What Are the 4 Stages of Endometriosis?

Reviewed on 4/15/2021

There are four stages of endometriosis, a condition that causes abnormal tissue to grow outside of the womb, that range from mild endometriosis to severe endometriosis. The severity of symptoms does not necessarily indicate the stage of endometriosis.
There are four stages of endometriosis, a condition that causes abnormal tissue to grow outside of the womb, that range from mild endometriosis to severe endometriosis. The severity of symptoms does not necessarily indicate the stage of endometriosis.

Endometriosis is a common condition in which tissue similar to the lining of the uterus (the endometrium) grows outside the womb and can cause pelvic pain and difficulty getting pregnant. It most commonly occurs in the ovaries, fallopian tubes, the bowel, and the areas in front, in back, and to the sides of the uterus.

The American Society of Reproductive Medicine classifies endometriosis into 4 stages, based on the location, amount, depth, and size of endometrial tissue:

Stage Description

Stage 1: Minimal

  • Superficial lesions are present
  • Lesions do not penetrate deeply and are mostly located within the lining of the abdominal cavity (peritoneum)
Stage 2: Mild
  • More lesions and ovarian endometriomas are present

Stage 3: Moderate
  • There is a range of deep infiltrating endometriosis lesions, endometriomas, and adhesions

Stage 4: Severe

  • Lesions penetrate deeply, significant scar tissue or adhesions and large ovarian cysts are present
  • Endometriosis can be found in other parts of the body including the bowel, bladder, and rarely, the lungs

The stage of endometriosis is not always indicative of pain levels. A woman with stage 1 endometriosis can have severe pain, while a woman who has state 4 endometriosis may have minimal to no pain. However, women with more severe disease do have more problems with infertility.

What Are Symptoms of Endometriosis?

Endometriosis may not cause any symptoms in some women. When symptoms occur, they may be serious and can include: 

  • Pelvic pain
    • Can be severe in some cases
    • Frequently just before or during menstrual periods
    • May occur between menstrual periods and worsen during a period
    • Period pain may get worse over time
    • With bowel movements or while urinating, especially during a period
    • During or after sex
  • Infertility 
  • Ovarian cysts that contain endometriosis tissue (endometriomas)
    • Usually filled with old blood resembling chocolate syrup, sometimes referred to as “chocolate cysts”
    • Cysts are benign (not cancerous) but may also cause pelvic pain

Endometriosis symptoms usually go away when a woman goes through menopause.


Endometriosis occurs deep inside the uterus. See Answer

What Causes Endometriosis?

The cause of endometriosis is unknown but there are a number of theories as to why the condition develops:

  • Metaplasia occurs when one type of tissue changes to another normal type of tissue. One theory is that endometrial tissue may have the ability to replace other types of tissues outside the uterus.
  • First-degree relatives of women who have endometriosis are more likely to develop the disease, which means there may be a genetic predisposition.
  • Immune system dysfunction may play a role. 
  • Endometrial fragments may travel through blood vessels or the lymphatic system to other parts of the body, which could explain how endometriosis cells end up in distant parts of the body, such as the lung, brain, skin, or eye.
  • Retrograde menstruation is an older theory that supposes menstrual tissue flows backwards through the fallopian tubes (called “retrograde flow”) and deposits on the pelvic organs where it grows, however, researchers have found 90% of women have retrograde flow and do not have endometriosis, so it is believed something else (such as immune system or hormonal dysfunction) triggers endometriosis.
  • Environmental factors may contribute to the development of endometriosis, such as the effects of toxins in the environment on reproductive hormones and immune system function. This theory is controversial.

How Is Endometriosis Diagnosed?

There is no single simple test to diagnose endometriosis, and it is difficult to diagnose. Diagnosis is additionally complicated because many women are brought up to believe pelvic pain and other symptoms are normal, and often birth control hormones or pregnancy can temporarily relieve symptoms even without a diagnosis.  

The only way to definitively diagnose endometriosis is with an invasive laparoscopic procedure and a biopsy of the tissue. The procedure may also be used to remove endometriosis at the same time. 

Endometriomas (ovarian cysts containing endometriosis tissue) may be seen with ultrasound

It is important for women to find a doctor experienced in treating endometriosis, because a common problem among patients with endometriosis is having a healthcare provider take the pain seriously. 

What Is the Treatment for Endometriosis?

Endometriosis symptoms usually go away when a woman goes through menopause.

Treatment of endometriosis pain may include several different modalities, including medication, therapy, trigger point and nerve injections, and laparoscopic surgery.

Medications used to treat endometriosis include:

Interventional therapies used to treat endometriosis pain include:

  • Nerve blockade
  • Anesthetic muscle injections with or without corticosteroids to block trigger points
  • Physical therapy to help control and relax pelvic muscles
  • Behavioral therapy to help manage stress and pain
  • Acupuncture

Surgery for endometriosis is done both to diagnose endometriosis and also to remove it. It may be performed before medications are tried since it’s used diagnostically. It may also be considered if medications do not work to relieve pain. 

  • Endometriosis surgery is often done laparoscopically, which is less invasive than open surgery. The goal of surgery is to remove endometriosis and scar tissue, but it is not a permanent cure and endometriosis tissue often grows back and pain returns without post-surgical treatment such as hormonal birth control.
  • Surgery for endometrioma (ovarian cysts containing endometriosis tissue) is usually only done if the cyst is larger than 4 to 5 cm, symptomatic, or is growing.
  • Removal of the uterus (hysterectomy), ovaries (oophorectomy), or ovaries and fallopian tubes (salpingo-oophorectomy) is the only permanent treatment and may be recommended for patients who:
    • Have tried other treatments and still have severe symptoms
    • Do not wish to become pregnant in the future
    • Want a permanent treatment 

Endometriosis can also cause infertility. Treatments for infertility related to endometriosis include:

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Reviewed on 4/15/2021