The stages of endometriosis

The uterus, also called the womb, is a pear-shaped female reproductive organ located between the bladder and rectum. The uterus is muscular and lined with tissue. This lining inside the uterus is where a fertilized egg attaches when a person becomes pregnant. This lining is also what is shed during menstruation, when there is no pregnancy.

Endometriosis is a disorder that affects women of reproductive age. It involves tissue that is similar to the tissue that lines the womb. When a woman has endometriosis, this tissue grows outside the womb. These patches of tissue are called implants. Most often, endometrial implants occur on sites in the pelvic area—the outer surface of the uterus, the ovaries, and the fallopian tubes, as well as the bowel. Endometrial implants can also occur in more distant sites, though this is rare.

Symptoms of endometriosis can include:

• Painful periods
• Heavy menstrual bleeding
• Pain during sex
• Nausea
• Bladder symptoms
• Diarrhea and/or constipation
• Bloating
• Fatigue
• Lower abdominal pain
• Lower back pain

Endometriosis has also been associated with fertility problems.

Stages of endometriosis

If you are researching endometriosis, you will likely come across the phrase “stages of endometriosis.” This comes from a classification system developed by the American Society of Reproductive Medicine (ASRM). This system classifies endometriosis into stages based on:

• The amount of endometrial tissue present
• Whether implants are superficial or deep
• The density of the endometrial adhesions
• The pelvic organs and structures that are affected

Adhesions are bands of scar tissue that can form between structures inside the pelvis that are not normally connected and should usually glide against one another. For example, an adhesion can bind an ovary to the pelvic wall, which can result in significant pain and damage to the ovaries. Adhesions that are described as “filmy” are thin and transparent. At more advanced stages of endometriosis, adhesions can be thicker and denser.

This classification system stages are:

• Stage I (minimal): At this stage, there are only a few superficial endometrial implants.
• Stage II (mild): At this stage, there are a greater number of implants, and the implants are deeper.
• Stage III (moderate): At this stage, there are many deep endometrial implants, cysts on one or both ovaries, and filmy adhesions.
• Stage IV (severe): At this stage, there are many deep endometrial implants, large cysts on one or both ovaries, and adhesions are thicker and denser.

Note that these descriptions of the stages are not absolute, and there is overlap between the stages. For example, endometriosis can be staged at I or II even with filmy adhesions present. Categorization is based on findings during diagnostic surgery, which in most cases will be laparoscopic surgery, which uses a small incision and a long flexible camera.

Staging can be a useful tool for healthcare providers, especially when making treatment decisions and evaluating if a treatment has been effective. However, staging has its drawbacks.

Drawbacks of staging

Staging does not account for the level of pain being caused by endometriosis, because the level of pain does not always correlate with the stage of the disease. For example, a woman with stage I endometriosis may experience severe pain, and a woman with stage III endometriosis may only have minimal pain.

Staging also does not take into account the impact endometriosis has on fertility, which again, does not always correlate with the stage of the disease. For this reason, staging is sometimes complemented by something called the endometriosis fertility index (EFI), which considers other fertility factors such as age and medical history, including prior history of pregnancy and infertility.

This staging system also does not take into account deeply infiltrating endometriosis (DIE), a subtype of endometriosis that has implanted deeper than 5mm into the tissues that line the pelvic cavity, though this is addressed in another complementary classification system called the Enzian proposal.

Individualized approach

While staging can be useful, it is only one way to look at a diagnosis. Endometriosis is different for everyone and requires an individualized approach to treatment. If you have endometriosis or symptoms of endometriosis, it is important to work with a healthcare provider who understands the disorder and can guide you through treatment.