In children, a voiding cystourethrogram is often recommended after a urinary tract infection to check for a condition known as vesicoureteral (VU) reflux.
Urine is produced in the kidneys and flows through the ureters into the bladder. A valve mechanism prevents urine from backing up into the kidneys as the bladder gets full. Upon urination, urine leaves the bladder through the urethra and is eliminated from the body.
In some children, an abnormality in the valve or the ureters allows urine to flow backwards into the ureters, referred to as VU reflux. In mild cases, urine backs up into the lower ureter. In severe cases, it can back up into a swollen kidney.
Usually, children with this condition are born with it. Other causes can include blockage to the bladder, abnormal urination with very high pressure within the bladder, incomplete emptying of the bladder, or urinary tract infections. Reflux is commonly associated with urinary tract infections, occurring in about 40 percent of newborns and infants, and 25 percent of older children. Urinary tract infection may be the only symptom of the problem.