Endometriosis & the Appendix

Diagram of the appendix

Here I go again, once more intrigued by Endometriosis growing in odd places inside the body.  Today I’m going to focus on the appendix.  I’ve read that many women have their appendix removed because physicians may confuse Endometriosis pain for the symptoms of appendicitis.  But on Tuesday an article hit my email about Endometriosis growing on the appendix…and I became obsessed.

Please remember: I don’t write this to scare you, or freak you out, or say that all of your right-sided abdominal pain is from Appendix Endo.  Take a deep breath – I like to document these things in case anyone would like to discuss it further with their healthcare providers so they may be aware during surgery.  Appendiceal Endometriosis is considered extremely rare and it is suspected that only 1-3% of all cases of Endometriosis involve the appendix.  But…knowledge is power.

In November of 2018, I underwent my fourth Endometriosis-related surgery and am my very own walking case of appendiceal Endometriosis!

What & Where is the Appendix

The appendix is part of the gastrointestinal tract attached to a section of the large intestine, where it meets the small intestine.  It is located in the lower right section of your abdomen, and is a skinny 4″ long tube.  If you have pain in that location, especially when it’s pushed on, physicians may suspect appendicitis.

Appendix: Necessary Organ or Leftover, Useless Tissue?

Depending on who you ask, the appendix does (or doesn’t) serve a purpose.  Hence why so many people no longer have theirs.  If it’s inflamed, it’s typically removed.

Many believe the appendix to be a “vestigal organ” or an organ that used to have a purpose, but has since evolved into uselessness.   Recently, though, some researchers have theorized that the appendix is not a useless flappy tube, rather it houses good gut bacteria – aiding in recovery from GI issues and illnesses and strengthening the immune system.

Is it useless?  Does it safely store good gut bacteria?  Who really knows…

Endometriosis versus Appendicitis

Symptoms of appendicitis can include fever, abdominal pain, abdominal swelling, loss of appetite, vomiting, an inability to fart (yes, I said “fart”), constipation, or diarrhea.  Many of these symptoms can mirror complaints and symptoms of Endometriosis.  Hence, an often misdiagnosis of appendicitis.

Appendicitis may develop because of inflammation, an infection, or even a blockage to the appendix.  When infected or blocked-up, the bacteria inside the appendix goes nuts, the appendix can fill with puss and swell up.  If left untreated, it can burst or rupture…which simply means it tears.  It shouldn’t pop like a balloon.  If it does rupture,the nastiness-fluid from within can spread all over the pelvic cavity, which may infect other organs or even cause sepsis, which can be fatal.

Is every bit of lower right-abdominal pain associated with appendicitis? No. It could just be something you ate, bad gas, period cramps, anyyyything.  Or it could be appendicitis.  AND some women with Endometriosis of the appendix don’t have any symptoms – it’s just discovered by accident.

But that being said: sometimes Endometriosis can affect the appendix…One study stated that out of 1,500 appendectomy biopsies,  0.80% had Endometriosis.  I’ve read that some surgeons believe that the appendix should be removed during Endometriosis excision surgery as a preventative measure, even if it appears healthy.

If you’re worried, please do your research and talk to your healthcare provider.  As usual, there doesn’t appear to be any type of pre-operative diagnostic tests for the presence of Endo on the appendix. Ya gotta go in and see it for yourself…aka surgery.

Now, for the SCIENCE!

Documented Cases of Endometriosis on the Appendix

And before you bury yourself in reading numerous cases of women with Endometriosis of the appendix, I wanted to share an image with you of what Endometriosis on the appendix can look like.  Dr. Andrew S. Cook of Vital Health took this photograph during an excision surgery and has granted me permission to share it with you today:

Photo of Endometriosis on the appendix, taken by Dr. Andrew Cook of Vital Health Institute
Photo by Dr. Andrew S. Cook, Vital Health Endometriosis Center; used with permission

Endometriosis on the appendix is nothing new – as my research will show.

The earliest published study I found online featuring Endometriosis on the appendix was published in 1929 in the Canadian Association Medical Journal.  It covered three cases of women with Endometriosis:  one with an Endometrioma, the second with Endometriosis on her appendix, and the third with Endometriosis in a surgical scar.  I find it incredibly interesting that they dissect the theories of Endometriosis for each: contributing the first to Sampson’s theory, the second they simply note as “an unusual situation”, and the third they cite the German’s theory of tissue change (metaplasia).  Just a fun little piece of historical literature on our disease. (I sense a new obsession festering…)

In 1960, medical records were reviewed from 30 appendectomies which occurred between 1919-1955 at St. Luke’s Hospital in Chicago, Illinois.  Each was pathologically confirmed as Endometriosis of the appendix.  Of those 30 women, 11 presented with symptoms which mimicked appendicitis.  Four of those 11 presented with pain at the onset of their periods.  It was noted that none of the 30 women had recurrent symptoms after their appendectomies, although many of them were found to have pelvic Endometriosis.  Sixteen of the 30 women also went through partial or full hysterectomies at the time of their appendectomies.

In 1975, researchers combed through medical records of the Kapiolani Hospital in Hawaii and reviewed 12 documented cases of appendiceal Endometriosis, ranging from 1968-1973.  During those years, the Hospital performed 1,496 appendectomies – of those, 12 tested positive for Endometriosis of the appendix.  Additionally, the researchers interviewed the 12 women for further details and information.  Many were found to have Endometriomas during surgery, too.  Seventy-five percent of those women complained of abdominal pain prior to their surgeries.  Which means, some didn’t – they had complaints of lower back pain and period pain.  Unfortunately, the study doesn’t go into detail of how they fared after their surgeries.

A study published in 1981 documents a 23-year-old Nigerian woman who was 35-weeks pregnant and had complaints of vaginal bleeding and right-sided pain.  Appendicitis was suspected, so a surgery was performed and her appendix was inflamed and torn.  Her appendix was removed and the child was safely delivered by c-section.  A biopsy revealed Endometriosis along the appendix wall where the rupture occurred, but nowhere else.

Another study in 1981 reviewed the medical records of 50 patients diagnosed with Endometriosis between 1968-1978 at Mount Carmel Mercy Hospital in Detroit, Michigan. Of those 50, 16 had confirmed Endometriosis of their appendix, the youngest of whom was only 14 years old…and the oldest?  Sixty-two!  Their complaints ranged from abdominal pain, to heavy periods, to GI complaints.  Many had pain located in their lower-right abdominal quadrant.  Pre-operative diagnoses included acute appendicitis, uterine fibroids, and ovarian cysts.  During surgery, two were found to have ruptured appendixes with abnormalities, six had inflamed appendixes, and eight had normal-appearing appendixes.  Seven of the 16 women also had total hysterectomies performed at the time of surgery.  Biopsies on all confirmed Endometriosis.  After surgery, two had recurrences of Endometriosis and it was later discovered in their sigmoid colons.

In 1983, a study reviewed the literature and medical records from 1950-1981 from the Department of Pathology Frederiksberg Hospital in Denmark.  During that time period 10,000 appendices were removed and biopsied.  Of those, 22 tested positive for Endometriosis of the appendix.  Of all of the medical records reviewed during that time period, 800 patients were found to have Endometriosis.

In 2007, a study was published about a 35-year-old Japanese woman who complained of three days straight of abdominal pain (especially on the right side) and nausea.  She had a history of mildly-painful periods, and had finished her last one three weeks prior.  She was admitted into the hospital and imaging studies revealed fluid within her pelvic cavity, as well as inflammation of her pelvic lining.  The physicians suspected either a perforated/ruptured appendix or a ruptured ovarian tumor or dermoid cyst.  Surgery was performed and the appendix was found to stuck to her abdominal wall and was also “markedly enlarged” – so it was removed.  Biopsies confirmed the appendix wall had been infiltrated with Endometriosis and likely caused her appendix to rupture.  She was discharged two weeks later and was doing well.

In 2008, a study was published about two women in Turkey with appendiceal endometriosis.  A 45-year-old woman went to the ER because of severe pain and nausea during the second day of her period.  Lab work and imaging studies revealed nothing out of the ordinary, but she was tender to the touch.  Due to the progressive severity of her pain while at the hospital, a laparotomy was performed and her inflamed appendix was removed.  The interior wall of her appendix was confirmed by biopsy to to have Endometriosis present.  Secondly, a 41-year-old woman went to the ER because of nausea, painful urination, and severe pain on the right side of her abdomen.  Again, testing appeared mostly normal and due to the progression of her pain, surgery was performed.  Her appendix was “covered with a brown-dark red colored material.”  A ruptured endometrioma on her right ovary was suspected as having released the fluids throughout.  Biopsy results yielded Endometriosis.

In Africa, a 2008 study was about a 25-year-old woman checked into the hospital with complaints of right-sided abdominal pain for the past day.  She was also nauseous and vomiting.  Lab results were normal and she was sent home and told to consult with a gynecologist.  Three months later, she again went to the hospital with identical symptoms.  The lab results were normal, but she was admitted for two days, then released.  Four months later, she returned.  This time she had the abdominal pain with diarrhea, but no nausea or vomiting.  Tests showed she had a small cyst, and she was admitted for five days.  Upon release, she was urged to consult with a gynecologist and a psychiatrist (I wish you could sense my anger as I typed that last word…).  Nine months later, she was readmitted to the hospital for the same issues.  This time, they performed an appendectomy and her appendix appeared normal…that is, until biopsy (yes, you guessed it) – it confirmed the presence of Endometriosis on her appendix.

In 2010, a study was published about a 29-year-old Japanese woman who had right lower abdominal pain for two days.  She had similar symptoms about a year prior.  She had a history of painful periods, accompanied by fever, and had been treating with her gynecologist with traditional Chinese medicines.  Imaging studies showed a slight calcification and thickening of her appendix wall and she was diagnosed with acute appendicitis, and sent off for am immediate appendectomy.  It was removed, appeared mildly inflamed, and was sent off for biopsy.  You guessed it:  Endometriosis.  After surgery, she had no residual pain or feverish periods.

A 2011 study was of a 36-year-old Greek woman who complained of abdominal pain, swelling, constipation, and an inability to flatulate (is that a better word than farting? I think not.  I still giggle.) for the past three days.  She had a history of using contraceptive pills and painful periods.  Imaging studies revealed a large blockage in her intestine which they presumed to be a tumor.  She underwent an laparotomy, and they discovered numerous adhesions, an inflamed appendix, and her bowel was incredibly swollen.  They removed the adhesions and her appendix and resected a large portion of her bowel.  Pathology reports confirmed Endometriosis on her colon and her appendix.  She treated with Triptorelin (a GnRH agonist) for her Endometriosis and six months later she had to undergo a second surgery to restore her resected bowel.  No Endometriosis lesions were found and she was doing well.

A South African study published in 2016 study discussed a 33-year-old woman who had been suffering with infertility, even after three IVF attempts.  She complained of pain to the right side of her abdomen for the last four hours, and was nauseous.  She was hot to the touch, and tender at the right side of her stomach.  Her pregnancy test and urine tests were normal, but given her infertility a CT was performed, which revealed a mildly-enlarged appendix, and let her physicians to suspect the onset of appendicitis.  Laparoscopy was performed to remove her appendix, which was was visually inflamed, and while inside they noticed a “reddish brown area” on her uterus, which was excised and biopsied.  Endometriosis was confirmed on her uterus and her appendix biopsy came back negative for appendicitis.  However, her meso-appendix (a flap of connective tissue between the appendix and the ileum) did come back as having Endometriosis on it.

A study published in a Canadian journal in 2016 was about a 34-year-old woman who went to the ER due to right-sided abdominal pain.  For the past several months, the pain had returned during her period, which she also started the day before she was admitted.  All of her tests came back normal (except for a cyst spotted on her ovary), and she was discharged home.  Five days later, she returned due to worsening pain.  Due to the suspicions of appendicitis, surgery was ordered.  Her appendix was not inflamed, but did have what was suspected to be a tumor – so the appendix was removed and sent off for biopsy.  The results came back that Endometriosis was on involved with the appendix and mesoappendix.  After surgery, she did not have any recurrence of pain.

Another 2016 study was of a 65-year-old woman in Turkey who had abdominal pain and nausea for the last 24 hours.  She had pain on the right side of her abdomen and lab tests showed elevated inflammatory markers and enlarged appendix.  An appendectomy was performed and a “brownish mass” was found on her appendix.  A biopsy confirmed it was Endometriosis.  She had no recurrent symptoms 30 months after her surgery.

In June 2017, the IJRCOG published a study from India of a 26-year-old woman with a history of Endometriosis.  A year prior, she was diagnosed with an endometriotic cyst, and given six months of Lupron Depot, followed by a birth control pill, and was pain-free.  Her pain returned chronically in her lower abdomen and she returned to her physician.  She was one injected with Lupron Depot, but a week later her pain was so intense she went to the emergency room.  Testing results raised suspicions of appendicitis.  She underwent a laparoscopy, and she was found to have a dense adhesions, a frozen pelvis, and an inflamed appendix.  Her appendix and adhesions were removed and upon biopsy her appendix was confirmed with Endometriosis. The authors conclude that appendix endometriosis is “very rare” and preoperative diagnosis is next to impossible.

In March of 2018, Obstetrics & Gynecology discussed the case of a woman with a known ectopic pregnancy.  She also had a history of pain in her right abdomen.  While they were inside her pelvis dealing with the ectopic pregnancy, they also performed an appendectomy based on their suspicions of appendicitis.  Well, the biopsy results came back as positive for appendiceal endometriosis.

Another article published in 2018 was about a 42-year-old woman who presented with signs of appendicitis.  A laparoscopic surgery was performed and a biopsy confirmed appendiceal endometriosis.  A week after surgery, she had no recurring symptoms of pain.

An October 29, 2018, study found that a 40-year-old woman who complained of pain in the lower right of her torso ended up having Endometriosis on her appendix.  She had a medical history of PCOS and uterine polyps.  In addition to her right lower torso pain, she had lower back pain.  Her pain had been going on for about two days.  After a CT found a mass on her appendix, she underwent a laparoscopy and partial bowel resection.  Four days later, she was released from the hospital.  A follow-up MRI found that she had two Endometriomas on her right ovary.  Now, what’s infuriating about that?  Now she’ll need to go in for ANOTHER surgery to have those dealt with…*sigh*

On November 3, 2018, a study was published of a 29-year-old woman who started her period a day ago and then went to the Emergency Room because of radiating pain from her belly button down to her lower right quadrant.  She was also nauseous and vomiting.  Testing and palpitations were normal, the CT scan was unremarkable, but an ultrasound suggested she was suffering from appendicitis.  A diagnostic surgery was performed and they found 30 ccs of blood (that’s a little over one ounce) in her pelvis due to a ruptured cyst on her ovary.  Although the appendix seemed “contracted upon itself,” no traces of Endometriosis were visible.  They removed her appendix and sent it off to pathology.  Microscopic lesions of Endometriosis were, however, located on her appendix. Her symptoms stopped once she was recovered from surgery.

On November 26, 2018, I underwent my fourth Endometriosis surgery. Earlier in July, I went in for another excision surgery and it was discovered that I had Endo lesions on my small intestine, too deep to remove without a proper bowel resection. So, in November I went in for said resection. Not only was there endo on my small intestine, but also on my cecum, large intestine, and appendix. If you haven’t already read about it, feel free to explore my fourth Endo surgery!

A January 2019 study was of a 41-year-old woman who went to the ER due to lower right quadrant pain. A CT scan led doctors to suspect she had mucocele of the appendix: a blockage which led to a fluid buildup and secretion. She was given antibiotics, but two months later with ongoing complaints she underwent a surgery. The mucocele fluid had leaked from the appendix and invaded the sigmoid colon. The lesion had adhered her appendix to her terminal ileum as well as her sigmoid colon, so they removed her appendix and resected her sigmoid colon. Biopsy of her appendix found the blockage to have been caused by an Endometrial lesion, which caused the leakage and damage to her sigmoid colon.

A March 2019 study followed a 53-year-old woman who was admitted to the hospital for having lower right abdominal pain for the past three days, abdominal bloating for a week, and nausea, vomiting, and fever. A physical examination showed tenderness in her right lower quadrant. Doctors performed a laparotomy to see what was going on and found “copious pus” in her peritoneal cavity. Her appendix was removed and her peritonieal cavity was, in essence, washed out and scrubbed clean of pus. The appendix appeared normal, but during biopsy it was found to be covered in microscopic Endometriosis. The authors warn that Endometriosis may mimic appendicitis.

In July 2019, a study was published of a 35-year-old woman who complaint of lower right abdomen and hip pain for the past year and her pain was not only present during her period. She had a history of infertility, but that was it. A physical exam and blood work were normal. An ultrasound found a lesion in the right ileac fossa and thickening of the ileao-cecal junction (the valve between the small and large intestine). A CT scan showed a large tube-like growth on her cecum and led physicians to believe she had an acute appendicitis. Imaging studies also found multiple cysts on her ovaries. She underwent a laparoscopic appendectomy. The appendix was removed and sent off to pathology and confirmed as appendix endometriosis. Three months after surgery, she remained symptom-free.

Another July 2019 study was of a 29-year-old virgin who went to the emergency room due to abdominal pain and vomiting. She had suffered with those symptoms for a day, but had the same symptoms six months prior. She had no history of prior surgeries or Endometriosis. A CT scan showed she suffered from a small bowel obstruction. They suspected the blockage was caused by scar tissue (aka a band adhesion). Surgery was performed and the appendix was found adhered to the area where the large and small intestine meet. They also found blood in her pelvic cavity. The appendix was removed and the adhesions were removed. Pathology confirmed she and Endometriosis on her appendix and she was referred to a gynecologist for further treatment.

A November 2019 study focused on a 33-year-old woman who went to the ER with complaints of severe right abdominal pain for three days, nausea, vomiting, and a fever. For the past two weeks, she had passed “loose, watery stool” at least four times a day. The right side of her abdomen was tender during examination. Three years prior, she had a cystectomy due to Endometriosis and had dealt with infertility issues. An ultrasound showed an endometrioma on her right ovary and a small mass on her appendix, possibly appendicitis. Surgically, her right cyst was removed, as was her appendix. Biopsy confirmed the appendix mass was Endometriosis. She complained of pelvic pain six weeks alter, but was referred to her gynecologist for futher care.

There were many, many more studies I did not highlight here.  So many!!!

Again, if you’re worried, talk to you doctor.  Supposedly it’s very incredibly rare to have Endometriosis of the appendix, but it does happen.

(Updated January 28, 2020)


Acta Pathologica Microbiologica Et Immunologica Scandinavica (Abstract, July 1983) – Endometriosis of the Veriform Appendix

African Health Sciences (Article, 2008) – Endometriosis of the Appendix

American Journal of Obstetrics & Gynecology (Abstract, 1975) Endometriosis of the Appendix

American Journal of Obstetrics & Gynecology (Article, 1960) Endometriosis of the Veriform Appendix (abstract can be found here)

American Journal of Surgery (Abstract, Oct. 1981) Endometriosis of the Appendix Presenting as Acute Appendicitis

Archives of Gynecology and Obstetrics (Abstract, 2008) – Appendiceal Endometriosis: Two Case Reports

Archives of Medical Science Civilization Diseases – (Article, March 2018) Appendiceal Endometriosis: an Unusual Cause of Acute Appendicitis

Asian Journal of Case Reports in Medicine and Health – (Abstract, March 2019) Appendiceal Endometriosis: A Case Report

BMJ Case Reports – Abstract, July 2019) Endometriosis of the Appendix Causing Small Bowel Obstruction in a Virgin Abdomen

British Institute of Radiology – (Article, Oct. 2018) – A Rare Case of Right Lower Quadrant Pain

British Journal of Obstetrics and Gynaecology (Abstract, April 1981) – Perforation of the Appendix During Pregnancy: A Rare Complication of Endometriosis

Canadian Medical Association Journal (Article, Sept. 1929) – Three Cases of Endometriosis

Case Reports in Gastroenterology (Article, June 2007) – Endometriosis of the Appendix Resulting in Perforated Appendicitis

Ecronicon Endometriosis of Appendix: A Case Report and Review of Literature

Everyday HealthWhat is the Appendix?

HealthlineWhat Does the Appendix Do?  Things to Know

Hiroshima Journal of Medical Sciences (Article, June 2010) A Case of Endometriosis of the Appendix

International Journal of Reproduction, Contraception, Obstetrics and Gynecology – (Article, June 2017) – Concurrent Ruptured Endometrioma with Appendiceal Endometriosis: A Case Report

International Journal of Colorectal Disease – (Abstract, Jan. 2019) – Appendiceal Endometriosis Invading the Sigmoid Colon: A Rare Entity (you may access the full article here)

International Journal of Surgery Case Reports – (Article, Nov. 2018) – Endometriosis of the Appendix Presenting as Acute Appendicitis with Unusual Appearance

International Journal of Surgery Case Reports – (Article, July 2019) – Appendicular Endometriosis: A Case Report and Review of Literature

Journal of Emergency Medicine Case Reports (Article, 2016) – Two Cases of Acute Abdominal Intestinal Endometriosis

Journal of Medical Case Reports (July 2011) Rectal Endometriosis Causing Colonic Obstruction and Concurrent Endometriosis of the Appendix: A Case Report

Journal of Obstetrics and Gynecology Canada (Abstract, Oct. 2016) Isolated Appendiceal Endometriosis

Mental Floss (Article, undated) Immunology Study Suggests the Appendix has a Use After All

Obstetrics & Gynecology (Abstract, March, 2018) Appendiceal Endometriosis and Ectopic Pregnancy Occurring Simultaneously

Science Alert (Article, Jan. 2017) Your Appendix Might Serve an Important Biological Function After All

Science Daily (Article, Jan. 2017) Appendix May Have Important Function, New Research Suggests

South African Journal of Obstetrics and Gynecology (Article, Sept. 2016) – Endometriosis of the Meso-Appendix Mimicking Appendicitis: A Case Report

~ Again, I am a layman.  I do not hold any college degrees, nor mastery of knowledge.  Please take what I say with a grain of salt.  If curious, do your own research Validate my writings.  Or challenge them.  And ALWAYS feel free to consult with your physician. Always.  Yours ~ Lisa