Severe ureteropelvic junction obstruction with massive hydronephrosis causing compression of the inferior vena cava.

A 7-week-old girl presented with tachypnea and abdominal distension. Abdominal ultrasonography demonstrated a 16 cm cystic mass in the right abdomen. Contrast-enhanced T2-weighted magnetic resonance imaging revealed severe hydronephrosis of the right kidney with thinning of the renal parenchyma consistent with a massive ureteropelvic junction (UPJ) obstruction. A percutaneous nephrostomy tube was placed for decompression of her right kidney and 1270 ml of fluid was drained. The patient underwent an open pyeloplasty. Her follow-up renal ultrasonography demonstrated resolution of her severe hydronephrosis.