A ureterocele is a congenital abnormality found 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 ureturs 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.

Since the advent of the ultrasound, most ureteroceles is diagnosed prenatally. The pediatric and adult conditions are often found only through diagnostic imaging performed for reasons other than suspicious ureteroceles. The signs and symptoms of ureteroceles in the latter two forms can easily be confused with other medical conditions. Symptoms can include:

• Frequent urinary tract infection
• Urosepsis
• Obstructive voiding symptoms
• Urinary retention
• Failure to thrive
• Hematuria
• Cyclic abdominal pain
• Ureteral calculus

Many other complications arise from ureteroceles. Redundant collection systems are usually smaller in diameter than single, and predispose the patient to impassable kidney stones. The effective "bladder within a bladder" compounds this problem by increasing the collision of uric acid particles, the process by which uric acid stones are formed. Ureteroceles is also associated with poor kidney function. It can cause frequent blockage of the ureter leading to serious kidney damage. In other cases, a small, upper portion of the kidney is congenitally non-functional. Though often benign, this problem can necessitate the removal of non-functioning parts.

Definitive causes of ureteroceles have not been found. While the abnormal growth occurs within the womb, it has not been substantiated that genetics are to blame.