A ureterocele is a balloon-like malformation occurring where the ureter, the tube that connects to the kidney, enters the bladder. This malformation blocks the normal flow of urine from the kidney, causing it to back up and accumulate in the ureter and the kidney. If this is not corrected, it can cause the kidney to cease functioning properly. The condition usually requires a simple operation shortly after birth to remove the blockage so that urine may freely drain into the bladder.