Botryoid nephroblastoma with pelviureteral and vesical extension mimicking xanthogranulomatous pyelonephritis in children

We report the case of a multicystic renal lesion in a nine-month-old boy, who presented clinically with a left sided flank mass, fever and biological signs of urinary tract infection. The initial sonographic examination revealed an enlarged left kidney showing multiple anechoic fluid-filled formations and a distended left pelviureteral tract with solid appearing luminal echo pattern. Later, CT scan supported these aspects. Our first hypothesis was an inflammatory process such as xanthogranulomatous pyelonephritis. Nevertheless, final histological analysis diagnosed a nephroblastoma with cysts formation. This case highlights one unusual radiological appearance of nephroblastoma, which may result in misdiagnosis.