person:

Category 1: Peritoneal Endometriosis

Endometriosis is located on the peritoneum, a membrane that lines the abdomen. This is the most minimal category.

Category 2: Ovarian Endometriomas

Endometriomas, or cysts, in the ovaries risk bursting and spreading the endometriosis to other nearby organs.

Category 3: Cul-de-sac obliteration

Endometriosis has infiltrated organs in the pelvic region, like the rectum and the outside of the uterus.

Category 4: Deep Infiltrating Endometriosis

Infiltrating endometriosis is when the condition becomes invasive and penetrates other organs, such as the bladder or bowel wall.

Category 5: Frozen Pelvis

This is when endometriosis deeply infiltrates areas in the pelvis, including ligaments, nerves, and muscle tissue. The surrounding pelvic organs may become "cemented" or frozen.

Delays in Endometriosis Diagnosis

To cut down on time it takes to diagnose and treat endometriosis, there is a movement among healthcare providers to start recognizing the signs of the disease clinically, without the need for surgery, Dr. Taylor said.

Yale Medicine explained that when endometriosis symptoms are mistaken for other, more common period symptoms, or when females have no symptoms, it can lead to delays in diagnosis. Per Yale Medicine, it takes, on average, 10 years for a female to receive a proper endometriosis diagnosis.

One classic sign of endometriosis is painful periods, with pain that lasts beyond the menstrual cycle. Sometimes, a physical exam can reveal cysts, or an ultrasound can show signs of scar tissue, such as the pulling of organs, like the uterus, toward a certain side.

"The first thing I always hear from endometriosis patients is that they complain about the pain, and their mother, friends, and even their physicians, say, 'Oh, periods are supposed to hurt, that's normal,'" Dr. Taylor said. "It's not until they really start to get disrupted, like missing school or work, that people start taking it seriously," said Dr. Taylor.

Raising Awareness

Dr. Taylor advised that taking a person's pain seriously could save them years of frustrating misdiagnoses. Earlier treatment could also curb symptoms sooner, reducing the development of painful and debilitating scar tissue.

If an individual is diagnosed with endometriosis, treatment will depend on their symptoms and reproductive goals. Medications that affect hormones might control the pain in some mild cases. Fertility treatments may be the best option if the primary concern is infertility.

Drugs that affect hormone levels can be effective, although some come with severe side effects. The American College of Obstetricians and Gynecologists (ACOG) notes several medications that are typically used, ranging from over-the-counter medications such as NSAIDs to help with pain to hormonal medications that block the effects of certain hormones.

While medications likely won't eliminate endometrial tissue already present, they may slow the growth of new tissue and prevent new adhesions.

"Surgery can be a treatment, I think it's a treatment—but of last resort," Dr. Taylor said. "It's about getting people treated earlier before [endometriosis] really disrupts their lives."

A Quick Review

There are variations in staging endometriosis. The ASRM's four stages scale is still the most commonly used classification system. Still, it is important to remember that whether you are diagnosed with stage 1 or stage 4, endometriosis may have a significant impact on your day-to-day life.

Even at stage 1, the condition may cause significant pain or problems with fertility. You may also have DIE lesions that could affect your quality of life, even in the lower ASRM stages.

If you have concerns about endometriosis, advocating for yourself and reaching out to a healthcare provider is an important step you can take for your health.

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