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Hematuria is the presence of blood in the urine. Gross hematuria is defined as hematuria visible to the patient or caregivers.  Microscopic hematuria is defined as identification of red blood cells under the microscope on at least 2 consecutive samples.  Microscopic hematuria occurs in 1% of children.  Hypercalciuria (high concentration of calcium in the urine) is the most common underlying diagnosis of microscopic hematuria.  However, no diagnosis is found in up to 80% of children with microscopic hematuria and 38% of children with gross hematuria.  If the evaluation is negative, the parents should be informed that the likelihood of serious renal disease in the child is low.