Extrapelvic endometriosis happens when endometrial tissue grows in places other than the reproductive organs, including the bowel, bladder, and lungs. This condition is likely underdiagnosed.

Extrapelvic endometriosis is when endometriotic tissue grows outside your pelvic cavity, in places such as your bowels, urinary tract, and chest.

Endometriosis may cause severe pain, especially during your period. Endometriosis typically affects the organs near your uterus, such as your ovaries and fallopian tubes. But it can also occur farther away.

Extrapelvic endometriosis occurs when endometrial tissue grows in more distant areas of the body, where it’s not supposed to grow. Endometriosis typically only affects the organs inside your pelvis, such as the ovaries and fallopian tubes.

The hormonal changes during your menstrual cycle affect this tissue, making it grow, thicken, and eventually break down. This causes inflammation, discomfort, and pain. For people with extrapelvic endometriosis, this pain can occur wherever endometriosis grows.

Doctors separate extrapelvic endometriosis into types based on which organs and areas of your body are affected. Let’s go over the most common types of this condition.

Intestinal endometriosis

Also called bowel endometriosis, this type causes endometrial tissue to grow on your bowels (intestines). Intestinal endometriosis is the most common type of extrapelvic endometriosis.

Intestinal endometriosis can cause the following symptoms, which often worsen around your period:

Urinary tract endometriosis

Urinary tract endometriosis (UTE) is the second most common type of extrapelvic endometriosis. It affects parts of your urinary system, such as your:

Bladder endometriosis is the most common type of UTE.

Up to 50% of people with UTE don’t have any symptoms. Others may experience the following symptoms, which might get worse around menstruation:

Thoracic endometriosis

Thoracic endometriosis affects your chest cavity, including the lungs. It’s a rare and difficult to diagnose type of endometriosis.

Symptoms of thoracic endometriosis include the following, which may worsen before or during your period:

Other types of endometriosis

Other, less frequent types of extrapelvic endometriosis include:

  • skin endometriosis
  • endometriosis of the nervous system

Endometriosis can also develop in other parts of your body, but it’s extremely rare.

Researchers don’t know exactly what causes endometriosis or extrapelvic endometriosis, but there are a few theories.

One theory about what causes endometriosis is that it happens because of a process called retrograde menstruation. During this process, menstrual blood flows backward through your fallopian tubes and into your pelvic cavity. The endometrial cells in that blood may invade nearby tissue and start growing.

This theory, which is frequently challenged, falls short in a few ways. First, retrograde menstruation is common in people without endometriosis, so it doesn’t explain why some people develop endometriosis, and some don’t.

Second, it doesn’t entirely explain extrapelvic endometriosis. Retrograde menstruation wouldn’t typically cause endometrial cells to travel to places like the chest or abdominal wall. One theory is that these cells travel through abnormalities in the diaphragm.

According to another theory, endometrial tissue might travel from your uterus to other parts of your body through your bloodstream or lymphatic system.

Yet another theory suggests that endometriosis begins in cells that already exist outside of your pelvic area. Under certain circumstances, they can transform into endometrial cells, causing extrapelvic endometriosis.

The cause of endometriosis is still an active area of research.

Extrapelvic endometriosis is difficult to diagnose because the symptoms are often attributed to other, more common conditions.

Also, people with symptoms of extrapelvic endometriosis typically consult general practitioners rather than gynecologists who have more experience with endometriosis. A 2020 research analysis discovered that 84% of extrapelvic endometriosis cases are treated by non-gynecological medical practitioners.

Your doctor might suspect extrapelvic endometriosis if you experience recurring pain, discomfort, or other symptoms outside of your pelvic area during menstruation.

They will then review your medical history and perform a thorough physical exam. Your doctor will also likely recommend imaging tests of the affected area.

Endometriosis is typically confirmed during a minimally invasive procedure called a laparoscopy. This allows doctors to see directly into the pelvic and abdominal cavity and take samples of tissue to examine under a microscope.

Treatment of extrapelvic endometriosis depends on the affected area and the severity of your symptoms.

Many people with extrapelvic endometriosis take hormone medications, like birth control pills, to help regulate their menstrual cycle. These can help prevent the monthly thickening of endometrial tissue that happens before your period.

Your doctor might also recommend taking over-the-counter or prescription pain medication around the time of menstruation.

Some people may need surgery to remove endometrial tissue from the affected area. Surgery can help reduce pain, but endometriosis may return.

Other therapies may be helpful for some people. These include:

Extrapelvic endometriosis happens when endometrial tissue grows in parts of your body outside the pelvis. It can cause mild to severe pain during periods. Talk with a doctor if you experience pain, digestive issues, or other symptoms that worsen during your period.