Pedunculated and Obstructive Wilms' Tumor: A Rare Presentation in a 2 Year-old Male

Wilms' tumor manifesting as an obstructing ureteral mass is extremely rare. Herein, we report an unusual case in which a child presented with a clinical picture concerning for and suggestive of ureteropelvic junction obstruction (UPJO), but was instead found to have an intrapelvic pedunculated Wilms' tumor with extension into the proximal ureter. We discuss the patient's diagnostic workup, radiographic, operative and pathologic findings, as well as important lessons learned from this unusual case.