What Are the 4 Stages of Endometriosis? (Understanding Your “Score”)
If you have had a laparoscopy, you likely woke up to a number: “You have Stage 2” or “You have Stage 4.”
But this number can be confusing. We often see patients with Stage 1 disease who are in agonizing, daily pain, while some patients with Stage 4 have no pain at all and only discover the disease during fertility testing.
The staging system most commonly used—created by the American Society for Reproductive Medicine (ASRM)—was originally designed to predict fertility, not pain. It scores the disease based on the amount of tissue, not the location relative to nerves.
Here is what the 4 stages actually look like inside the pelvis.
Stage 1: Minimal
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The Look: Small, isolated implants or “spots” of endometriosis. They look like shallow blisters or powder burns on the surface of the peritoneum (the lining of the pelvis).
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Adhesions: None or very minimal filmy scar tissue.
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The Reality: Do not let the word “Minimal” fool you. These superficial lesions are often highly active biologically, releasing a storm of inflammatory cytokines (pain chemicals). Because they are “fresh,” they can be more painful than older, scarred-over lesions.
Stage 2: Mild
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The Look: More implants are present, and they may be deeper than in Stage 1.
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Adhesions: You might have some mild scarring, but no major organs are glued together.
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The Reality: “Mild” refers to the volume of disease, not the symptom severity. A single Stage 2 nodule sitting on the uterosacral ligament can cause excruciating pain during sex or bowel movements.
Stage 3: Moderate
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The Look: This is a significant jump in severity. It typically involves ovarian endometriomas (chocolate cysts)—cysts filled with old blood that form on the ovary.
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Adhesions: More distinct scarring is present. You may have filmy or dense adhesions beginning to distort the anatomy, perhaps pulling the ovary toward the pelvic sidewall.
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The Reality: Once cysts form, the disease is considered advanced. The toxic fluid inside the cysts can damage ovarian reserve, making fertility preservation a priority.
Stage 4: Severe
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The Look: This is the most extensive form. It involves large, deep cysts on one or both ovaries and many deep implants.
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Adhesions: This stage is characterized by dense adhesions (thick scar tissue). The pelvic anatomy is often completely distorted. This can lead to a “Frozen Pelvis,” where the uterus, ovaries, tubes, and bowel are fused together into a single, immobile block.
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The Reality: While often associated with infertility, Stage 4 requires the highest level of surgical skill to restore anatomy safely without damaging the bowel or ureters.
Moving Beyond the Old System: The Contribution of Dr. Mauricio Abrao
The ASRM staging system has a major blind spot: It does not account for Deep Infiltrating Endometriosis (DIE) or surgical complexity. You can have a deep nodule on your bowel causing severe organ dysfunction, but if your ovaries look “okay,” you might technically be staged lower.
Recognizing this critical gap, Dr. Mauricio Abrao, a world-renowned leader in endometriosis from Brazil and a key mentor within the ESSI network, spearheaded the effort to modernize how we classify this disease.
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The AAGL 2021 Classification: Dr. Abrao led the development of the AAGL 2021 Endometriosis Classification, a new system designed to correlate surgical complexity with patient outcomes.
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Why it Matters: Unlike the old system, Dr. Abrao’s work helps surgeons predict exactly how difficult a surgery will be before they enter the operating room, ensuring that complex cases are matched with expert excision teams.
This is why at ESSI, we don’t just treat the “Stage”—we treat the patient. Thanks to pioneers like Dr. Abrao, we now have better tools to understand your disease and plan the safest, most effective surgery.
