Endometriosis affects around 1 in 10 girls and women of reproductive age worldwide, according to the World Health Organization (WHO), and it’s a common cause of chronic pelvic pain and infertility. Endometriosis can affect the ovaries, fallopian tubes, bowel, bladder, or other organs. Bowel endometriosis is endometriosis that involves the intestines.

Endometrial tissue makes up the endometrium — the lining of the uterus. It evolves and sheds throughout the menstrual cycle. In someone with endometriosis, lesions (also called implants or nodules) of endometrial-like tissue grow and shed outside of the uterus, producing symptoms like pain and inflammation wherever they may be present.

What Is Bowel Endometriosis?

Endometriosis of the bowels occurs in 5 percent to 12 percent of women diagnosed with endometriosis, according to the International Journal of Women’s Health. Bowel endometriosis most commonly involves the sigmoid colon and rectum, found at the end of the large intestine.

One form of bowel endometriosis is called superficial, meaning it’s limited to the outer surface of the intestines. Another form is deep (or deeply) infiltrating endometriosis — a severe type of endometriosis that infiltrates, or invades, organs in the pelvis and abdomen.

Bowel endometriosis can also involve the wall between the rectum and the vagina, called the rectovaginal septum.

Symptoms of Bowel Endometriosis

The symptoms of bowel endometriosis overlap with those of endometriosis that affects other organs. Bowel endometriosis also shares many symptoms with irritable bowel syndrome (IBS).

Endometriosis symptoms tend to worsen immediately before and during menstruation, but may be constant. Common symptoms include:

• Chronic pelvic or abdominal pain
• Painful menstrual periods
• Heavy menstrual periods
• Pain during sexual intercourse
• Nausea, vomiting, and bloating
• Infertility or difficulty getting pregnant
• Fatigue
• Depression and anxiety
• Urinary tract symptoms, including difficulty urinating

Bowel symptoms of endometriosis include:

• Painful bowel movements
• Blood in the stool during menstruation, a rare symptom
• Constipation or diarrhea
• Severe pain

How Does a Doctor Diagnose Bowel Endometriosis?

In diagnosing bowel endometriosis, your health care provider will take a medical history, perform a physical examination, run laboratory and imaging tests, and perform a laparoscopy procedure if determined necessary.

History and Physical Examination

A medical history includes gathering information about your symptoms, history of diseases or surgeries, and family history of disease. A physical exam, including a pelvic exam, can identify where pain is occurring and help localize possible sites of lesions. A pelvic exam may even reveal the presence of nodules in the pelvis, frequently seen with deep infiltrating endometriosis lesions affecting the bladder and rectum.

Laboratory Tests

Blood tests for endometriosis include standard tests, such as a complete blood count, and may also include tests for biomarkers of endometriosis, such as CA-125 (cancer antigen 125). Additionally, tissue biopsies taken during a laparoscopy require histologic testing — laboratory testing used to identify exactly what type of tissue any lesions are made of.

Imaging

Imaging techniques used to diagnose bowel endometriosis include ultrasound and MRI. A CT scan may also be used. A transvaginal ultrasound is used to find the location of lesions and determine the extent of invasion into tissue.

MRI is also used to identify lesions and is more sensitive than CT for seeing detail in soft tissue like the bowels. A barium enema may also be used to image the bowels using X-rays or fluoroscopy. Imaging is important to help determine what surgical interventions may be needed.

Imaging techniques can be effective in finding nodules that are larger than 1 centimeter in size — but less effective in detecting superficial endometriosis.

Laparoscopy

Laparoscopy, a minimally invasive surgery, is used to both diagnose and treat endometriosis. During this procedure, a surgeon makes a small incision below the belly button and inserts a small video camera, called a laparoscope. This camera can help the surgeon view the inside of a person’s abdomen and pelvis. Endometriosis lesions can be identified, biopsied, removed, or destroyed during laparoscopic surgery. Laparoscopy can also sometimes miss bowel nodules that are smaller than 1 centimeter.

What Causes Bowel Endometriosis?

The exact cause of endometriosis is not known, but researchers believe genetic and environmental risk factors play a role. Several theories exist about how endometriosis forms. Among them is retrograde menstruation — when menstrual blood flows backwards into the pelvis. Another theory is, it can form if cells end up in abnormal locations during embryonic development in the womb.

Inflammation and immune system responses to endometrial-like tissue play a role in the development of endometriosis. The risk of endometriosis also has a genetic component. It is not directly inherited, but tends to run in families.

What Are the Treatments for Bowel Endometriosis?

Treatments for endometriosis aim to reduce or eliminate pain and other symptoms by removing lesions or limiting the response of lesions to the sex hormone estrogen. Both medical management and surgery are used to treat endometriosis.

Medication

Medical management for endometriosis aims to reduce the size and activity of lesions and control the pain they cause. Nonsteroidal anti-inflammatory drugs (NSAIDs) are used to treat pain and to reduce inflammation. NSAIDs include over-the-counter drugs, such as ibuprofen (Motrin) and naproxen (Aleve), as well as prescription drugs, such as diclofenac (Cataflam).

Hormonal therapy is used to treat endometriosis by controlling levels of estrogen and other hormones. Endometriosis lesions respond to increased estrogen levels during the menstrual cycle, and this process contributes to painful symptoms. Hormonal contraceptives — including oral, injected, and implanted birth control — help combat increases in estrogen and associated symptoms. Combined (estrogen plus progestin) or progestin-only birth control can also be effective.

Other drugs that are used to decrease estrogen levels include gonadotropin-releasing hormone (GnRH) analogues, like elagolix (Orilissa). Hormonal therapy can often provide adequate control of symptoms, even in severe forms of endometriosis, but surgery is frequently needed.

Surgery

Surgery is used to diagnose endometriosis as well as to treat it by removing lesions and adhesions (scar tissue that forms between organs). Depending on the extent of disease and exactly which organs are involved, surgery may be more involved.

Laparoscopic surgery is typically used for treating endometriosis, but laparotomy, or open surgery, is sometimes required. Bowel endometriosis lesions that are superficial or limited to a very small area can sometimes be removed by shaving off a portion of the bowel surface or removing a small circle of bowel wall, a procedure called a disc resection.

Lesions that involve larger areas of the bowels or that are causing complications, like bowel obstruction or stenosis (narrowing), typically require removing a short length of the intestines (segmental bowel resection). When a portion of bowel is removed, the remaining bowel must be reattached, forming what is called an anastomosis.

In some cases the bowel cannot be immediately reconnected. Instead, the bowel is temporarily sewn to a hole in the abdominal wall, creating a stoma. A stoma, such as a colostomy, can allow time for the bowel to rest and heal before being rejoined.

What’s the Outlook for Someone With Bowel Endometriosis?

Bowel endometriosis can be very painful and difficult to treat, but the overall outlook is very positive. Medication alone can help control symptoms, but surgery is often needed. Even after surgery, hormonal treatment is often required to fully treat symptoms.

After surgery, bowel endometriosis can recur, especially with less aggressive surgery. Repeated surgeries are sometimes needed to provide relief. A diagnosis of bowel endometriosis can be scary given the potential complications and likely need for surgery, but, like other forms of endometriosis, it is very treatable.

Talk With Others Who Understand

MyEndometriosisTeam is the social network for people with endometriosis and their loved ones. On MyEndometriosisTeam, more than 126,000 members come together to ask questions, give advice, and share their stories with others who understand life with endometriosis.

Are you living with bowel endometriosis? How do you manage your symptoms? Share your experience in the comments below, or start a conversation by posting on your Activities page.