Aim: Cystic echinococcosis most commonly involves the liver and lungs in childhood, whereas urinary system involvement is rare. Renal hydatid disease, especially with ureteral extension, may cause significant diagnostic and therapeutic challenges. We aimed to present a pediatric case with advanced hydatid disease involving the left kidney and extending along the ureter, resulting in loss of renal function, and to discuss the clinical, radiological, and surgical management of this rare localization.
Case: A 12-year-old girl presented with intermittent left flank pain for one year. Ultrasonography performed at an outside center revealed grade 4 hydronephrosis and a cystic lesion in the left kidney, and she was referred to our clinic. Physical examination showed left costovertebral angle tenderness without dysuria. Ultrasonography in our institution demonstrated 75×63 mm cystic lesion containing internal vesicle-like structures in the left kidney. Computed tomography revealed a lesion in the lower pole of the left kidney compatible with hydatid cyst, classified as stage 3b according to the World Health Organization (WHO) classification and stage 3 according to the Gharbi classification. Multiple cystic semisolid lesions within the left ureter lumen and diffuse ureteral dilatation suggested ureteral extension of the disease. ELISA IgG for hydatid cyst was positive (1/640), and albendazole therapy was started. Due to elevated C-reactive protein and leukocyte levels, ceftriaxone was added. Urinalysis showed leukocyturia without scolices. MAG-3 scintigraphy demonstrated no functional uptake in the left kidney, and nephroureterectomy was planned.
Conclusion: Urinary system hydatid disease is rare, but advanced cases may cause severe hydronephrosis and irreversible loss of renal function due to ureteral involvement. Radical surgery may be required in patients with a nonfunctioning kidney and extensive ureteral spread. Nephroureterectomy can be a safe and effective treatment option in selected cases. Early diagnosis and appropriate surgical planning are essential to reduce morbidity.

