A ureterocele is a congenital abnormality foun in the urinary bladder. In this condition called ureteroceles, the distal ureter balloons at its opening into the bladder, forming a sac-like pouch. It is most often associated with a double collector system, where two ureters drain their respective kidney instead of one. Simple ureteroceles, where the condition involves only a single ureter, represents only twenty percent of cases. Ureteroceles strikes only one in 4,000 individuals, at least four fifths of whom are female. Patients are frequently Caucasian.