Review Question - QID 211054

A 24-year-old woman presents to the emergency department with severe abdominal and lower back pain. She describes it as intense cramping and she experienced severe pain roughly 1 month ago that was similar. The patient's medical history is non-contributory, and her menses cause her to soak through 1 pad in a day. She is currently sexually active and does not use any contraception. Her temperature is 98.7°F (37°C), blood pressure is 117/68 mmHg, pulse is 79/min, respirations are 12/min, and oxygen saturation is 98% on room air. The patient's abdominal exam is non-focal, and her pelvic exam reveals no adnexal masses or tenderness and no cervical motion tenderness. Which of the following is the most likely diagnosis?