Unexpected Adnexal Torsion and Hemoperitoneum Caused by Spontaneous Ovarian Parasitic Leiomyoma: A Case Report.

Parasitic myomas (PMs) are rare uterine leiomyomas that exist independently of the uterus. They can result from tissue fragments left behind during laparoscopic uterine procedures or, less commonly, develop spontaneously from pedunculated subserosal leiomyomas that detach and revascularize on extrauterine structures. We present a case of a 37-year-old woman with a history of pedunculated subserosal leiomyoma who presented in the emergency department with acute pelvic pain. Imaging revealed a large pelvic mass separated from the uterus and significant hemoperitoneum. Emergency laparotomy was performed, identifying a large left adnexal mass causing adnexal torsion, with partial pedicle rupture as the bleeding source. Histopathology confirmed a benign leiomyoma in the ovarian parenchyma. This case underscores the importance of considering PMs in the differential diagnosis of acute pelvic pain and provides more insight about the etiology of spontaneous PMs, which are rare entities.