There is a lot we do not know about protecting the urinary tract from infection. Another suggestion is that the bladder does not empty smoothly, but mixed the urine around and this may prevent germs from being washed out properly. When germs stay in the bladder they can move up into the kidneys and cause infection there. Childrens bladders hold 20-50 ml whereas adult bladders hold 500 ml. This difference may make children more prone to infections than adults.
Urine infections are more common in uncircumcised boys than circumcised boys.
Vesicoureteric reflux often called bladder reflux, is a condition in which urine passes backwards up into the kidneys instead of passing out of the body with urination. About 30 percent of children with urine infections have bladder reflux. The urine that stays inside the body may become a pool for infection. Bladder reflux runs in families. And blockage of the urinary tract affects the flow of urine out of the body and can cause infection.