Endometriosis of extra-pelvic round ligament, a diagnostic dilemma for physicians

Abstract

A 49-year-old multiparous woman presented with a swelling in the left groin of 6 months duration. The swelling was associated with a dull aching pain. The patient reported increase in size of the swelling during lifting of heavy weights. Menstrual history was normal and there was no increase in pain over the swelling during menstruation. She underwent a caesarean section 20 years ago and the scar had healed by primary intention. She was provisionally diagnosed to have a left-sided inguinal hernia. Ultrasonography showed a multiloculated cyst measuring 5.3×1.5×5.2 cm within the inguinal canal. The patient had excision of the cyst under spinal anaesthesia. Intraoperatively the cyst was found to arise from the left round ligament. It measured 7×6 cm extending to the left lateral vaginal wall. Histopathology revealed endometriosis of the round ligament. Her gynaecological assessment was normal and they recommended no further treatment. On follow-up the patient was asymptomatic and wound had healed well.

Background

Extra-pelvic round ligament endometriosis is a rare entity; painless and left sided is even rarer. It is a disease of specific interest to the physician as it has the propensity to occur in extra-pelvic localisations like skin, viscera and groin. It can be confused with the common affections of the inguinal region and thereby pose a diagnostic dilemma. We recommend considering endometriosis in the differential diagnosis of groin swellings in elderly perimenopausal women too.

Case presentation

A 49-year-old multiparous woman presented with a swelling in the left groin of 6 months duration. The swelling was associated with a dull aching pain. The patient reported increase in size of the swelling during lifting of heavy weights. Menstrual history was normal and there was no increase in pain over the swelling during menstruation. She had undergone caesarean section 20 years ago and the scar had healed by primary intention. She was provisionally diagnosed to have a left-sided inguinal hernia. An ultrasonography was advised. The patient had excision of the cyst under spinal anaesthesia. Intraoperatively the cyst was found to arise from the left round ligament. It measured 7×6 cm extending to the left lateral vaginal wall (figure 1). Histopathology revealed endometriosis of the round ligament (figure 2).

Figure 1.

Intraoperative photograph showing the cyst arising from the round ligament.

Figure 2.

Histopathology showing islands of endometrial glands and stroma (arrow).

Investigations

Ultrasonography showed a multi-loculated cyst measuring 5.3×1.5×5.2 cm within the inguinal canal.

Differential diagnosis

• Lipoma

• Neurofibroma

• Desmoid tumour

• Primary lymphoma

Treatment

The patient underwent excision of the cyst (figure 3). The gynaecological assessment was normal. Transvaginal sonography showed absent left ovary; endometrium was normal. They recommended no further treatment with antiestrogen. She was advised yearly follow-up.

Figure 3.

Excised specimen measuring approximately 7×6 cm.

Outcome and follow-up

Her recovery was uneventful and she was discharged the next day. On follow-up the patient was asymptomatic and wound had healed well.

Discussion

Endometriosis in the inguinal region is rare. The usual presentation is that of a woman in the reproductive age group around 22–46 years with a peak incidence at 30–40 years.¹ It accounts for 0.3–0.6% of patients affected by endometriosis.² Till date, about 70 cases have been reported in literature.³ The groin swelling is usually slow growing, painful with exacerbations during menses. In our case the patient did not have any pain.

The incidence of inguinal endometriosis on the right side is 90–94% as compared to the left.³ There are various proposed theories explaining this. One of them suggested the presence of atypical lymphatics from the peritoneal cavity and pelvis to the right groin.¹ Foster et al⁴ described the clockwise intraperitoneal fluid circulation. Also the endometrial cells remain for a longer time in the right side due to gravity and the left round ligament is protected by the sigmoid colon. Our patient had history of caesarean section and no other pelvic or groin surgeries. She presented with left-sided endometriosis. The only explanation may be the non-obliteration of the parietal peritoneum accompanying the round ligament in the canal of Nuck and through it the retrograde efflux of the endometrial tissue and implantation happens. Inguinal endometriosis may be associated with pelvic or intraperitoneal endometriosis, though rare.⁵

Endometriosis of the round ligament is associated with groin hernias in about 40% of the cases, mostly inguinal.⁶ It is most of the time clinically diagnosed to be a groin hernia and causes a diagnostic dilemma to the physicians. Diagnosis is usually made on histopathology after excision of the cyst. Malignant degeneration though rare is possible.⁷ A colour Doppler is the imaging of choice, with features of a nodular hypoechoic lesion with absence of vascular flow around the lesion.⁸ A CT and MRI are also able to detect the inguinal endometriosis, but reserved to rule out malignancy. En-bloc resection of the lesion along with the extra-pelvic round ligament is the treatment of choice.⁹ Those cases where a preoperative diagnosis of round ligament endometriosis is made, intraperitoneal localisations have to be ruled out by doing a diagnostic laparoscopy. A gynaecological assessment is mandatory and a gonadotropin releasing hormone injection is recommended.¹⁰

Learning points.

• Endometriosis in the inguinal region is rare and accounts for 0.3–0.6% of patients affected by endometriosis.

• The usual presentation is that of a woman in reproductive age group around 22–46 years with a peak incidence at 30–40 years.

• The groin swelling is usually slow growing, painful with exacerbations during menses.

• The incidence of inguinal endometriosis on the right side is 90–94% as compared to the left.

• Gynaecological assessment has to be carried out to rule out intrapelvic endometriosis before excision.