Inguinal Endometriosis in a Nulliparous Woman Mimicking an Inguinal Hernia: A Case Report with Literature Review

A 33-year-old nulliparous woman reported having left groin pain radiating to the left thigh and aggravated by menstruation that lasted for 2 years prior to her presentation. She had regular menstrual cycles and denied any gynecological symptoms suggestive of endometriosis such as dysmenorrhea or dyspareunia. She was otherwise healthy with no previous abdominal or pelvic surgeries or any gynecological interventions. She never received hormonal therapy or contraception and she was not on any regular medications. Upon physical examination, she had a 1.5-cm left inguinal mass, tender on palpation and adherent to the underlying tissue. Ultrasonography of the abdomen and pelvis showed an ill-defined speculated solid hypoechoic left inguinal mass measuring 1.6×1.4 cm in diameter. The uterus and ovaries were within normal limits. Computed tomography (CT) of the pelvis revealed a central hypo-attenuation left inguinal mass measuring 1.7×1.2 cm in diameter and thickening of the left round ligament ( Figure 1 ). There were no other identified lesions, or suspicion for endometriosis, malignancy, or inguinal lymphadenopathy. Based on the presentation, examination, and imaging, left inguinal hernia was one of our differential diagnoses. The patient underwent left inguinal canal exploration that revealed a 1.5-cm mass adherent to the round ligament and floor of the canal. The mass was excised completely with a 0.5-cm safety margin. The inguinal canal floor was repaired and strengthened with proline mesh. The patient tolerated the procedure well and was discharged in good condition. The mass was sent for histopathological examination. Macroscopically, the excised mass was 3.5×3×1.5 cm in size, and consisted of fibrous tissue, with a cut section showing hemorrhagic areas. Histopathological examination showed multiple foci of endometrial glands surrounded by endome-trial stroma embedded within the fibrous tissue ( Figure 2 ). Postoperatively, the patient was followed up in surgery and gynecology out-patient clinics. She had no recurrences. There was no need for further imaging or postoperative hormonal therapy according to the consultant gynecologist.

Endometriosis is a common gynecological disorder, with an estimated incidence of 10% in women of reproductive age [ 1 ]. It typically involves intra-pelvic organs and peritoneum, but can also affect any extra-pelvic organs [ 2 ]. It commonly occurs after implantation of endometrial tissue during previous pelvic surgical procedures [ 3 ]. Inguinal endometriosis is a rare clinical entity that was first reported in 1896 by Cullen. Its incidence is not estimated, as there are only around 50 cases reported in the literature. It represents a diagnostic dilemma as it is often misdiagnosed as other inguinal pathologies such as inguinal hernia, soft tissue tumors, and inguinal lymphadenopathy [ 3 – 5 ]. Most of the reported cases are managed surgically without preoperative imaging or biopsy [ 6 ]. Herein, we report a case of left inguinal endometriosis in a virgin nulliparous middle-age woman with no previous gynecological procedures, mimicking an inguinal hernia.

Endometriosis is characterized by the presence of normal endometrial tissue including glands and stroma at sites other than the uterine cavity. The ovaries are the most commonly affected organ, accounting for 96% of cases. Extra-pelvic endometriosis is much less commonly seen but can involve any organ [ 2 ]. Patients with inguinal endometriosis are often multiparous women with a history of previous gynecological or obstetric surgery [ 7 , 8 ]. We performed an extensive review of the English literature using the search terms “inguinal endometriosis”, “groin endometriosis” and/or “extra-pelvic endometriosis” in the title, abstract, and/or keywords of articles indexed in the Medline, Scopus, and Google Scholar databases, which is summarized in Table 1 . Only 29 cases of inguinal endometriosis have been reported in nulliparous women similar to our case [ 3 – 49 ]. Patients usually present with a palpable inguinal swelling that is often associated with cyclic pain and change in size. Cyclic exacerbation of symptoms is a typical feature for endometriosis that is often missed during the initial assessment [ 9 , 10 ]. A history of dysmenorrhea, dyspareunia, and infertility may also be present, indicating concomitant pelvic endometriosis [ 10 – 14 ]. However, most patients, including this case, have regular menstrual cycles, which can be a misleading point in the clinical assessment [ 8 , 9 ]. Inguinal endometriosis is more common on the right side. This is believed to be associated with the presence of the sigmoid, which places pressure on the left inguinal area, acting as a preventive measure [ 8 ]. Our patient had left-sided inguinal endometriosis, which is less common, as only 13 cases in the literature review were reported on the left side [ 3 – 49 ]. Inguinal endometriosis mimics a wide variety of inguinal conditions such as inguinal hernia, hemangioma, lymphadenopathy, and hydrocele of canal of Nuck [ 3 – 5 ]. The preoperative diagnosis of inguinal endometriosis is difficult owing to its rarity and inconclusive imaging findings. In the literature, there is no comparative study assessing the efficacy of different imaging modalities in such cases. On ultrasonography, inguinal endometriosis 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 [ 5 , 11 , 16 , 50 ]. CT may not be helpful in confirming the diagnosis of inguinal endometriosis, but it can be used to exclude other possible differentials diagnoses [ 14 , 17 ]. However, it did not confirm the diagnosis of -inguinal endometriosis in this case. Magnetic resonance imaging (MRI) is the most specific and sensitive imaging modality for the diagnosis of endometriosis in general. MRI can detect iron particles in the hemosiderin present in the endometrioma, making it a better tool for diagnosing endometriosis than the other modalities [ 10 , 16 ]. The typical appearance of inguinal endometriosis is similar to pelvic endometriosis on MRI, showing high intensity on T1-weighted images and hypointensity on T2-weighted images [ 17 , 51 ]. However, the majority of reported cases in the literature have reported inconclusive MRI results for diagnosing inguinal endometriosis. The MRI findings were commonly atypical and non-specific for endometriosis; therefore, the diagnosis of inguinal endometriosis cannot be established [ 11 ]. A case series involving 20 patients diagnosed with inguinal endometriosis showed that the majority of patients have a mixed hyper- and hypointensity of both T1- and T2-weighted images (61.1% and 50%, respectively) [ 18 ]. Preoperative fine-needle aspiration cytology (FNAC) is diagnostic for endometriosis [ 19 , 20 ]. However, it is rarely performed, as most patients are treated surgically with a preoperative diagnosis of incarcerated inguinal hernia or other inguinal pathologies. The final diagnosis is confirmed by histopathological examination of the excised mass showing endometrial glands and stroma [ 8 , 19 ]. In our patient, CT findings did not suggest endometriosis, and an inguinal hernia was still one of the differential diagnoses. Therefore, preoperative FNAC was not done, as it could have injured the contents of the hernial sac. It is common for patients with inguinal endometriosis to have co-existing inguinal hernia or hydrocele of canal of Nuck. The management of both conditions is surgical [ 5 , 21 , 22 , 52 ]. The surgical management for inguinal endometriosis requires radical excision to decrease the rate of recurrence [ 52 ]. However, most patients are managed surgically before being diagnosed with endometriosis; therefore, the radical surgical resection is not done in most cases without evidence of recurrence on follow-up [ 3 , 12 , 23 ]. Patients with inguinal endometriosis often have concomitant pelvic endometriosis. It is recommended to refer patients for complete gynecological assessment postoperatively [ 16 , 21 , 22 ]. Laparoscopic evaluation of pelvic endometriosis in patients with inguinal endometriosis is recommended if there is clinical evidence of pelvic endometriosis such as dysmenorrhea, dyspareunia, or infertility [ 10 , 11 , 19 , 21 ]. The use of hormonal therapy for inguinal endometriosis is controversial. Its role is more prominent in patients with concomitant pelvic endometriosis. It is sometimes recommended in patients with inguinal endometriosis as an adjuvant therapy after surgical intervention to decrease the risk of reoccurrence [ 7 , 18 , 19 , 21 ]. In our case, the patient did not have any clinical evidence of pelvic endometriosis, so she was only given follow-ups with gynecology without the need for diagnostic laparoscopy and hormonal therapy.

Inguinal endometriosis is a rare clinical entity mimicking other common inguinal conditions. A high index of suspicion is crucial for its preoperative diagnosis, especially in the presence of an inguinal mass associated with cyclic changes in size and pain severity. FNAC is diagnostic but rarely performed. FNAC for a patient in whom there is a high suspicion of inguinal hernia can injure the contents of the hernia sac. Its standard management is surgical excision. Gynecological assessment is needed pre- and postoperatively to exclude the presence of pelvic endometriosis.