Endometriosis is a painful condition in which tissue that normally lines your uterus (endometrial tissue) grows in other parts of your pelvis, such as your ovaries or fallopian tubes.

The different types of endometriosis are based on where the tissue is located. In bowel endometriosis, endometrial tissue grows on the surface or inside of your intestines.

Up to one-third of women with endometriosis have endometrial tissue on their bowel. Most bowel endometriosis occurs in the lower part of the intestine, just above the rectum. It can also build up in your appendix or small intestine.

Bowel endometriosis is sometimes part of rectovaginal endometriosis, which affects the vagina and rectum.

Most women with bowel endometriosis also have it in more common sites around their pelvis.

This includes the:

  • ovaries
  • pouch of Douglas (the area between your cervix and rectum)
  • bladder

Some women don’t experience any symptoms. You might not realize you have bowel endometriosis until you get an imaging test for another condition.

When symptoms do occur, they may be similar to those of irritable bowel syndrome (IBS). The difference is, endometriosis symptoms often start around the time of your period. This tissue is responding to the hormonal cycle of your period, swelling and affecting the tissue around it.

Symptoms unique to this condition include:

  • pain when you have a bowel movement
  • abdominal cramps
  • diarrhea
  • constipation
  • bloating
  • straining with bowel movements
  • rectal bleeding

Most women with bowel endometriosis also have it in their pelvis, which can cause:

  • pain before and during periods
  • pain during sex
  • heavy bleeding during or in between periods
  • fatigue
  • nausea
  • diarrhea

Doctors don’t know exactly what causes bowel endometriosis or other forms of the disease.

The most widely accepted theory is retrograde menstruation. During menstrual periods, blood flows backward through the fallopian tubes and into the pelvis instead of out of the body. Those cells then implant in the intestine.

Other possible causes include:

  • Early cell transformation. Cells left over from the embryo develop into endometrial tissue.
  • Transplantation. Endometrial cells travel through the lymph system or blood to other organs.
  • Genes. Endometriosis sometimes runs in families.

Endometriosis affects women during their reproductive years.

Your doctor will start by doing a physical exam. During the exam, your doctor will check your vagina and rectum for any growths.

These tests can help your doctor diagnose bowel endometriosis:

  • Ultrasound. This test uses high-frequency sound waves to create pictures from inside your body. A device called a transducer is placed inside your vagina (transvaginal ultrasound) or your rectum (transrectal endoscopic ultrasound). An ultrasound can show your doctor the size of the endometriosis and where it’s located.
  • MRI. This test uses powerful magnets and radio waves to look for endometriosis in your bowel and other parts of your pelvis.
  • Barium enema. This test uses X-rays to take pictures of your large intestine — your colon and rectum. Your colon is first filled with a contrast dye to help your doctor view it more easily.
  • Colonoscopy. This test uses a flexible scope to view the inside of your intestines. Colonoscopy doesn’t diagnose bowel endometriosis. However, it can rule out colon cancer, which can cause some of the same symptoms.
  • Laparoscopy. During this surgery, your doctor will insert a thin, lighted scope into small incisions in your belly to find endometriosis in your abdomen and pelvis. They might remove a piece of tissue to examine. You are sedated during this process.

Endometriosis is divided into stages based on the amount of tissue you have and how deeply it extends into your organs:

  • Stage 1. Minimal. There are small patches of endometriosis on or around organs in your pelvis.
  • Stage 2. Mild. The patches are more extensive than in stage 1, but they aren’t inside your pelvic organs.
  • Stage 3. Moderate. Endometriosis is more widespread, and it’s starting to get inside organs in your pelvis.
  • Stage 4. Severe. Endometriosis has penetrated many organs in your pelvis.

Bowel endometriosis is usually stage 4.

Endometriosis can’t be cured, but medicine and surgery can help manage your symptoms. Which treatment you get depends on how severe your endometriosis is and where it’s located. If you don’t have symptoms, treatment may not be necessary.

Surgery

Surgery is the main treatment for bowel endometriosis. Removing the endometrial tissue can relieve pain and improve your quality of life.

A few types of surgery remove bowel endometriosis. Surgeons can perform these procedures through one large incision (laparotomy) or many small incisions (laparoscopy). Which type of surgery you have depends on how large the areas of endometriosis are, and where they’re located.

Segmental bowel resection. This is done for larger areas of endometriosis. Your surgeon will remove the part of the intestine where endometriosis has grown. The two pieces that remain are then reconnected with a procedure called reanastomosis.

More than half of women who have this procedure are able to get pregnant afterward. Endometriosis is less likely to come back after resection than with other procedures.

Rectal shaving. Your surgeon will use a sharp instrument to remove the endometriosis on top of the bowel, without taking out any of the intestines. This procedure can be done for smaller areas of endometriosis. Endometriosis is more likely to come back after this surgery than after segmental resection.

Disc resection. For smaller areas of endometriosis, your surgeon will cut out the disc of affected tissue in the intestine and then close the hole.

Your surgeon can also remove endometriosis from other parts of your pelvis during the operation.

Medication

Hormone therapy won’t stop endometriosis from progressing. However, it can relieve pain and other symptoms.

Hormonal treatments for bowel endometriosis include:

  • birth control, including pills, patch, or ring
  • progestin injections (Depo-Provera)
  • gonadotropin-releasing hormone (GnRH) agonists, such as triptorelin (Trelstar)

Your doctor may recommend over-the-counter or prescription nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil) or naproxen (Aleve), to help relieve pain.

Endometriosis in the bowel can affect your fertility — especially if you also have it in your ovaries and other pelvic organs. Up to half of women with this condition are unable to conceive. Surgery to remove the endometriosis lesions can improve your odds of getting pregnant. Even if fertility isn’t an issue, some women have chronic pelvic pain associated with this condition, which has an impact on their quality of living.

Endometriosis is a chronic condition. You’ll likely have to manage its symptoms throughout your life.

Your outlook will depend on how severe your endometriosis is and how it’s treated. Hormonal treatments and surgery can help manage your pain. Symptoms should improve once you go through menopause.

Endometriosis can have a big impact on your quality of life. To find support in your area, visit the Endometriosis Foundation of America or the Endometriosis Association.