Appendiceal endometriosis refers to the medical condition affecting a small percentage of women where endometrial-like tissue grows in and around the appendix.

The incidence rates of appendiceal endometriosis are highly variable. Different studies have reported rates between 1 and 22 percent of women with endometriosis having some form of appendiceal involvement.

Causes of appendiceal endometriosis

Endometrial tissue is the tissue that normally lines the uterus and undergoes shedding and bleeding every month in response to hormonal changes during the menstrual cycle. In nearly 10 to 20 percent of all women of reproductive age, endometrial tissue is found in other locations, including the appendix. While the endometrial tissue in the appendix responds to hormonal changes during the menstrual cycle by breaking down and bleeding just like the normal endometrial tissue, it cannot exit the body. This results in local inflammation, pelvic pain, and other symptoms associated with endometriosis.

Symptoms of appendiceal endometriosis

Appendiceal endometriosis may be asymptomatic (without any signs or symptoms) or may be associated with complications such as acute appendicitis, acute lower gastrointestinal hemorrhage (bleeding), intestinal perforations, or intussusceptions (blockage of the gastrointestinal tract).

 The symptoms of appendiceal endometriosis are very similar to those of acute appendicitis. They include sudden pain in the lower abdomen that becomes worse upon movement, loss of appetite, nausea and vomiting, abdominal bloating, constipation or diarrhea, and fever. However, these symptoms overlap with the menstrual cycle in the case of appendiceal endometriosis.

Diagnosis of appendiceal endometriosis

The diagnosis of appendiceal endometriosis can be complex but early diagnosis is key because, if left untreated, appendiceal endometriosis can lead to complications such as bleeding or perforation in the intestines and obstruction of the bowels.

Physical examination, colonoscopy, and imaging tools such as CT scans may all be used to diagnose appendiceal endometriosis. However, the most definitive diagnostic method is laparoscopic surgery, which allows histopathological evaluation of the appendix.

Management and treatment of appendiceal endometriosis

The most common method of managing appendiceal endometriosis is surgical removal of the appendix (appendectomy).

Non-surgical CO2 laser treatment can vaporize superficial spots of endometriosis that are present on the surface of the appendix.

In complicated cases, surgical treatment may require ileocecectomy (the removal of a portion of the ileum, a part of the small intestine), and right hemicolectomy (removal of a portion of the colon or the large intestine) in addition to appendectomy to restore bowel continuity and function.

Clinical trials

An interventional clinical trial (NCT01921634) is recruiting an estimated 100 participants at the Penn State Milton S. Hershey Medical Center in Pennsylvania to assess whether the incidence of appendiceal endometriosis is related to the method of pathologic analysis and to resolve the high variation in the number of cases reported by different studies.

Women ages 18–51 whose appendix was removed at the time of laparoscopy for the treatment of endometriosis and/or pelvic pain are eligible to take part in the trial. Women who had a previous appendectomy are ineligible.

Tissue specimens from consenting patients will be collected and analyzed according to the American College of Obstetrics and Gynecology (ACOG) recommendations. The primary outcome measure will be the incidence of appendiceal endometriosis. The study is expected to be completed in June 2020.

Last updated: Aug. 6, 2019


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