Endometriosis Types and Stages

Medically Reviewed by Traci C. Johnson, MD on November 12, 2022

Endometriosis is a condition where an endometrium-type tissue grows outside of the uterus. The endometrium is the tissue that lines the inside of the uterus. These growths are called endometrial implants.

They’re usually found in the pelvis or abdomen. They can grow on linings and organs, such as the fallopian tubes or ovaries. Like the endometrium, the tissue builds up and sheds with your menstrual cycle. But over time, the tissue that has been shed doesn’t have anywhere to go and becomes trapped. This can lead to inflammation, scarring, and cysts.

Experts group endometriosis by its stage and type. This is based on different things, such as the location, depth, size, and amount of tissue. What kind of endometriosis you have plays a role in your symptoms and the treatment.

What Are the Stages?

There are different ways to measure endometriosis. The most widely used scale is from the American Society of Reproductive Medicine. Doctors assign points according to the spread of the endometrial tissue, its depth, and the areas of your body that are affected.

Based on the results, the condition is ranked in one of four stages:

  • Stage 1 or minimal: There a few small implants or small wounds or lesions. They may be found on your organs or the tissue lining your pelvis or abdomen. There’s little to no scar tissue.
  • Stage 2 or mild: There are more implants than in stage 1. They’re also deeper in the tissue, and there may be some scar tissue.
  • Stage 3 or moderate: There are many deep implants. You may also have small cysts on one or both ovaries, and thick bands of scar tissue called adhesions.
  • Stage 4 or severe: This is the most widespread. You have many deep implants and thick adhesions. There are also large cysts on one or both ovaries.

Experts don’t know why some people have more severe cases than others. Endometriosis doesn’t always go from one stage to the next. If left untreated, it can remain the same over time. Or it may get worse or better.

What Are the Types?

Endometriosis is also grouped by what area of the pelvis or abdomen it affects. There are four main types:

  • Superficial peritoneal endometriosis. The peritoneum is a thin membrane that lines your abdomen and pelvis. It also covers most of the organs in these cavities. In this type, the endometrial tissue attaches to the peritoneum. This is the least severe form.
  • Endometriomas. These are dark, fluid-filled cysts. They’re also called chocolate cysts. They vary in size and can appear in different parts of your pelvis or abdomen, but they’re most common in the ovaries.
  • Deeply infiltrating endometriosis (DIE). In this type, the endometrial tissue has invaded the organs either within or outside your pelvic cavity. This can include your ovaries, rectum, bladder, and bowels. It’s rare, but sometimes a lot of scar tissue can bond organs so they become stuck in place. This condition is called frozen pelvis. But this only happens to 1%-5% of people with endometriosis.
  • Abdominal wall endometriosis. In some cases, endometrial tissue can grow on the abdominal wall. The cells may attach to a surgical incision, like one from a C-section.

What Are the Symptoms?

The main symptom is pain in your pelvis, usually during your period. You might also feel pain during sex, bowel movements, and when you pee. Other symptoms include heavy periods, fatigue, diarrhea, constipation, bloating, and nausea.

Most of the time, the stage and type of your condition doesn’t affect your symptoms. For example, a person with stage 1 endometriosis may have worse pain than someone with stage 4. The exception is infertility. Women with stages 3 or 4 are more likely to have trouble getting pregnant than those with stages 1 or 2.

How Are Types and Stages Diagnosed?

The only way to truly diagnose endometriosis is by laparoscopy. You’ll get general anesthesia for this surgery, so you’ll be asleep. A surgeon will make a small cut and insert a tiny, thin viewing tool through your stomach to look for signs of endometriosis. They may also take a small tissue sample, or biopsy, for testing. This will help rule out other causes.

Your doctor can only see superficial peritoneal endometriosis by laparoscopy. But before they orders the surgery, they will do other tests. They’ll do a pelvic exam to feel for a cyst, and they may order an ultrasound or MRI to look for an endometrioma.

Do Type and Stage Affect Treatment?

Doctors usually decide on your treatment based on your symptoms and whether you want to get pregnant. In most cases, you’ll start with pain medication. The doctor might also give you hormone therapy, like birth control pills, progestin therapy, aromatase inhibitors, and gonadotropin-releasing agonists and antagonists. Doctors used to think hormone therapy didn’t work for deeply infiltrating endometriosis, but recent research suggests that isn’t the case.

If these treatments don’t help, you may need surgery to remove the implants. This can be done by laparoscope or by abdominal surgery. Another option for women who don’t want to get pregnant is to surgically remove the uterus. This is called a hysterectomy. It could be paired with an oophorectomy, where the surgeon takes out your ovaries, too.

Show Sources


Tatnai L. Burnett, MD, FACOG, assistant professor of obstetrics and gynecology, Mayo Clinic.

Johns Hopkins Medicine: “Endometriosis.”

Mayo Clinic: “Endometriosis.”

UpToDate: “Endometriosis: Pathogenesis, Clinical Features, and Diagnosis.”

American Society for Reproductive Medicine: “Revised Classification for Endometriosis.”

Endometriosis Foundation of America: “Understanding the Different Stages of Endometriosis.”

American Journal of Roentgenology: “Abdominal Wall Endometriosis: Clinical Presentation and Imaging Features with Emphasis on Sonography.”

Brigham and Women’s Hospital: “Deeply Infiltrative Endometriosis.”

European Journal of Obstetrics, Gynecology, and Reproductive Biology: “Surgery Versus Hormonal Therapy for Deep Endometriosis: Is It a Choice of The Physician?”

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