Recently, we often see small infants and toddlers in the clinic for checkups or other illnesses, and urine tests reveal the presence of dozens or tens of urine leukocytes, dozens or tens of red blood cells, or possibly a small amount of proteinuria, often without symptoms, or some of them show frequent urination, painful urination, vulvar flushing, etc. These children do not have high blood inflammatory indicators, and no bacterial growth is found in urine cultures. The most common cause of hematuria and leukocyturia in young infants and toddlers is urinary tract infections. Typical urinary tract infections often cause fever, significantly elevated inflammatory indicators in the blood, and urine tests can all reach hundreds or thousands of white blood cells, and if urine cultures are further examined, they are often found to be positive for bacteria.