Ultrasound of the groin can be employed to evaluate for hernia; if a hernia has been excluded, histologic confirmation can be obtained via fine-needle aspiration of nodule contents.5,7 One caveat is that these tests are helpful only if the clinician suspects the diagnosis and orders them. The definitive diagnostic test remains direct visualization, which requires laparoscopy.1,5
Differential diagnosis
Lipoma was a favored diagnosis in this case because of the palpable, well-circumscribed borders, nontender on exam; intermittent, minimal tenderness; and no evidence of erythema or color change. A second possibility was an enlarged lymph node, which was less likely due to the location, large size, and sudden onset without any accompanying symptoms of infection or chronic illness. Finally, an inguinal hernia was least likely, again because of well-defined borders, no history of a lump in the area, a nodule that was not reducible, only minimal tenderness, and no color changes on the skin.
Management
Definitive treatment for inguinal endometriosis entails complete surgical excision.5-7 The provider should be prepared to repair a defect after the excision; there is potential for a substantial defect that might require mesh. Additionally, a herniorrhaphy may be indicated if there is a coexisting hernia.5 The risk for recurrent disease in the inguinal canal after treatment is uncommon, unless the excision was not complete.3
There is an association between inguinal and pelvic endometriosis but not a direct correlation. Data on concomitant pelvic and inguinal endometriosis have been variable. In one case series of 9 patients diagnosed with inguinal endometriosis, none had a history of pelvic endometriosis, and only 1 was subsequently diagnosed with pelvic endometriosis.7 An increased association was noted for patients with implants found on the proximal segment of the round ligament.7 However, implants on the extrapelvic segment were not likely to represent pelvic disease but rather isolated lesions in the canal.7 For those with pelvic endometriosis, complications and recurrence are likely, resulting in the need for long-term treatment.
There is some debate in the literature whether to proceed with laparoscopy once inguinal endometriosis has been identified. Diagnostic laparoscopy to evaluate the pelvis is indicated for symptomatic patients or for cases in which an indirect inguinal hernia is suspected.5 Laparoscopy can offer the benefit of both a diagnostic tool and a mechanism for treatment. However, this is an invasive procedure that also incurs risks. The medical provider, in discussion with the patient, must weigh the risks against the benefits of an invasive procedure before determining how to proceed.