Periodic Abdominal Pain: Response to NSAIDs Hides the Diagnosis.

: A 17-year-old African-American patient presented to the emergency department with acute onset of severe, constant, lower abdominal pain that radiated to the lower back. The only associated symptom was nausea. She has been taking ibuprofen for a previously diagnosed chronic dysmenorrhea and had had good response to therapy. Rectovaginal examination revealed a tender mass in the cul de sac. Pelvic ultrasound led to the presumptive diagnosis of endometriomas, but could not exclude ovarian neoplasms. Urgent surgery revealed both left and right 3 x 6 cm ovarian cysts containing red to brown fluid, consistent with endometriomas. Postoperative course was uncomplicated.