Stages of Endometriosis—What They Mean and Don't Mean

Experts use stages to classify endometriosis by severity, but the stage doesn't always correspond to the pain and discomfort levels.

According to Johns Hopkins Medicine, endometriosis is a condition in which endometrial tissue that lines the uterus begins to spread outside the uterus and implant in places like the fallopian tubes, ovaries, and other organs in the pelvic region.

Johns Hopkins explains that when it grows normally inside the uterus, endometrial tissue sheds during every menstrual cycle, creating a monthly period. But in endometriosis, endometrial tissue also sheds when it is implanted or attached to organs outside of the uterus. This shedding can cause inflammation, cysts, and scar tissue throughout the pelvic region.

Individuals with endometriosis may experience chronic pelvic pain, pain during sex, painful urination, gastrointestinal issues, abnormal or heavy periods, and infertility.

The degree of spread of the endometrial tissue and how deeply it has infiltrated are important considerations in staging.

What Happens After an Endometriosis Diagnosis?

The Office on Women's Health explained how endometriosis is diagnosed. First, the healthcare provider may do a pelvic exam to see if they can feel large cysts or scar tissue behind the uterus. Then, they may use various imaging, such as an ultrasound or magnetic resonance imaging (MRI). If endometriosis is highly suspected, there are hormonal medications that may help. If these improve the symptoms, it may help confirm a suspected diagnosis of endometriosis.

However, the gold standard for confirming an endometriosis diagnosis is through a surgical procedure called laparoscopy. This allows the healthcare provider to see the endometrial growths if visually present and take a tissue biopsy if necessary. Per the Office on Women's Health, surgery is the only way to confirm an endometriosis diagnosis.

Endometriosis Staging

Once the condition is diagnosed, the healthcare provider determines which stage it is. Being able to see endometriosis implants and scarring is what enables healthcare providers to classify the disease into stages. Johns Hopkins Medicine explains there are four stages of endometriosis. They are Stage 1 (minimal), Stage 2 (mild), Stage 3 (moderate), and Stage 4 (severe).

A study published in 2020 in the journal Global Reproductive Health described the American Society for Reproductive Medicine (rASRM) scores that range from stage 1-4 and explained it is the most widely utilized scoring method for endometriosis. However, the study notes one of the problems with this scoring system is that while it considers the extent of the endometrial adhesions, it does not factor in deep infiltrating endometriosis (DIE).

Instead, the authors recommend utilizing a scale called the Enzian when DIE lesions are present. This scale divides the location of lesions into eight compartments based on where the lesions are and a severity grade based on the size of the lesion. 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 lesions are described as severity grades 1-3. Grade 1 are lesions less than 1cm; grade 2 are lesions 1-3cm, and grade 3 are lesions >3cm.

For example, an A1 classification means the individual has DIE lesions in compartment A, which consists of the vagina and rectovaginal septum. The 1 means, the lesion is less than one centimeter. Another study, published in 2021 in the Scandanavian journal Acta Obstetricia et Gynecologica Scandinavica, explained how an individual may only have Stage 1 or 2 endometriosis, but could also have DIE lesions that cause a variety of symptoms depending on their locations.

What the rASRM Four Stages Don't Mean

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

But endometriosis doesn't grow like cancer, as the disease 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 a cancer."

For instance, the standard four endometriosis stages don't correlate to how badly things like infertility or chronic pain affect individuals with the condition. Unfortunately, this also means that the stages don't necessarily guide treating endometriosis in different patients.

"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." Dr. Taylor added that an individual with Stage 1 endometriosis might be more infertile than someone with Stage 4 endometriosis.

Alternative Methods of Staging

Because of the difficulty in describing endometriosis in a meaningful way for treatment, others have tried to propose different ways to classify the disease. For example, a study published in Human Reproduction in 2017 focused on the dilemma of classifying endometriosis. The authors emphasized the need for a global consensus on how to classify it that also incorporates the views of those with the condition—such as the pain individuals with endometriosis may experience.

For example, one healthcare provider, Tamer Seckin, MD, an endometriosis specialist at Seckin MD Endometriosis Center, has divided up the disease into categories depending on where the disease is located and how it affects the patient:

Category 1: Peritoneal Endometriosis

The 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 the 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, which then progress to pain that lasts beyond the menstrual cycle. Sometimes, physical exams can reveal cysts, and other times ultrasounds can show that organs like the uterus might be pulled or tilted toward a certain side—a sign that scar tissue has formed.

"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."

Raising Awareness Is Key to Better Endometriosis Treatment

Dr. Taylor said that taking a patient's pain seriously could save them years of frustrating misdiagnoses. It 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 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) lists a number of medications that may be tried, 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 get rid of 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."


While there are variations in staging the condition and the rASRM scale is still the most common classification system used, 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, it may cause significant pain or problems with fertility. There may also be DIE lesions present, even in the lower rASRM stages, affecting your quality of life.

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

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