Primary umbilical endometriosis masquerading as strangulated umbilical hernia: a diagnostic pitfall.

Primary umbilical endometriosis (Villar's nodule) is a rare entity, representing 0.5%-1% of all endometriosis cases. We report a 37-year-old multiparous woman presenting with a 7-day history of umbilical pain, swelling, and constipation. Examination revealed a 2 × 2 cm hyperpigmented, firm, and tender umbilical nodule. The patient described cyclic umbilical pain over 5 months associated with an irregular menstrual cycle. Trans-abdominal ultrasound suggested an incarcerated umbilical hernia, leading to emergency surgery. Intraoperatively, a small hernial defect containing extraperitoneal fat and a separate subcutaneous nodule were identified without strangulation. Excisional biopsy of the nodule with primary hernia repair was performed. Histopathology demonstrated endometrial glands and stroma within fibroconnective tissue, confirming primary umbilical endometriosis. The postoperative course was uneventful, and the patient remained asymptomatic at 4-month follow-up. This case highlights diagnostic difficulty when umbilical endometriosis presents as a surgical emergency and emphasizes the importance of surgical excision with histopathological confirmation.