A patient has intermittent right lower quadrant pain; pelvic ultrasound shows a cystic ovarian mass. What is the diagnosis?

• A. Ovarian cyst rupture
• B. Intermittent ovarian torsion
• C. Ectopic pregnancy
• D. Pelvic inflammatory disease

Answer: (B)

Intermittent ovarian torsion explains recurrent unilateral pelvic pain in the setting of an ovarian mass because twisting of the ovary around its blood supply can occur, then spontaneously detorse, producing pain that waxes and wanes. A cystic ovarian mass provides a lead point that makes twisting more likely, so intermittent torsion fits the ultrasound finding and the clinical pattern of episodic pain.

Ovarian cyst rupture usually causes sudden, sharp pain with possible peritoneal signs and often demonstrates free fluid on imaging. An ectopic pregnancy would be suspected if pregnancy testing is positive and the ultrasound shows an ectopic gestation rather than a simple cystic ovarian mass. Pelvic inflammatory disease typically presents with fever, bilateral lower abdominal pain, and cervical motion tenderness, with ultrasound showing tubo-ovarian inflammation rather than a solitary cystic ovarian mass.