Endometriosis Stages 1 to 4: What They Mean and What They Miss

Endometriosis has 4 stages: stage 1 (minimal), stage 2 (mild), stage 3 (moderate) and stage 4 (severe). A surgeon gives the stage during surgery, from a points score for where the endometriosis is, how large and how deep it is, and how bad the adhesions are.

The most important thing to know is that the stage does not tell you how much pain you have. In a study of more than 1,000 people who had surgery, the link between stage and how bad the pelvic pain was was very small and not consistent. A person with stage 1 can have severe pain.

This guide explains each stage, how a doctor finds it, the other systems you may hear about, and what the stage means for fertility and treatment. It is general information and not medical advice.

The 4 endometriosis stages at a glance

The stage system most doctors use is the revised American Society for Reproductive Medicine (rASRM) classification. The surgeon adds up points for what they see, and the total gives the stage. These are the point ranges for each stage:

Points come from endometriosis on the lining of the pelvis and on the ovaries, adhesions on the ovaries and fallopian tubes, and whether the spots are superficial or deep. Adhesions are bands of scar tissue that can stick organs together.

The words "minimal" and "severe" describe what the surgeon saw. They do not describe your pain, your quality of life or how serious the disease feels to you.

What each stage means

Stage 1: minimal

The total is 1 to 5 points, the lowest score. It usually means a small amount of endometriosis on the surface of the pelvis. Superficial spots are the type that a normal scan does not rule out, so stage 1 may only show at surgery. Stage 1 can still cause severe pain.

Stage 2: mild

The total is 6 to 15 points. The surgeon found more endometriosis than in stage 1, or some of it was deep rather than on the surface, because deep spots score more points.

Stage 3: moderate

The total is 16 to 40 points. An endometrioma is a cyst on the ovary filled with old blood, also called a chocolate cyst. An endometrioma larger than 3 cm scores 20 points on its own, which is enough to reach stage 3. Dense adhesions on an ovary or tube also score high.

Stage 4: severe

The total is more than 40 points. The surgeon found a lot of endometriosis, endometriomas, adhesions, or a mix of these. When the space between the uterus and the rectum is fully closed by adhesions (complete cul-de-sac obliteration), that one finding scores 40 points and counts as severe disease.

How endometriosis staging is done

The rASRM stage needs surgery. The surgeon does a laparoscopy (keyhole surgery), looks at the pelvis with a small camera, and adds up the points from what they see. They can treat the endometriosis in the same operation, and a lab checks the removed tissue to confirm the diagnosis. If you have a laparoscopy coming up, our laparoscopy preparation and recovery guide explains what happens on the day.

The stage is not always exact. When surgeons score the same person again, the stage can change. This is because the score depends on what the surgeon sees and how they judge it.

What imaging can and cannot show

Before surgery, doctors use ultrasound or MRI. A scan can show an endometrioma or deep endometriosis, and doctors can use it to plan surgery. But a normal scan does not rule out endometriosis, especially the superficial spots of stage 1 and 2. If your scan is normal and treatment has not helped, your doctor may offer a laparoscopy to find and treat the disease.

A scan can give a good idea of what is there, but it does not give an rASRM stage. For the full path to a diagnosis, see how to get diagnosed with endometriosis.

Write down your symptoms and your questions before the visit where your doctor talks about your stage.

Other endometriosis classification systems

The rASRM stage is not the only system. There are 22 published systems, each made for a different purpose, and doctors do not yet agree on one. You may see these three in a surgery report or a fertility clinic letter.

#Enzian: for deep endometriosis

The rASRM stage does not count deep endometriosis in places such as the bladder, the vagina, the bowel and the ligaments behind the uterus. #Enzian fills this gap. It maps where the deep endometriosis is and how large it is, and the 2021 version also covers the ovaries and the lining of the pelvis. A doctor can use #Enzian with MRI or ultrasound before surgery to plan the operation. If you have bowel symptoms, see our guide to bowel endometriosis symptoms.

The Endometriosis Fertility Index (EFI)

The EFI is for people who want to get pregnant. It gives a score from 0 to 10 from your age, how long you have tried to get pregnant, past pregnancies and how well the tubes and ovaries work at surgery. A higher score means a better chance. The EFI predicts the chance of a natural pregnancy after surgery well, which the rASRM stage does not do.

The 2021 AAGL classification

This newer system gives 4 stages that are built to match how complex the operation is. It tells the difference between simple and complex surgery better than the rASRM stage. Its link with pain and infertility is about the same as the rASRM stage.

What the stage means for fertility

A higher stage can mean more damage to the ovaries and tubes, but the stage alone is a weak guide to your chances. The rASRM stage has a poor link with fertility outcomes. The EFI is a better tool for this question.

The stage can still change the plan. In stage 1 or 2, surgery to remove endometriosis can raise the chance of an ongoing pregnancy, and IUI with fertility drugs can also help. IVF is an option at any stage, especially if the tubes do not work well. Ask your fertility doctor what your stage and your EFI score mean for you.

What the stage means for treatment

Treatment depends on your symptoms, your scan and surgery findings and your plans for pregnancy, not on the stage number alone. For a comparison, see our guide to endometriosis treatment options.

For surgery, where the endometriosis is matters more than the stage. Deep endometriosis on the bowel or bladder can make the operation more complex, and people with deep endometriosis should be referred to a centre of expertise. Our guide to excision and ablation surgery explains the two main ways to remove endometriosis.

Why a low stage can still mean severe pain

A stage 1 or 2 result does not mean your pain is small or "in your head". The link between stage and pain is weak, and no staging system has been shown to match pain or quality of life.

The type and place of the endometriosis matter more than the total. For example, endometriosis behind the uterus has a strong link with pain during sex. Your pain is real at any stage. If a doctor uses a low stage to dismiss your symptoms, it is fine to ask for a second opinion or a referral to an endometriosis specialist.

When to get help now

Get emergency care at once if you have sudden, severe pain in your belly or pelvis, pain with a fever, vomiting, or you feel faint. Tell the staff that you have endometriosis.

What to track before the visit where your stage is discussed

The stage tells your doctor what the surgeon saw. Your notes tell them how you live with it. Together, they help you and your doctor choose treatment. A diary helps to show your doctor your pain in clear terms. Write down:

• Pain. How bad it is from 0 to 10, where it hurts and on which days.
• Period days. The first day of each period and how heavy the flow is.
• Pain with sex, peeing or pooing. Which day and how bad.
• Bowel and bladder changes. Constipation, diarrhoea, bloating or pain when you pee.
• Tiredness. Days when fatigue stops you from doing normal things.
• Medicines. What you took, how often and whether it helped.
• Fertility plans. If you want to get pregnant, and how long you have tried.

Then bring these questions:

• What stage did you find, and where was the endometriosis?
• Did you find deep endometriosis or an endometrioma?
• Did you remove the endometriosis, and did the lab confirm it?
• If I want to get pregnant, what is my EFI score?
• What treatment do you suggest now, and why?

Endolog is a pain and symptom diary for endometriosis. You log pain severity, where it hurts, bleeding, digestive, bowel and urinary symptoms, fatigue and flare notes on the days they happen, so you have a clear record for your visit. For a paper version, print the free pain diary.

Frequently asked questions

What are the 4 stages of endometriosis?

Stage 1 is minimal, stage 2 is mild, stage 3 is moderate and stage 4 is severe. A surgeon sets the stage from a points score at surgery.

Can you know your endometriosis stage without surgery?

Not exactly. The rASRM stage needs a laparoscopy. An ultrasound or MRI can show an endometrioma or deep endometriosis, but a normal scan does not rule out endometriosis.

Does a higher stage mean more pain?

Not reliably. The link between stage and pain is small and not consistent. Some people with stage 1 have severe pain.

Is stage 4 endometriosis cancer?

No. "Severe" is a measure of how much endometriosis the surgeon saw. Endometriosis is not cancer. It raises the risk of some cancers a little, but the risk for each person stays low.

Can you get pregnant with stage 4 endometriosis?

It can be possible. Stage 4 can make it harder, and IVF is an option, especially if the tubes do not work well. A fertility doctor can use the EFI to estimate your chance.

This article is for general information. It is not medical advice and does not replace advice from your own doctor, who decides what treatment is right for you. If you think you have an emergency, call 911.