URETEROCELE inflammation at the bottom of one of the ureters. It can be bilateral. The ureters are the tubes that carry urine from the kidney to the bladder. The inflamed area can obstruct the flow of urine. A ureterocele is a birth defect. A ureter occurs at the bottom of the ureter, where the duct enters the bladder. The inflamed area prevents urine from passing freely into the bladder. Urine collects in the ureter, stretches its walls and expands like a balloon with water. A ureterocele can also cause reflux, meaning urine is returned from the bladder to the kidney. Ureteroceles occur in about 1 in 500 people. This condition occurs equally in both left and right ureters. The ratio in women to men is 6:1 and occurs in each of 10 million children under the age of 6. .