Case Study: Endometriosis or Hernia?

"Medical Journeys" is a set of clinical resources reviewed by doctors, meant for physicians and other healthcare professionals as well as the patients they serve. Each episode of this 12-part journey through a disease state contains both a physician guide and a downloadable/printable patient resource. "Medical Journeys" chart a path each step of the way for physicians and patients and provide continual resources and support, as the caregiver team navigates the course of a disease.

This month: A noteworthy case study.

A 33-year-old woman presented with pain in her left groin that radiated to her left thigh and worsened during menstruation. She told clinicians she had been experiencing these symptoms for the last 2 years, but was otherwise in good health. She noted that her periods were regular, with no severe menstrual cramps or pain, and neither did she have dyspareunia or any other symptoms that might be associated with endometriosis.

She had not undergone any abdominal or pelvic surgeries or gynecological interventions and was not on hormone therapy or contraceptives or any regular medications.

Physical Examination/Scanning

Physical examination identified a 1.5-cm left inguinal mass, which was adherent to the underlying tissue and tender on palpation. Clinicians performed an ultrasound of the abdomen and pelvis, which revealed a poorly defined speculated solid hypoechoic left inguinal mass, 1.6×1.4 cm in diameter. Ultrasound findings of the uterus and ovaries were unremarkable.

Computed tomography (CT) of her pelvis showed a central hypo-attenuation left inguinal mass 1.7×1.2 cm in diameter, and thickening of the left round ligament.

The scan did not reveal any other lesions, or signs of endometriosis, cancer, or inguinal lymphadenopathy. Given the patient's presenting symptoms, and findings of the physical and radiological examinations, clinicians considered left inguinal hernia as one of the differential diagnoses.

Surgical Findings

The patient underwent surgical examination of the left inguinal canal exploration, which revealed a mass measuring 1.5 cm attached to the round ligament and floor of the canal, which was completely excised along with a 0.5 cm margin. Surgeons repaired the floor of the inguinal canal and reinforced it with proline mesh. The patient had no complications from the procedure, recovered well, and was discharged in good condition.

The mass -- which macroscopically measured 3.5×3×1.5 cm and consisted of fibrous tissue with a cut section showing hemorrhagic areas -- was sent to histopathology for assessment, which revealed multiple foci of endometrial glands surrounded by endometrial stroma embedded within the fibrous tissue.

Post-Discharge

After her discharge, the patient attended surgery and gynecology outpatient clinics for follow-up. The consulting gynecologist reported that there was no need for additional surveillance imaging or postoperative hormonal therapy. Her symptoms did not reappear.

Rare and Mimics Other Common Conditions

Clinicians reporting this case of inguinal endometriosis note that because it is a rare clinical entity that mimics several other common inguinal conditions, a high index of suspicion is important for diagnosis before surgical treatment. This is especially crucial in cases involving a palpable inguinal mass, usually associated with cyclic changes in size and severity of pain.

Endometriosis, which affects an estimated 10% of women of reproductive age, typically manifests in intra-pelvic organs and peritoneum, although organs external to the pelvis may also be involved. The condition generally develops following pelvic surgical procedures, due to implantation of endometrial tissue, the authors added.

Inguinal endometriosis, however, is very rare, with only about 50 cases reported in the literature, the case authors noted. As such, "it is often misdiagnosed as other inguinal pathologies such as inguinal hernia, soft tissue tumors, and inguinal lymphadenopathy." Those cases have generally been addressed through surgery, and without the use of diagnostic imaging or biopsy.

First described in 1986, inguinal endometriosis is "characterized by the presence of endometrial stroma and glands in the extraperitoneal portion of the round ligament and in the surrounding connective and lymphatic tissues," explained the authors of a 2021 study of three such cases.

The condition tends to occur in women who have had several children and have undergone gynecological or obstetric surgery, the case authors said, noting that their review of the English literature identified just 29 cases of inguinal endometriosis affecting nulliparous women, as in this patient's case.

Affected women present with an inguinal swelling that is easily detected on palpation, along with cyclical pain and change in size. The authors cautioned that this periodic worsening of symptoms is a typical feature of endometriosis that is often missed during the initial assessment. Patients may also report having pain with menstruation and with intercourse, as well as a history of difficulty conceiving – symptoms suggestive of pelvic endometriosis.

Distinguishing Features

Features that may help distinguish inguinal from pelvic endometriosis include the presence of regular menstrual cycles, which the authors explained, "can be a misleading point in the clinical assessment."

In addition, the right side is more likely to be affected in patients with inguinal endometriosis, presumably due to the presence of the sigmoid colon, which the case authors explained, "places pressure on the left inguinal area, acting as a preventive measure." Only 13 cases of left-sided inguinal endometriosis have been reported in the literature to date, the group said.

The condition can present with symptoms common to various other inguinal conditions, such as inguinal hernia, hemangioma, lymphadenopathy, and hydrocele of canal of Nuck. The rarity, along with inconclusive results of imaging, make inguinal endometriosis very challenging to diagnose before surgery is performed, and the relative efficacy of the various imaging modalities in these cases has yet to be studied, the case authors noted.

Ultrasound imaging often shows "a hypoechoic unilocular or multilocular cyst that is difficult to distinguish from other inguinal region pathologies such as lymph nodes and simple cysts," although it may help rule out possible differential diagnoses, the group stated.

Role of CT

As was the case with this patient, CT does not always help confirm the diagnosis of inguinal endometriosis, but it can be used to exclude other possibilities, the authors noted. "Magnetic resonance imaging (MRI) is the most specific and sensitive imaging modality for the diagnosis of endometriosis in general," due to its ability to detect iron particles in the hemosiderin that is present in the endometrioma. On MRI, both inguinal and pelvic endometriosis show high intensity on T1-weighted images and hypointensity on T2-weighted images, and the generally atypical and non-specific MRI findings for endometriosis prevent a conclusive diagnosis of inguinal endometriosis.

The team referenced a case series of 20 inguinal endometriosis patients in which most had a mixed hyper- and hypointensity of both T1- and T2-weighted images (61.1% and 50%, respectively).

Although preoperative fine-needle aspiration cytology (FNAC) can be used to diagnose endometriosis, it is only rarely utilized because "most patients are treated surgically with a preoperative diagnosis of incarcerated inguinal hernia or other inguinal pathologies," and post-excision, histopathological evidence of endometrial glands and stroma from testing of the mass confirms the diagnosis, the authors said.

They noted that CT findings in their patient did not point to endometriosis, and because a possible inguinal hernia had not been ruled out, they did not use preoperative FNAC, which carried a risk of injuring the hernial sac.

Inguinal endometriosis – typically managed with radical surgery to reduce the chance of recurrence -- often exists concurrently with an inguinal hernia or hydrocele of canal of Nuck -- both of which may be treated surgically before endometriosis is diagnosed. This is why radical surgical resection is not done in most cases without evidence of recurrence on follow-up, the authors explained.

Recommendations

They advised that because inguinal endometriosis often occurs concomitantly with pelvic endometriosis, patients should be referred following surgery for a complete gynecological assessment. Patients with inguinal endometriosis who have clinical symptoms such as dysmenorrhea, dyspareunia, or infertility that suggest pelvic endometriosis should be assessed laparoscopically, the clinicians added.

Hormone therapy may be used in patients with concomitant inguinal and pelvic endometriosis, the authors stated, adding that its use in women with only inguinal endometriosis is more controversial, although it may be recommended as adjuvant postsurgical therapy to reduce the risk of recurrence.

Since their patient had no signs suggesting pelvic endometriosis, she received only gynecological follow-ups, without the need for diagnostic laparoscopy and hormonal therapy, the authors said.

Read previous installments of this series:

Part 1: Endometriosis: Understanding the Pathogenesis and Pathophysiology

Part 2: Diagnosing Endometriosis

Part 3: Managing Endometriosis: Research and Recommendations