Giant Retroperitoneal Mass During Pregnancy With an Unexpected Diagnosis: Ovarian Cyst or Something Else?

Abdominal masses during pregnancy are uncommon and challenging to diagnose. Anatomical changes and imaging limitations often complicate evaluation. We present the case of a 30-year-old woman at 30 weeks of gestation who was admitted with progressive abdominal distension and discomfort. Initial ultrasound suggested a large ovarian cyst, but further imaging revealed a giant retroperitoneal mass. An exploratory laparotomy identified a cystic lesion over 25 cm in size containing approximately nine liters of citrine fluid. Partial resection was performed with preservation of maternal stability, and histopathology confirmed a benign suprarenal hydatid cyst. Postoperative recovery was favorable, and the pregnancy progressed without complications. At 39 weeks of gestation, the patient underwent cesarean section and delivered a healthy neonate. Both mother and child remained stable and were discharged in good condition. This case illustrates the importance of considering retroperitoneal pathology in the differential diagnosis of abdominal masses during pregnancy. Hydatid disease, although rare, should be considered in patients from endemic regions, particularly when imaging findings are atypical. Surgical management during pregnancy, while complex, can be safe and effective when conducted in an experienced, multidisciplinary setting.