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Endometriosis Stages & Types

Endometriosis is classified based on several factors, including the location, depth, size and amount of tissue. A patient’s specific type and stage can affect their symptoms as well as their chance of infertility. Types of endometriosis describe the area of the pelvis or abdomen affected by the disease, while the stages are used to describe the severity, depth and spread of the disease. Your treatment plan may be different depending on the stage and type with which you have been diagnosed.

Types of Endometriosis

There are three primary types of endometriosis: superficial peritoneal lesions, ovarian endometriomas and deep infiltrating endometriosis.2 The distinctions between these types are based on the location and type of growth. All three types of endometriosis can be associated with pelvic pain, but the location and extent of the lesions do not necessarily correspond with the severity of symptoms. 

  • Superficial Peritoneal Lesions: These thin, flat lesions involve the peritoneum, which is tissue that lines the abdominal wall and pelvic cavity. While these lesions are typically associated with mild cases of endometriosis, they can still be responsible for severe pain.
  • Ovarian Endometriomas (also known as Chocolate Cysts): Endometriomas are cysts that are commonly found on the ovaries and sometimes filled with brown fluid (chocolate cysts). Ovarian endometriomas are usually associated with more severe stages of endometriosis.
  • Deep Infiltrating Endometriosis (DIE): These lesions penetrate deep into the surface of the peritoneum, often causing severe pain. The presence of multiple deep implants indicates a later stage of endometriosis.

Endometriosis Stages

Endometriosis stages are classified according to the location, depth and spread of the disease. These classifications make up four stages that define the disease’s severity. Staging has been defined by the American Society for Reproductive Medicine1 (ASRM). Stage classifications are:



Stage 1


Stage 2


Stage 3


Stage 4


How Is the Stage Assigned?

Defining the stage of endometriosis involves evaluating specific criteria, including:

  • How far endometrial tissue has spread outside the uterus
  • The involvement of other organs in the pelvis
  • The presence and extent of pelvic adhesions, scar tissue that can bind organs together
  • The presence and size of ovarian endometriomas

The only way to identify the stage of endometriosis is during laparoscopic surgery. During a diagnostic laparoscopy, the surgeon will insert a small thin camera into the abdomen and inspect the entire pelvis. During this procedure, the severity of implants and adhesions are noted by the surgeon and scored using a points system. The number of points noted during the laparoscopy translates into one of the four main stages. A score of 15 or less puts the disease in stage 1 (minimal) or stage 2 (mild). A score of 16 to 40 translates to stage 3 (moderate), and a score of 40 or more is classified as stage 4 (severe). 

What Do the Stages Mean?

Stages of endometriosis correspond with the physical spread of the disease but do not necessarily align with severity of symptoms. It’s possible for a patient with stage 1 endometriosis to have debilitating pain while another patient with stage 4 endometriosis is completely asymptomatic. Symptoms are more often based on where endometriosis lesions are located. For example, lesions located on the bowel are more likely to cause bowel pain and discomfort.  Sometimes the only symptom of endometriosis is infertility. Progression through multiple stages of the disease may correlate with an increased risk of infertility over time, so classification is an important step for identifying risk.  

Stage 1 Endometriosis

Stage 1 endometriosis is classified as minimal. In this stage, there are few superficial implants and no significant adhesions or scar tissue. It is still possible to have severe symptoms in this stage despite the light spread of the disease.


stages endometriosis Stage 1

Stage 2 Endometriosis

Stage 2 endometriosis is classified as mild. In this stage, there can be both superficial and deeper implants, but still without any significant adhesions. 

stages endometriosis Stage 2

Stage 3 Endometriosis

Stage 3 endometriosis is classified as moderate. In this stage, there are multiple deep implants, small cysts on one or both ovaries and filmy adhesions. Adhesions are made up of scar tissue that causes organs to stick together. Adhesions can cause pain and nausea in some cases.

stages endometriosis Stage 3

Stage 4 Endometriosis

Stage 4 endometriosis is classified as severe. In this stage, there are multiple implants, large cysts on one or both ovaries and dense adhesions. Patients in this stage are at the highest risk of infertility and other complications, so treatment should be considered urgent. 

stages endometriosis Stage 4

Getting a Diagnosis

An endometriosis specialist can diagnose and treat the disease through minimally invasive laparoscopic surgery. If you have painful symptoms that you suspect may be caused by endometriosis, early diagnosis will bring you closer to relief.


For those who already have a confirmed diagnosis of endometriosis and are looking for long-term relief, our specialists can evaluate your case and recommend the best treatment option.