4 Stages of Endometriosis and What They Can Mean

With endometriosis, the cells that are similar to the tissue that normally lines the inside of the uterus grow outside of the uterus. These cells are known as the endometrium. Lesions of abnormal tissue may shed and become inflamed or cause cysts and scar tissue. As a result, people with endometriosis may have painful and heavy menstrual bleeding, among other painful symptoms.

Most commonly, endometriosis grows on the surface of the uterus, the pelvic floor, fallopian tubes and ovaries. But lesions can also spread to the intestines and rectum.

Healthcare providers stage the condition depending on the location, size, and depth of those lesions. The American Society of Reproductive Medicine (ASRM) defines four stages in one of the most widely used systems. If you have endometriosis, defining your stage can help plan your treatment.

Here's what you should know about the ASRM's staging system and other staging systems that healthcare providers may use to describe endometriosis.

The ASRM Stages of Endometriosis

The ASRM provides a booklet that describes endometriosis and its staging process. Also, the ASRM provides an overview of key terms and what each stage, which ranges I–IV, means. But understanding the staging system also means considering its limitations.

Key Terms Involved in the I–IV Staging System

The ASRM defines the following terms:

• Endometriosis implants: These are endometrial cells, which typically grow inside of the uterus, that grow and spread outside of the uterus. Endometrial lesions are generally small and flat.
• Endometrial adhesions: These are clusters of fibrous tissue that form in bands. Endometrial adhesions can bind organs together. Typically, those include the abdominal and pelvic organs. A study published in 2019 in the International Journal of Fertility and Sterility explained that endometrial adhesions form as part of an inflammatory process.
• Ovarian endometriomas: Also known as chocolate cysts, these blood-filled cysts turn brown over time. The cysts grow on the ovaries endometrial cells spread and grow there.

Four Stages of Endometriosis

Per the ASRM, the I–IV staging system is a point system. The stage of endometriosis depends on the following:

• The location, extent, and depth of implants
• The presence and severity of adhesions
• The presence and size of ovarian endometriomas

Healthcare providers give points for each category. The higher the points, the higher the stage. Also, an article published in 2018 in Cureus defines the point ranges for each stage.

• Stage I: This is also known as minimal endometriosis. In stage I, superficial implants and mild adhesions may grow outside the uterus. The point score for minimal endometriosis is between one to five.
• Stage II: This is also known as mild endometriosis. With stage II, the implants may be superficial or deep, with mild adhesions. Endometriosis may be widespread in stage II, and deep implants may be present. The point score for mild endometriosis is six to 15.  
• Stage III: This is also known as moderate endometriosis. With stage III, deep implants are present. Also, adhesions may be dense instead of filmy and thin. As a result, endometriosis is more widespread than in Stage II. The point score for moderate endometriosis is between 16–40.  
• Stage IV: This is also known as severe endometriosis. With stage IV, deep implants and dense adhesions are present. There may be superficial endometriosis and filmy adhesions, but the disease is more widespread than in Stage III. Any score greater than 40 indicates severe endometriosis.

Limitations of the ASRM Endometriosis Staging System

The escalating severity of the ASRM staging system might indicate that endometriosis starts in one part of the body before spreading to more distant organs. But endometriosis can be widespread from the start, Hugh Taylor, MD, vice president of the ASRM, 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," said Dr. Taylor. "But this is not the same type of staging system that would have meaningful prognostic value, like in cancer."

Also, the four stages don't correlate to how much factors like infertility or pelvic pain affect people. So, while defining the stage can help guide treatment, it isn't the only key factor in treatment.

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

Endometriosis Diagnosis

Laparoscopy is the only way to confirm endometriosis. During laparoscopy, the healthcare provider can also evaluate the extent of endometriosis and stage it. 

A healthcare provider makes small incisions in the pelvic region, then inserts a small instrument called a laparoscope. A laparoscope has a small camera on the end of the device, allowing the healthcare provider to see any endometrial implants or adhesions. The healthcare provider can also obtain a sample for biopsy.

Also, the healthcare provider may evaluate fertility by seeing if the fallopian tubes are open. Specifically, the healthcare provider injects a special dye and sees if the dye goes through the fallopian tubes.

How To Treat Endometriosis

Treatment depends on your symptoms and reproductive goals. Some of the most common treatments for endometriosis include:

• Laparoscopy: This diagnostic tool can also treat endometriosis by removing lesions, scar tissue, and cysts. The surgery may also reduce pain and preserve fertility. But many people experience a return of their symptoms within a few years.  
• Hormonal birth control: Pills, patches, or vaginal rings can help alleviate painful menstrual bleeding. Those hormonal birth control methods employ estrogen and progesterone hormones to control or stop the menstrual cycle. 
• Gonadotropin-releasing hormone (GnRH) agonists: These medications block estrogen, preventing your menstrual cycle. But GnRH agonists often come with adverse side effects, similar to symptoms seen in menopause.
• Non-steroidal anti-inflammatory drugs (NSAIDs): Medicines like Advil (ibuprofen) can also help with the pain. 
• Fertility treatments: Lesions may distort the structure of reproductive organs, such as the fallopian tubes. In that case, becoming pregnant can be difficult. Fertility treatments like in vitro fertilization (IVF) may be the best option if your primary concern is infertility.
  

Other Methods of Staging Endometriosis

Researchers have devised other ways to classify endometriosis that recognize painful symptoms. For example, in a study published in 2017 in Human Reproduction, researchers stressed the need for a global consensus on how to classify endometriosis. The researchers pointed out that staging endometriosis ought to consider the views of people with the condition.

ENZIAN Scale

A study published in 2020 in Global Reproductive Health described the ENZIAN scale, which takes into account painful symptoms. The ENZIAN scale includes eight "compartments," based on the location of the endometrial lesions, which include:

• 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 ENZIAN scale also considers the severity and size of lesions. Based on the size of lesions, healthcare providers can assign one of the following grades:

• Grade 1: Less than one centimeter
• Grade 2: One to three centimeters
• Grade 3: Greater than three centimeters

Per the researchers, the ENZIAN scale may help correlate pain felt with the severity of symptoms. For example, an A1 classification indicates endometriosis in the vagina and rectovaginal septum. Also, the lesions are less than one centimeter in size.

The researchers urged healthcare providers to use the ENZIAN scale with the ASRM's staging system to provide a clear diagnosis. 

Descriptive Classifications of Endometriosis

According to Tamer Seckin, MD, a gynecologist, laparoscopic surgeon, and endometriosis specialist, healthcare providers can also stage endometriosis using descriptive classifications. Those classifications, which depend on the location and severity of lesions, include:

• Peritoneal endometriosis: Lesions grow on the peritoneum, a membrane that lines the abdomen. 
• Ovarian endometriomas: Endometriomas in the ovaries may burst and spread lesions to other nearby organs.
• Cul-de-sac obliteration: Endometriosis has infiltrated organs in the pelvic region. Typically, cul-de-sac obliteration affects the rectum and the outside of the uterus.
• Deep infiltrating endometriosis: The condition has become invasive. Lesions penetrate other organs, such as the bladder or bowel wall.
• Frozen pelvis: Lesions deeply infiltrate the pelvic ligaments, nerves, and muscle tissue. Nearby organs may become "cemented" or frozen.

Delays in Endometriosis Diagnosis

People may experience lengthy diagnostic delays when it comes to endometriosis. On average, it may take nearly seven years to confirm a diagnosis. Diagnostic delays lead to delayed treatment options and unnecessary pain.

There are several factors contributing to diagnostic delays, which include:

• The perception of some symptoms, such as painful periods, as normal 
• Embarrassment discussing reproductive health with healthcare providers 
• Tolerance of symptoms

One classic sign of endometriosis is pelvic pain. Some people with endometriosis have pelvic pain that occurs outside of their periods. Others may have intense cramps during their periods that prevent them from going to school or work. But often, painful periods are considered "normal."

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

So, to reduce the time it takes to diagnose and treat endometriosis, some healthcare providers may clinically recognize signs without needing surgery, said Dr. Taylor.

Laparoscopy is the gold standard when it comes to endometriosis diagnosis. But other diagnostic methods may suggest the likelihood of endometriosis. For example, a pelvic exam may indicate large cysts or scar tissue behind the uterus. Imaging, such as an ultrasound or magnetic resonance imaging (MRI), can also look for cysts.

Taking a person's pain seriously could save years of frustrating misdiagnoses, said Dr. Taylor. Early diagnosis and treatment could also curb symptoms sooner, reducing pain and debilitating scar tissue.

A Quick Review

There are several ways to stage endometriosis. The ASRM's four stages scale is one of the most used methods to classify the condition. But researchers have also pointed out that considering painful symptoms and quality of life is key.

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