Pelvic Actinomycosis Mimicking Gynecologic Malignancy: CT and Histopathologic Correlation

A healthy 65-year-old postmenopausal woman with a 15-year history of copper intrauterine device use presented to the emergency room with several days of lower abdominal pain and diarrhea. Laboratory testing revealed leukocytosis (white blood cell count, 26.15 × 10³/µL) and elevated C-reactive protein (19.81 mg/dL). Contrast-enhanced computed tomography demonstrated multiple cystic and heterogeneous abdominopelvic lesions, including extension across the abdominal wall fascia and muscles, with involvement of the uterus and urinary bladder, raising suspicion for advanced gynecologic malignancy with peritoneal dissemination. Tumor markers were within normal limits. Persistent lower abdominal pain and inflammatory markers without fever and negative blood culture after a week of empirical antibiotics (Flomoxef Sodium 2000 mg) prompted exploratory laparotomy to evaluate for possible ovarian malignancy or abscess. Total hysterectomy, right salpingo-oophorectomy, partial excision of the abdominal abscess, and drainage of the left ovarian abscess were performed. Histopathology later confirmed the diagnosis of diffuse pelvic actinomycosis. The patient recovered after surgical drainage and antibiotics penicillin G for 4 weeks, followed by doxycycline (200 mg) twice daily for 3 months. This case highlights the important radiologic features of pelvic actinomycosis mimicking gynecologic malignancy, particularly in women with prolonged intrauterine device use and the management in refractory pelvic actinomycosis.