Ureterocele and pseudoureterocele: cobra versus cancer

The cobra-shaped distal ureter is not pathognomonic of a ureterocele. It may be seen with incomplete distal ureteral obstruction owing to tumor or calculus. The appearance of the wall surrounding the dilated distal ureteral segment is a more important finding to differentiate a ureterocele and a pseudoureterocele. The wall of a ureterocele is thin, while the lucency surrounding a pseudoureterocele is thicker and poorly defined.