Urine retained in the kidneys damages kidney tissue by stretching and thinning the organ. Such damage can lead to kidney stones and scarring, reducing kidney function. Urine in the kidneys can lead to infection. In the case of reflux, a bladder infection will immediately move from the bladder into the kidney.
Our first referral to a urologist led to a fairly uncomfortable test called VCUG. Using a catheter, they pump his bladder full of dye while under an x-ray machine. Once the bladder is very full, they remove the catheter and image his urinary system while he evacuates the liquid. This test would show them all of the tubes involved in the process and let us know where that urine ends up. That test would tell us the most likely cause. We also had to know whether he was getting better (less urine was in the kidney), staying the same (urine content in the kidney stays static), or if it was getting worse (kidney continues to fill even more with urine). That meant an additional ultrasound a month after the first to check the size of the dilation in his kidney.
What I found really funny is that I stopped taking him to any of the pediatric urologist appointments. Everything the doctor needed to know about was tucked away inside my little one's body cavity and as long as the doctor had the x-ray or ultrasound results he knew everything he could about the state of the condition.