A ureterocele is a cystic outpouching of the distal ureter into the urinary bladder. Ureteroceles occur in approximately 1 in 4000 children with increased incidence among patients of Northern European descent and females (4-7 times the risk of males). Autopsy studies demonstrate a higher incidence, estimated as 1:500 patients, many of whom are asymptomatic. A slight left-sided predominance exists, with 10% of ureteroceles being bilateral.

In the pediatric population, ureteroceles are most commonly diagnosed on prenatal ultrasounds. Symptomatic infants may present with urinary tract infections (UTIs) or failure to thrive. Most patients with ureteroceles have ipsilateral hydronephrosis and/or dysplastic kidney.

Adult ureteroceles are typically found incidentally and are usually asymptomatic. As in children, symptomatic ureteroceles can result in UTIs, urinary retention, or hematuria. Ureteroceles can be classified by anatomic location and number based on the following system:

• Single system – Single kidney, collecting system, and ureter.
• Duplex system – Kidneys that have completely duplicated ureters.
• Orthotopic (intravesical) – Ureterocele contained within the bladder that may prolapse into and beyond the bladder neck and usually arises from a single renal unit with one collecting system. More commonly diagnosed in adults.
• Ectopic (extravesical) – Ureteroceles with tissue that originates at the bladder neck or beyond and typically arises from the upper pole moiety of a duplicated collecting system. More common in the pediatric population.

The pathogenesis of ureteroceles is unknown; however, it is presumed that the defect occurs during embryonic development.