Isolated retroperitoneal hydatid cyst in an 8-year-old girl: A case report

Introduction: Hydatid disease, caused by Echinococcus granulosus, typically affects the liver and lungs. Isolated retroperitoneal involvement is extremely rare, especially in children. Case presentation: An 8-year-old girl from a rural farming area presented with progressive right flank pain for three months and a history of livestock contact. Abdominal ultrasound revealed a 10 × 12 cm cystic lesion with a hyperechogenic membrane. Contrast-enhanced computed tomography (CT) further characterized the lesion, demonstrating a large (12 × 10 cm), multivesicular, multiseptated retroperitoneal cyst with a solid matrix containing multiple daughter cysts, consistent with World Health Organization (WHO) Informal Working Group on Echinococcosis classification of Type CE3b. The cyst was adherent to liver segment VI and extended directly into the renal parenchyma without pelvicalyceal communication. No other organ involvement was detected. Serology was positive for Echinococcus IgG by ELISA. Following seven days of preoperative albendazole (15 mg/kg/day), she underwent total nephron-sparing cystectomy with intraoperative sterilization using 20% hypertonic saline. The cyst contents, including multiple daughter cysts, were completely evacuated and the cyst wall excised. The procedure was uneventful aside from dense adhesions to the liver. Histopathology confirmed a hydatid cyst. Postoperative albendazole (15 mg/kg/day) was continued for three months, and at 12-month follow-up, no recurrence was observed. Conclusion: Hydatid cyst should be included in the differential diagnosis of children who have isolated retroperitoneal cysts.