Endometriosis tissue forms the lining of the uterus. When tissue similar to this grows in the bowel, it causes bowel endometriosis.

Bowel endometriosis involves the abnormal growth of endometrial-like tissue in the intestines.

In this article, learn more about the symptoms of bowel endometriosis, how doctors diagnose it, and what treatments are available.

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Endometriosis tissue typically grows in the uterus to prepare the body for ovulation and possibly fertilization.

Bowel endometriosis occurs when endometrial-like tissue grows on the bowel or intestines.

Blood cells, connective and gland tissue make up endometriosis tissue. It thickens every month until it sheds during menstruation if fertilization does not occur.

When tissue similar to this grows outside the uterus, such as on the bowel, it still thickens in response to hormones. However, because this endometrial-like cannot leave the body, it causes a variety of symptoms.

Doctors usually classify endometriosis as either superficial or deep. In superficial endometrial-like tissue grows on the surface of the bowel. If the tissue penetrates the bowel wall, it is called deep bowel endometriosis.

According to a 2018 review, after the genital organs, the bowel is the most common location for abnormal endometrial-like tissue to grow.

10–12% of American females between 15–44 years old have endometriosis. It is especially common among people in their 30s and 40s. Of those, 5–12% have bowel involvement.

Symptoms of bowel endometriosis may include:

Abnormal endometrial-like tissue can grow on any part of the bowel. However, according to 2020 research, about 90% of the incidences of bowel endometriosis involve the rectum or sigmoid colon.

These symptoms may mimic other bowel conditions, including irritable bowel syndrome (IBS), according to 2022 research. The addition of menstrual-related symptoms should help distinguish between those conditions and bowel endometriosis.

Symptoms of bowel endometriosis may vary between individuals and depend on a person’s menstrual cycle. For example, symptoms may be worse in the days leading up to or during menstrual bleeding.

Symptoms of bowel endometriosis may decrease once a person enters menopause and estrogen levels decrease.

Doctors do not know exactly why some people develop endometriosis.

It is possible that past surgery involving the uterus may allow endometrial cells to attach to the incision and eventually transfer to the bowel.

Some researchers think an imbalance of estrogen may also contribute to endometriosis.

There also appears to be a genetic link. People who have a close family member, such as a mother or sister, with the condition are at an increased risk of developing endometriosis.

Researchers still do not know why endometrial-like tissue grows outside the reproductive organs, such as on the bowel.

Surgery is the only certain way to diagnose all forms of endometriosis.

Because symptoms of bowel endometriosis can mimic other intestinal problems, it is essential to rule out conditions, such as colitis, rectal tumors, and IBS.

After a physical exam including a pelvic examination, a review of symptoms, and medical history, a doctor may order additional tests, including:

A colonoscopy may not help with diagnosis. If lesions remain on the outside of the bowels, this imaging procedure will not see the tissue growth. Doctors may prefer a sigmoidoscopy for initial testing, as it is less invasive.

There is currently no cure for endometriosis, but many treatments are available.

Treatment for bowel endometriosis may depend on how severe a person’s symptoms are, their overall health, and whether they want to become pregnant.

Treatment may include the following:

Pain medication

If a person’s symptoms are mild, a doctor may recommend managing them with over-the-counter or prescription pain medication. These drugs include acetaminophen and ibuprofen.

The medication will not stop the abnormal tissue growth but may reduce pain and discomfort.

Hormone therapy

Since estrogen plays a role in bowel endometriosis, hormone therapy may help manage the condition.

Hormonal treatment may involve taking birth control patches or pills. These medications contain estrogen, progesterone, or both, and help prevent the buildup of endometrial-like tissue. They may also shrink the growth on the bowel.

In other cases, a doctor may prescribe gonadotropin-releasing hormone, which prevents ovulation and the growth of the endometrial-like tissue.

The symptoms might return if a person stops taking the hormones.

Surgery

A doctor may also recommend surgery if hormone therapy does not ease symptoms or if a person wishes to become pregnant. Depending on the depth of the tissue growth, a surgeon may cut out the tissue or remove a section of the intestine completely.

Excision surgery involves cutting or shaving the endometrial-like tissue on the bowel but leaving the intestines intact. If the growth is deep, a surgeon will remove the lesions and close any holes in the bowel.

In severe cases, a surgeon may remove a portion of the intestine that has endometrial-like tissue before reattaching the remaining sections of the bowels. The medical term for this is segmental resection.

According to a 2016 report, complications of surgery include leaking bowels, torn bowels, a fistula, or bowel obstruction.

There is no conclusive evidence that a specific diet can ease symptoms of bowel endometriosis.

Some studies suggest that eating fruits and vegetables links to fewer endometriosis symptoms.

For example, a 2018 study looked at 70,835 premenopausal women. The results indicated that those who ate one or more servings of citrus fruits daily had a 22% lower risk of developing endometriosis than those who ate fewer citrus fruits. However, the study did not look at bowel endometriosis specifically.

A 2021 review suggests that people who take fish oil supplements along with vitamin B12 supplements may experience fewer endometriosis symptoms. The same report says alcohol and red meat consumption may make symptoms worse.

Another small study looked at females who had IBS, endometriosis, and bowel symptoms that worsened during menstruation.

The study indicated that eating a low FODMAP diet might ease bowel symptoms possibly associated with endometriosis.

Learn more about diet changes for endometriosis here.

The outlook for people with bowel endometriosis depends on the severity of their symptoms and the effectiveness of treatment.

Although endometriosis is a chronic condition, there are treatments, such as hormone therapy and surgery, which can help to reduce symptoms.

In many cases, symptoms of bowel endometriosis ease when estrogen levels decline after menopause.