A ureterocele is a swelling at the bottom of one of the tubes
(ureters) that carry urine from the kidney to the bladder. The
swollen area can block urine flow. A ureterocele is a birth
defect. Causes, incidence, and risk factors A ureterocele occurs
in the lower part of the ureter, where the tube enters the
bladder. The swollen area prevents urine from moving freely into
the bladder. The urine collects in the ureter and stretches its
walls, blowing it up like a water balloon. A ureterocele can
also cause urine to flow backward from the bladder to the
kidney. This is called reflux. Ureteroceles occur in about 1 in
500 to 1 in 4,000 people. Caucasians are most likely to be
affected. Ureteroceles are equally common in left- and right-
side ureters. Signs and tests Large ureteroceles are usually
diagnosed earlier than smaller ones. A ureterocele may be
discovered before the baby is born (during a pregnancy
ultrasound Some people with ureteroceles do not know they have
the condition. Often, the diagnosis is made la