Endometriosis is a chronic condition where lesions, consisting of tissue similar to the uterine lining, grow outside of the uterus. It’s estimated to impact 10 to 15 percent of women of reproductive age.

Endometriosis can be divided into several different stages. These are based on factors like the number, location, and severity of endometriosis lesions.

In this article, we’ll take a closer look at the types of endometriosis lesions as well as endometriosis staging and whether endometriosis lesions can be removed.

The lining of your uterus is called the endometrium. During your menstrual cycle, the endometrium thickens in order to prepare for the implantation of a fertilized embryo. If this doesn’t happen, the endometrium is shed during your period.

Endometriosis lesions are patches of tissue that are similar to the endometrium. But unlike the endometrium, they grow in areas outside the uterus.

These lesions also thicken during your menstrual cycle and bleed during your period. However, because this tissue cannot leave your body, it can lead to the common symptoms of endometriosis, such as pain, swelling, and digestive problems.

Endometriosis lesions can vary in size and often appear as nodules or cysts. They’re mostly brown, black, or blue in color. However, they can also sometimes be red, white, or clear.

It’s also possible for endometriosis lesions to be associated with adhesions. Adhesions are bands of scar tissue that can cause organs and tissues in the pelvis to stick together.

Where are endometriosis lesions found?

The most common areas for endometriosis lesions to be found are the:

  • ovaries
  • fallopian tubes
  • outside surface of the uterus
  • ligaments surrounding the uterus

It’s also possible for endometriosis lesions to be found in other areas of the pelvis, such as the:

While endometriosis lesions mainly affect organs and tissues in the pelvis, they can, in rare instances, be detected in other areas. A few examples include the liver, lungs, or brain.

There are three different types of endometriosis lesions. These are generally categorized based on the area where they occur. It’s possible to have multiple types of endometriosis lesions at one time.

Superficial peritoneal lesions

Superficial peritoneal lesions are found on the peritoneum. This is the tissue that lines the pelvic cavity and organs. It’s the most common type of lesion, and accounts for about 80 percent of endometriosis lesions.


Endometriomas are a type of cyst that most often appear on the ovaries, although they can, in some instances, appear on other tissues as well.

It’s estimated that between 17 and 44 percent of people with endometriosis will have an endometrioma.

With an endometrioma, the endometriosis tissue bleeds into the cyst, leading to accumulation of a brown fluid. For this reason, endometriomas are often referred to as chocolate cysts.

Deep infiltrating endometriosis (DIE)

Deep infiltrating endometriosis (DIE) refers to endometriosis lesions that penetrate 5 millimeters (mm) or more into the affected tissue. It’s estimated to affect about 20 percent of individuals with endometriosis.

DIE is the most aggressive form of endometriosis and is often associated with severe symptoms. The main areas where DIE can occur include the:

  • ligaments surrounding the uterus
  • tissue between the uterus and rectum (pouch of Douglas)
  • area of the vagina known as the posterior fornix
  • tissue separating the vagina and rectum (rectovaginal septum)
  • urinary tract, including the bladder and ureters
  • intestines

Diagnostic laparoscopy is the only sure way to know if you have endometriosis. Laparoscopy uses an instrument called a laparoscope to examine the organs and tissues of your pelvis. It’s a minimally invasive surgery that only uses small incisions.

This procedure often involves the collection of a biopsy sample from an endometriosis lesion. The biopsy sample is then carefully examined in a laboratory.

Other imaging techniques, such as ultrasound or magnetic resonance imaging (MRI), may also be used during diagnosis and for planning treatment.

Doctors can use the information gained from a diagnostic laparoscopy to stage endometriosis.

The American Society for Reproductive Medicine (ASRM) staging system

The American Society for Reproductive Medicine (ASRM) criteria is most often used to stage endometriosis. This uses a scoring system to evaluate:

  • the presence of endometriosis lesions affecting the peritoneum, ovaries, and fallopian tubes
  • how deeply endometriosis lesions penetrate the surrounding tissue
  • whether adhesions are present and how dense they are

With the ASRM criteria, higher scores are associated with more extensive endometriosis. There are four different stages:

  • Stage I (minimal). Individuals with stage I endometriosis typically have a few superficial endometriosis lesions.
  • Stage II (mild). In stage II endometriosis, more lesions are observed, and they typically penetrate deeper into the affected tissue.
  • Stage III (moderate). People with stage III endometriosis often have:
    • a large number of deep endometriosis lesions
    • smaller endometriomas on one or both ovaries
    • some adhesions
  • Stage IV (severe). Those with stage IV endometriosis typically have:
    • a large number of deep endometriosis lesions
    • large endometriomas on one or both ovaries
    • many dense adhesions

The stage of endometriosis doesn’t always correlate with symptom severity. It just reflects how extensive endometriosis is. For example, it’s possible to have stage II endometriosis and still experience severe pain and swelling.

The Enzian classification

One of the drawbacks of the ASRM system is that it does not account for the presence of deep infiltrating endometriosis (DIE), which affects tissues other than those included in the ASRM system.

The Enzian classification system was developed to describe the extent of DIE in a person with endometriosis. It takes the following factors into account:

  • Location. There are 3 separate compartments, each classified by a letter.
    • Compartment A includes the vagina and the pelvic space between the vagina and the rectum.
    • Compartment B includes the pelvic wall and the ligaments of the pelvis.
    • Compartment C includes the colon and rectum.
  • Level. The level criterion is how far the endometriosis lesions penetrate the affected tissues. There are 3 levels:
    • Level 1 is less than 1 centimeter.
    • Level 2 is 1 to 3 centimeters.
    • Level 3 is greater than 3 centimeters.
  • Other affected organs. This accounts for the involvement of additional organs, including the:
    • bladder
    • ureters
    • intestines
    • organs outside of the pelvis

A 2013 study evaluated the Enzian system in 194 people with endometriosis. A correlation between more severe Enzian classification and more severe ASRM score was found.

Also, symptoms like pain and severe menstrual cramps were associated with a more severe Enzian classification.

The Endometriosis Fertility Index (EPI)

Another drawback of the ASRM system is that it does not reflect how endometriosis can affect your fertility. This is often an important concern for people with endometriosis who want to get pregnant.

The Endometriosis Fertility Index (EPI) was developed to help describe the likelihood of becoming pregnant. It uses a variety of factors, including:

  • the estimated function of the ovaries, fallopian tubes, and fimbria
  • personal information like age, number of years you’ve experienced infertility, and history of prior pregnancies
  • the score from the ASRM system

A 2018 study assessed the EPI in predicting the ability to conceive without in vitro fertilization (IVF).

It found that the EPI was better than the ASRM system at predicting the likelihood of conceiving, regardless of whether an individual has endometriosis.

As we mentioned earlier, a surgical diagnosis using laparoscopy is very important in determining if you have endometriosis. Once a diagnosis of endometriosis has been confirmed, it’s also possible for endometriosis lesions to be removed using surgery.

Undergoing surgery to remove endometriosis lesions is typically recommended if more conservative treatments haven’t provided relief or you’re experiencing infertility due to endometriosis.

Endometriosis surgery is often performed using a laparoscope. During the procedure, the surgeon works to locate endometriosis lesions. They’ll then destroy or remove them. This type of surgery preserves your fertility.

There are two different types of laparoscopic surgery for endometriosis – excision and ablation.

During excision, the surgeon carefully cuts away the endometriosis lesions. During ablation, endometriosis lesions are destroyed using things like heat, freezing, or a laser beam. Excision is generally more effective at relieving symptoms.

Hysterectomy can also be used to remove endometriosis lesions, particularly those affecting the outside of the uterus and surrounding tissues like the ovaries. This surgery involves the removal of the uterus and can also include removal of the ovaries, fallopian tubes, or both. This is typically a last resort option, as you’ll no longer be able to become pregnant afterward.

A recurrence of endometriosis lesions is fairly common after surgery. The recurrence rate after surgery has been estimated to be between 6 and 67 percent, although the rate can depend on several factors like the type of surgery and endometriosis lesions.

Some evidence shows that excision has lower recurrence rates in women with endometriosis that’s a lower ASRM stage.

Overall, deciding to have surgery for endometriosis is a big decision. It’s important to discuss all the risks and benefits of surgery with your doctor before deciding to have a procedure.

Other treatments for endometriosis

If surgery is not an option for you, there are other endometriosis treatments that may help, such as:

  • Medications. Several different types of medications may help curb the symptoms of endometriosis. These include:
    • gonadotropin-releasing hormone (GnRH) agonists, which halt the production of hormones important for your menstrual cycle, leading to a temporary menopause
    • over-the-counter (OTC) medications like ibuprofen (Advil, Motrin), naproxen (Aleve), and acetaminophen (Tylenol), which may be helpful for mild pain or swelling due to endometriosis
  • Complementary and alternative medicine (CAM). Some people report that CAM therapies like herbs and supplements, acupuncture, or massage therapy help ease their symptoms.
  • Lifestyle changes. Implementing lifestyle changes may also help ease the symptoms of endometriosis. This can include:
    • seeking support from friends and family or through a support group or mental health professional

You may need to use several types of treatment to help with endometriosis. Also, you may need to try out different combinations of treatments before you find what works best for you.

Endometriosis causes lesions that consist of tissue like the lining of your uterus to appear in places where they do not belong. This can lead to symptoms like pain, swelling, and digestive problems. Endometriosis can also affect fertility.

The most common areas for endometriosis lesions to occur are on or around the uterus and ovaries. However, they can also impact the vagina, intestines, and urinary tract as well.

Endometriosis is staged according to the number, location, and severity of endometriosis lesions. However, the stage of your endometriosis won’t always reflect the severity of your symptoms.

In some situations, surgery may be recommended to remove endometriosis lesions. When surgery is not an option, medications, CAM therapies, and lifestyle changes may help alleviate the symptoms of endometriosis.