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Kidney or Urinary Tract Disorders
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APPROACH TO THE CHILD WITH HEMATURIA
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Hematuria is a common sign of urinary tract disease but also occurs in otherwise healthy children. Hematuria can present as either discolored red, brown, or tea-colored urine, or it can present as yellow urine with a positive dipstick for blood. Clues to the diagnosis may be obtained from a history focused on whether the hematuria is painless, intermittent, or persistent, or microscopic or gross. A family history of hematuria or renal disease is important. Brown or tea-colored urine is common in glomerulonephritis, whereas red or obviously bloody urine suggests postglomerular bleeding. Glomerulonephritis is commonly associated with other abnormalities of the urine such as proteinuria and cellular casts as well as hypertension, edema, and reduced renal function. Table 464-1 provides a simple mnemonic for the causes of hematuria. A diagnostic approach and differential diagnosis for discolored urine and microscopic hematuria are shown in Figure 464-1.
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Microscopic hematuria, defined as the presence of a positive urine dipstick for blood and more than 5 red blood cells (RBCs) per high-power field (hpf) on centrifuged urine, occurs in approximately 1% of school-age children on at least 1 urine sample. About 0.5% will continue to have hematuria on 2 of 3 samples, and a third have hematuria on 3 samples. Fewer than one-third of patients diagnosed with hematuria demonstrate hematuria 1 year later. Only a very small number of children with microscopic hematuria had significant renal or urologic disease. Microscopic hematuria can occur following vigorous exercise; thus, it is common in school-age children and, in the majority of cases, is benign.
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Hypercalciuria, defined as more than 4 mg of urinary calcium/kg/d, has been found in significant numbers of children with microscopic hematuria. This association is even stronger if there is a family history of stone disease or the occurrence of gross hematuria. The calcium-to-creatinine (Ca/Cr) ratio can be used to screen for hypercalciuria; for children or adolescents, a urinary Ca/Cr ratio greater than 0.2 is abnormal.
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The value of urinary tract imaging in children with microscopic hematuria is controversial. The yield of routine ultrasound is low, and reported findings are frequently of little clinical significance. When microscopic hematuria persists for several months, decisions on the need for urinary tract imaging are made based on other concerns. Voiding cystourethrograms and cystoscopy are rarely helpful ...