My 7 year old son, once while playing he complined of severe stomach pain. Later while passing urine there was some blood, i got really panicked and went to see a child doctor. the doctor asked me to get the urine examaintion done. The urine test showed there was lot of ous cells. The doctor explined presence of pus cells means there will be lot of urine infection. Doctor gave him some antibiotics and now he is fine. Why he got this infection, i really donot know ?