We report here the rare case of a 28-year-old woman with a large hydatid cyst in her left lower pelvis with an unusual sonographic presentation mimicking a multicystic ovarian tumor. Laparoscopic evaluation revealed normal uterus and ovaries with a swelling in the left retropritoneal area. We decided to reach this tumour by the vaginal route and multiple scolex, daughter cysts were removed via a left lateral vaginal wall incision. The pericystic cavity was thoroughly washed. The patient was discharged on the first postoperative day. Mebendazole (100 mg twice daily) was administered for 4 months. This parasite should be kept in mind and considered when making the differential diagnosis of pelvic cystic masses, particularly if the patient is from an endemic area.

Keywords: Echinococcus, hydatid disease, ovarian tumour