Primary umbilical endometriosis mimicking a urachal fistula: a case report

BackgroundUmbilical endometriosis is an uncommon form of extrapelvic endometriosis and may be misdiagnosed as other umbilical or urachal disorders. Cyclic umbilical bleeding or discharge is an important clinical clue, but the diagnosis is often confirmed only after surgical excision and histopathological examination.Case presentationA 31-year-old woman presented to the hospital with a history of umbilical discharge for more than one year. The symptom occurred predominantly during menstruation and was characterized by recurrent umbilical discharge with occasional bloody secretion. Physical examination revealed mild erythema and swelling of the umbilicus, without active discharge at the time of examination. Preoperative computed tomography of the lower abdomen and pelvis showed no obvious abnormality. The initial clinical diagnosis was urachal fistula with possible umbilical infection. The patient underwent surgical excision of the umbilical lesion under general anesthesia. Intraoperatively, purulent discharge was observed at the umbilicus, and complete excision of the umbilical lesion was performed. Histopathological examination revealed endometrial glands and stroma beneath the squamous epithelium with hemosiderin deposition, while immunohistochemistry showed CD10, CK7, and PR positivity with negative/weak ER expression, supporting the diagnosis of umbilical endometriosis.ConclusionThis case emphasizes the diagnostic challenge of primary umbilical endometriosis presenting with chronic umbilical discharge. Careful assessment of menstrual history, imaging findings, and pathological examination is essential for accurate diagnosis.