Review Question - QID 213414

A 32-year-old female is brought to the emergency room by her friend for acute onset abdominal pain. She states that she was in a kickboxing class when she suddenly developed left-sided abdominal pain. Her past medical history is significant for chlamydia. She is currently sexually active and does not use contraception. Her menstrual periods occur regularly every 30 days. Her last menstrual period ended 2 days ago. The patient’s temperature is 99°F (37.2°C), blood pressure is 110/68 mmHg, pulse is 88/min, and respirations are 14/min with an oxygen saturation of 98% on room air. On physical exam, there is left-sided, lower abdominal tenderness and guarding. Pelvic examination is notable for clear mucous in the vaginal introitus and tenderness of the left adnexa. A pelvic ultrasound with Doppler reveals a large amount of fluid in the rectouterine pouch. Which of the following is the most likely diagnosis?