Recently, a study hit my inbox about Endometriosis mimicking an inguinal hernia. So, of course, my interest was piqued and research had to take place! Be warned, though, it’s considered VERY rare. In all the literature I’ve read, only 42 cases have been referenced as being documented inguinal Endo. But when has rarity stopped me from sharing something about Endometriosis? Yeah. Never. Here we go!

What is AN inguinal hernia?

An inguinal hernia is the most common type of hernia (about 70% of hernias are inguinal) and usually manifests as a small lump in the groin area. Both men and women can get inguinal hernias, but it’s apparently more common in men. It occurs if there’s a small hole in your abdominal cavity which allows fat or intestines to seep through, which can a lump or swelling to occur.

What are THE symptoms?

There may be a lump beneath the skin near the groin. Sometimes, the lumps are uncomfortable, but sometimes they cause no pain. And sometimes the lumps disappear when you lay down – the lump can recede back into the abdominal cavity! Sneezing, coughing, or straining may aggravate the hernia.

To make matters even worse: Sometimes there IS NO LUMP; it may just feel weird in the groin area when you walk or stand.

Even if a weird, lower abdominal/groin lump is discovered but isn’t painful, please still go to your doctor for an examination, diagnosis, and treatment. Most often, a hernia can be diagnosed with an easy visit to your physician. Sometimes, imaging studies may be needed, but not often. Doing nothing may lead to further complications or the need for emergency surgery!

What if your doctor HAS found an inguinal hernia? Surgery may be performed to move the intestines/fat/whatever-is-poking-out back to its original position AND close up the tear.

Now…what’s this Endometriosis masquerading as an inguinal hernia business? Let’s find out:

What are the Symptoms of Inguinal Endometriosis?

After reading all of the studies summarized below, here’s what I learned from others’ experiences with inguinal endometriosis:

• There is usually a lump in the groin area (it could be the left or the right groin)
• The lump may or may not hurt
• The lump may or may not hurt more during your period
• The lump may or may not disappear when you lay down
• The lump may or may not grow in size during your period
• The lump did cause leg numbness in one woman

Frustrated? Me, too. Have a lump? Go do you doctor!

How is inguinal Endometriosis diagnosed?

Usually by accident! Actually, in the studies I’ve summarized below: most of the cases of inguinal endometriosis were diagnosed was by accident. A patient went in for surgery to repair an inguinal hernia and found inguinal Endometriosis instead! In a few cases, though, the doctors actually suspected inguinal Endometriosis.

How is Inquinal Endometriosis Treated?

Excision of the mass seems to be the treatment I’ve seen in these studies below. And for most of the women in these studies, their groin pain resolved after the Endometriosis mass was removed, with no recurrence. And, for most, there was no need to go on hormonal treatments after excision.

My thoughts

Again, I cannot stress how rare inguinal Endometriosis is. But I also cannot stress enough: if you have any of these symptoms, never be ashamed to go to your doctor and press for answers! Never, ever, ever. Be your own advocate. And if you need to back your claims up with science, I’ve summarized many studies below and linked to them so you can print them out, too.

SCIENCE!

Following is a list of studies I’ve found about inguinal hernias which turned out to be Endometriosis. Several studies reference that the first case inguinal endometriosis was discovered in 1896! But don’t take my word for it: read on!

During the Prohibition Age, in December of 1921 to be exact, a study was published in the Annals of Surgery of Mrs. E.B., who was 50 years old and and had pain and tenderness in the right inguinal region. She had begun to have pain in that area over 15 years earlier. It varied in intensity over the years. During her periods, the pain worsened and the size of the mass increased. After five successful pregnancies and three miscarriages, a doctor told her a hysterectomy would fix her ongoing pain. She underwent the procedure in 1918, but the pain continued and worsened around the time she would have been menstruating. Fast forward to 1921: The mass also caused her pain there when she coughed so her doctor told her she had an inguinal hernia. Surgery was performed and an inguinal hernia was, indeed, discovered…as was a mass found within the inguinal canal, connected to the rectus sheath. The mass and the attached portion of the rectus sheath were removed and the hernia was repaired. Biopsy showed the mass “contained a thick chocolate-like fluid.” Her diagnosis: “chronic inflammation; transplantation of the endometrium.” Back in the day that meant Endometriosis. And my favorite quote from the study? “…she [Mrs. E.B.] was delighted that her pain was gone.” Wouldn’t you be, too?

In 1945, the Glasgow Medical Journal reported two cases of discovered inguinal Endometriosis:

1. A 38-year-old housewife developed a swelling along the right side of her groin that was painful. The swelling and pain worsened “when she knocked it against objects in the course of her housework.” The lump hurt more while she was on her period and was about the size of a walnut. It was excised during surgery and was found to be gray with “small, red, fleshy areas” when it was sliced into. Biopsy confirmed Endometriosis and she was symptom-free during an examination two years later.
2. Another housewife, this one 46-years-old, complained of a swelling in her right groin that occurred after an injury eight years prior (she received “a blow” to the lower abdomen). At that time, her physician fitted her with a sort of hernia belt and diagnosed her with a hernia. Six years of wearing that device seemed to keep the swelling at bay. She stopped wearing it and during the subsequent two years realized the swelling and pain recurred, increasing around her period. The lump was surgically removed and it seemed it had “multiple small brown cysts” and was associated with endometrial tissue. Over a year later she was still pain-free.

Three cases of groin Endometriosis was reported in the March 1949 edition of the British Medical Journal:

1. Around 1939, a woman noticed a small lump appear in her right groin the day before her period. It was painful and swelled up to nearly the size of an egg and walking made the pain worse. On the last day of her period, it shrank down to the size of a pea. Each subsequent period started with the day before having that painful lump reappear (although it never again was as large as an egg) and it would once more shrink and become less painful as her period ended. In 1941, she complained of the painful lump to her doctors. They could feel the lump in the right groin area and excised it and confirmed the mass to be Endometriosis. She was symptom-free for 18 months, but in July of 1943, the same mass reappeared around her period and was painful. It was directly beneath the scar of her previous incision. Surgery was considered, but they opted to watch and wait. Two months later, her paid had receded and the lump eventually faded. At a 1948 follow-up, she had no recurrent symptoms.
2. In 1946, a woman was leaning up against a table and became aware of a painful lump in her right groin area. Over a period of two years, it increased in size and pain. It used to only be painful if it was pushed upon, but as time passed it was painful even with no added pressure. A few days before her periods, it would suddenly hurt for no reason (it would worsen more if she was walking uphill or stretched her right leg outward), and that ache would cease once her period started. In 1948, her doctors examined her and found the lump to be near where a femoral hernia would develop. However, they suspected either Endometriosis or a form of Adenomyosis. It was excised and confirmed to be Endometriosis. Three months later, there was no recurrent symptoms.
3. A 37-year-old woman complained of a three-year history of a cherry-sized lump in her right groin. The last year of that history, the lump had become extremely hard and painful to touch. Sometimes the pain and swelling would increase, and sometimes she had a “prickling” sense near the lump. It didn’t hurt during her periods, but always became painful if it was touched or pushed on during sex. During surgery, they discovered the mass fused to the round ligament in the external inguinal ring. The mass and a portion of the round ligament, were removed and biopsied: the mass oozed dark blood when cut into and was determined to be an Endometrioma. A month later, she had no recurrent symptoms.

In 1958, the American Journal of Obstetrics & Gynecology published an article about two women. Unfortunately, I only have access to the first study: a 34-year-old woman, Mrs. S., complained of a lump in the right groin area for five years. Every month, one day before her period began, the lump would appear. During her period, it would grow to about the size of a walnut and completely disappear within five days of her period ending. It was tender and was “more or less painful.” At the time of their examination, the doctors could not feel the lump. Based on her symptoms, the physicians suspected Endometriosis and performed surgery anyway. A small mass was found connected to her round ligament within a hernial sac. The hernia was repaired, the lump excised, and pathology confirmed it was Endometriosis.

A study published in the Annals of Surgery in 1960 discussed four separate cases of inguinal Endometriosis that occurred at the same hospital:

1. A 49-year-old woman, the wife of a physician I might add, had a firm, tender inguinal mass for two weeks. She was admitted to the hospital for what they suspected was a hernia. The lump protruded when she stood or coughed, and it magically disappeared when she laid down and didn’t change during her period. Sixteen years prior, she had a cyst removed from her inguinal region (back then they also thought her mass was a hernia). This woman had two prior normal pregnancies and no abnormal menstrual history. Surgery was performed: no hernia was found, just a series of cysts along her round ligament. Pathology confirmed it was Endometriosis and she had no recurrent symptoms at her post-op.
2. A 34-year-old woman was admitted to the hospital in 1954 for a suspected inguinal hernia. The mass was hard and tender to the touch. Her complaints weren’t related to her period, she never had any children, and she only had a surgery nine years prior for vaginal stenosis. The lump was found and removed from along the round ligament of her deep inguinal ring. Pathology confirmed the mass was Endometriosis. Nine months later, the patient returned to her physician with complaints of pelvic pain, her physician suspected it was Endometriosis, but the patient never followed-up for further care.
3. In 1946, a 49-year-old woman was admitted to the hospital after she had a mass for eight years in her inguinal area. It had slowly grown over time and was not tender or acted any differently during her period. Surgery was performed and they found a cyst of the round ligament located within the inguinal canal and external ring. The cyst “contained old blood.” Pathology confirmed cystic Endometriosis and she had no recurrent symptoms at follow-up.
4. A 36-year-old woman who had never had children was admitted to the hospital in 1958. Over the past year, she had a small mass that had grown on the right side of her lower abdomen. During her period, the mass grew slightly larger and created a pinching/cutting pain that would end when her period ended. Pelvic and rectal exams were normal, but her physician did feel the 2-3cm lump when she stood up. In surgery, they found the 3cm mass sticking out of the round ligament, as well as an inguinal hernia which was found separate from the mass. The mass was excised, the hernia was repaired, and pathology confirmed the lump was Endometriosis. She was diagnosed with Endometriosis of the round ligament. Several months later, she was still symptom-free.

In 1977, The American Surgeon published an article of a woman with extraperitoneal endometriosis and states that an Endometriosis diagnosis must be considered if “the groin mass is associated with menstrual variability in size and in tenderness.”

An August 1991 study by Obstetrics and Gynecology followed six women who presented to surgery for inguinal hernias. Each of them ended up having Endometriosis lesions in the extraperitoneal portion of their round ligament (six of seven lesions were discovered on the right side) and each of the women also had Endometriosis discovered within the intraperitoneal areas, too.

In 1999, the Turkish Journal of Medical Sciences published an article about two women who had inguinal Endometriosis:

1. A 30-year-old woman complained of a lump in her right groin for a year and a half. The lump had grown over time and was painful during her periods. It was less painful, but still hurt, even when she wasn’t on her period. Before surgery, her doctors suspected Endometriosis. After surgery, they confirmed it! No hernia was found. Neither were chocolate cysts. But the mass was located adjacent to the round ligament, was fibrous, and contained Endometriosis tissue scattered throughout it. There was no Endometriosis found within the pelvic cavity. And she was symptom-free 13 months after her surgery.
2. Similarly, a 29-year-old woman also had a lump on the right side of her groin. She had it for three years, it had grown in size, and was also painful near and on her periods. The ultrasound didn’t show anything useful and a gynecological exam was normal. She underwent surgery and no hernia or chocolate cysts were found. They did find the mass, though, and it was brownish-gray in color. They cut it out and pathology confirmed it was Endometriosis. She, too, was symptom-free, even 17 months after the surgery.

The Canadian Journal of Surgery published two separate cases of inguinal Endometriosis in 1999:

1. A 42-year-old woman had right groin pain for one month near an area of swelling that varied in size. Her pain worsened when she stood for long periods of time, although her physicians could find nothing wrong. Three months later, at a follow-up exam, she still had pain in the area but the examination was again normal. And an ultrasound revealed nothing out of the ordinary. Another three months passed and she returned with ongoing pain. This time her physician was able to feel a small mass in her right groin and she was diagnosed with an inguinal hernia. In surgery, they found a 1cm blueish colored mass attached to her round ligament. Biopsy concluded it was an Endometrioma. They also discovered bilateral chocolate cysts. A year after the excision, she had no recurrent symptoms.
2. After three months of swelling and intermittent groin pain, a 27-year-old woman went to her physician. A physical examination revealed a lump within her right groin near the inguinal ring. They suspected an inguinal hernia and performed surgery to repair it. Pathology confirmed it was an endometrioma and was fine a year after surgery.

Now this one is a little bit different. In the February 2001 edition of Southern Medical Journal, a 24-year-old woman developed a right inguinal hernia after heavy lifting. She had the hernia surgically repaired with no problems. The incision that was made shared a previous c-section scar incision. Four months later, she returned to her doctor with pain in that right area again. Two months after that appointment, a “deep painful bulge appeared” and surgery was performed because a recurrent hernia was suspected. Nope: it revealed an Endometrioma. The authors suspect transplantation of tissue from the c-section scar may have caused the Endometrioma to develop.

A study published in May of 2001 was of a 40-year-old woman who developed a lump on the groin that was tender to touch. The pain and swelling oftentimes worsened during her period and sometimes she had numbness in her leg on the same side as the lump. Wide-excision of the mass was completed and it was confirmed as Endometriosis. Prior to surgery, they suspected it was an inguinal hernia or perhaps a displaced ovary.

A 2005 study published in the Archives of Gynecology and Obstetrics showed three women who had suspected inguinal hernias were actually diagnosed as inguinal Endometriosis after exploratory surgery and excision. The lesions were once more all discovered on the round ligament.

The Singapore Medical Journal published a 2007 study of a 37-year-old woman who had a lump on her right groin area for the past two months. It didn’t hurt during her period. Exams showed the lump was present and an ultrasound revealed an inguinal hernia. In surgery, they discovered a 4cm x 4cm mass attached to her round ligament. It was removed (along with a portion of the round ligament, inguinal canal, and abdominal wall) and pathology confirmed it was Endometriosis. There was no hernia or other Endometriosis found. During her post-op, she had no further groin pain. Interestingly enough, this study states that Endometriosis has “been reported to affect all organs except the heart and spleen.”

A 2007 study published in Australasian Radiology stressed the the importance of using MRIs in such a situation. At 20-years-old, a gal had surgery to remove a cyst, adhesions, and Endometriosis. Eight years later, she noticed a tender lump near her groin area that stuck around for seven months. Its size fluctuated depending on if she was on her period or not. An MRI confirmed the presence of the mass on her right side, as well as a cyst on her left ovary. She underwent surgery to remove the cyst and the mass. The lump was found attached to her round ligament and confirmed as Endometriosis. The study suggests she had multiple MRIs because it was instrumental in capturing the changing size of the mass prior to surgery during her period, as well as having her physicians conclude it was likely Endometriosis prior to her surgery.

The Journal of Cytology published a 2008 study of a 37-year-old woman who had swelling of the right groin area a few months after having a c-section. The swelling caused her pain and a “stretching sensation” that varied and increased in intensity. A surgeon excised the mass, but no pathology was done. She was pain-free for a few months, but then it returned five and a half years later; the swelling came back in the same spot. The lump was again discovered on the round ligament, was excised, and this time was sent to pathology. A laparoscopy was also done and no evidence of Endometriosis was found within her pelvic region. A biopsy confirmed the mass was Endometriosis.

As we previously read, MRIs may prove to be a valuable tool in diagnosing inguinal Endometriosis. In 2009, the Japanese Journal of Radiology wrote about a 31-year-old woman who had “intense pain” in her groin area while on her period. A hard mass was felt during physical examination and located via MRI at the round ligament. After the lump was surgically excised, she was pain-free.

Cases Journal published a 2009 study of a 29-year-old woman who had two days of unexplained and sudden pain and swelling near her right groin and her pain increased when she was lying down. She had been on birth control, had previously been diagnosed with IBS, and was lactose intolerant. Her doctors felt the lump and suspected a femoral hernia or an enlarged lymph node. However, during surgery a “hard inflammatory mass” was found on the round ligament; no hernia or enlarged lymph node could be seen. The mass was cut out and sent to pathology for analysis and was determined the mass was Endometriosis.

Also in 2009, the Upsala Journal of Medical Sciences published a study of a 40-year-old woman who had a tender mass near her right groin for two years. When she was 23, she was diagnosed with Endometriosis. After her diagnosis, she was on four months of hormonal drugs and “had complete pain relief.” When she was 28, she delivered a child and noticed a small, painless lump near her groin during her pregnancy. A year later, she was had her second child and again noticed that same painless lump during her pregnancy. When she was 36 years old, that soft “pregnancy lump” became hard and remained painless. When she was 38, the lump became painful. The size of the mass and intensity of pain didn’t change when she was on her period. It was just there. And it hurt. Her surgeon, dermatologist, and gynecologist all told her it was fine. At 40, she sought out a fourth opinion because of her “severe groin pain.” They could feel the lump beneath her skin and confirmed its presence with CT and MRI scans. Like so many of these lumps, it was found on the round ligament and was adhered to the inguinal canal. They removed the mass and (surprise!) it turned out to be Endometriosis. She remained pain-free after the surgery.

ISRN Obstetrics & Gynecology published a 2011 study of a 48-year-old mother of three who complained of an inguinal mass on her right groin and uterine bleeding for two months. Usually her periods were pain-free, but over the past two months they were painful near her groin. Upon physical examination, the lump was non-tender and the the ultrasound was normal except for a “bulky uterus.” Fine Needle Aspiration was used to biopsy a sample of the mass, which pathology confirmed was Endometriosis. She underwent a surgery to remove the 5cm x 6cm mass from her inguinal canal, as well as a D&C to help de-bulk her “bulky uterus” (I think I just like typing that). Pathology once more confirmed the lump was Endometriosis. The 48-year-old woman remained symptom-free since excision.

BMJ Journals published a 2013 study of a 49-year-old woman who had swelling of her left groin for about six months. She also had a dull, aching pain near the swollen area. If she lifted heavy weights, the swelling increased, but there was no increase in swelling or pain when she was on her period. After an exam, they suspected an inguinal hernia and surgery was performed. The cyst (as they called it) was located on the left round ligament and extended to the vaginal wall. Biopsy confirmed it was Endometriosis. No recurrent pain at her follow-up appointments.

Endometriosis: it’s not just for women! A study published in 2014 in the Avicenna Journal of Medicine of a 52-year-old man who went to the E.R. with complaints of “excruciating stabbing pain in the right lower abdomen and pelvis area for 3 weeks.  The pain was worse on getting up from a supine position and was not relieved by bowel movements. It slightly increased upon urination as well.”  Seven months before, he had undergone inguinal hernia repair (which had been surgically repaired a few times before) and had a medical history of cirrhosis due to Hepatitis C.  He underwent a diagnostic laparoscopy and a mass was discovered attached to his bladder and his hernia site.  It was filled with blood, was removed, and biopsied.  It was Endometriosis, complete with it’s own estrogen and progesterone receptors.  After his surgery, his pain completely resolved.

Another study published in 2014 was in BMJ Journals and was of a 25-year-old woman who complained of right-sided hip pain, which was aggravated with hip flexion and adduction. A lump had been present near her right hip for a year and remained unchanged for six months. An MRI showed a small mass near her round ligament, which led her doctors suspected a few things, including an abscess or an inguinal hernia. Surgery was performed, the lump was excised, and was found to be Endometriosis.

A study titled, Jack in the Box: Inguinal Endometriosis, published in a 2015 edition of BMJ Journals was of a 39-year-old woman who had left-sided swelling who was diagnosed with an inguinal hernia. During the prior six months, it had increased pain and swelling around her period. She didn’t have painful periods, cramps, or painful sex. An examination revealed swelling that extended from her inguinal region to her labia majora. Due to the fact that it had no other symptoms of a hernia, her physician suspected inguinal Endometriosis and performed surgery. Endometriosis was found along the round ligament all of the way along the ligament to her labia majora. It was excised, confirmed to be Endometriosis, and the patient had no recurrent symptoms a year later.

Another 2015 study published in BMJ Journals was of a 32-year-old woman who’s primary doctor suspected an inguinal hernia and referred her to a general surgeon. For two years, she had painful swelling near her right groin, which had gradually worsened especially during her periods. She had no documented history of Endometriosis, but had a c-section seven years prior. The lump could be felt on her right groin near her c-section scar. The general surgeon suspected an inguinal hernia with the possibility of “an endometrial deposit.” An MRI ruled out a hernia, but still supported the suspicion of an Endometrioma. The mass was excised, confirmed to be an Endometrioma, no hernia was discovered, and she was doing well 15 months after surgery.

In August 2019, an abstract was published in BMJ Journals of a 41-year-old woman who was clinically diagnosed with an inguinal hernia, but the mass was later surgically diagnosed as Endometriosis. She had complained of groin swelling over the past month since her last period and had an unremarkable surgery and gynecological history.

(Published on October 29, 2019)

Resources:

American Journal of Obstetrics & Gynecology (Article, Feb. 1958) – Inguinal Endometriosis

Annals of Surgery (Study, Dec. 1927) – Inguinal Endometriosis

Annals of Surgery (Study, June 1960) – Inguinal Endometriosis

Archives of Gynecology and Obstetrics (Abstract, Jan. 2005) – Inguinal endometriosis

Australasian Radiology (Abstract, Jan. 2007) – Inguinal Endometriosis Attaching to the Round Ligament

Avicenna Journal of Medicine : Article (2014) An Unusual Cause of Abdominal Pain in a Male Patient : Endometriosis

BMJ Journals (Study, 2013) – Endometriosis of Extra-Pelvic Round Ligament, a Diagnostic Dilemma for Physicians

BMJ Journals (Study, May 2014) – An Unusual Presentation of Endometriosis

BMJ Journals (Study, 2015) – Jack in the Box: Inguinal Hernia

BMJ Journals (Study, 2015) – A Case of Endometriosis Presenting as an Inguinal Hernia

BMJ Journals (Abstract, Aug. 2019) – Inguinal Endometriosis: a Differential Diagnosis of Right Groin Swelling in Women of Reproductive Age

British Medical Journal (Study, March 1949) – Endometriosis of the Groin

Canadian Journal of Surgery (Article, Oct. 1999) – Endometrioma Simulating Inguinal Hernia: Case Reports

Cases Journal (Study, Aug. 2009) – Endometriosis Presenting as an Acute Groin Swelling: A Case Report

Europe PMC (Abstract, May 2001) – Extraperitoneal Inguinal Endometriosis

Glasgow Medical Journal (Study, March 1945) – Endometriosis of the Inguinal Region: Report of Two Cases

ISRN Obstetrics & Gynecology (Study, 2011) – Inguinal Endometriosis: An Uncommon Differential Diagnosis as in Inguinal Tumor

Japanese Journal of Radiology (Abstract, Feb. 2009) – Magnetic Resonance Imaging Findings of Extrapelvic Endometriosis of the Round Ligament

Journal of Cytology (Study, 2008) – Inguinal Endometriosis: A Case Report

Obstetrics and Gynecology (Abstract, Aug. 1991) – Inguinal Endometriosis: Pathogenetic and clinical implications.

Singapore Medical Journal (Study, 2007) – Endometriosis of the Inguinal Canal Mimicking a Hernia

Southern Medical Journal (Abstract, Feb. 2001) – Scar Endometriosis Manifested as a Recurrent Inguinal Hernia

The American Surgeon (Abstract, June 1977) – Extraperitoneal inguinal endometriosis

The British Hernia Centre – Inguinal Hernia

Turkish Journal of Medical Sciences (Study, July 1999) – Inguinal Endometriosis: A Report of Two Cases and a Review of Literature

Upsala Journal of Medical Sciences (Study, July 2009) – A Case of Inguinal Endometriosis with Difficulty in Preoperative Diagnosis

~ 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