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Hematuria

Between 0.5% and 1% of all children may have microhematuria persisting for at least 1 month. Isolated hematuria is unaccompanied by proteinuria. Hematuria is defined as more than 5 to 10 RBCs per high-power microscopic field from a centrifuged midstream voided urine sample. The urine may be yellow, pink, red, brown, or smoky on gross examination. Hemoglobin and myoglobin will produce the same color changes on the dipstick as intact RBCs. A false-positive test for blood can result from the presence of drugs such as ascorbic acid, sulfonamides, iron sorbitol, metronidazole, and nitrofurantoin. Therefore, each urine sample that tests positive for blood by dipstick must be examined microscopically to confirm the presence or absence of intact hematuria, bloody urine, blood in urine.

TABLE 2 -- Differential Diagnosis of Persistent Hematuria

FAMILY HISTORY (TABLE 3)

A family history of hematuria without renal failure may be seen with thin basement membrane disease. A family history of hematuria, chronic renal failure, dialysis, or renal transplantation with bilateral deafness at an early age and ocular abnormalities strongly suggests Alport syndrome. An audiogram is indicated for children suspected of having Alport syndrome because high-tone hearing loss may not be apparent on the initial

TABLE 3 -- Familial Causes of Hematuria

areas of the urinary tract other than glomeruli will be normal in size or slightly small, with smooth or irregular edges (eumorphic). Nonglomerular bleeding usually is associated with normal urinary protein excretion and an absence of RBC casts.

Preliminary tests of urine and blood should include a urine culture, sickle cell preparation in African-American children, urinary calcium: urinary creatinine ratio, serum creatinine, C3, and streptozyme titer. Ultrasonography of the kidneys and urinary bladder is recommended to rule out polycystic kidney disease, tumor, ureteropelvic junction obstruction, and stones.

The presence of proteinuria (>1+ on dipstick) strongly suggests glomerulonephritis or intrinsic renal disease as the etiology of the hematuria. The diagnosis of glomerulo-nephritis demands careful microscopic inspection of the urinary sediment for the presence of RBC casts. Demonstration of RBCs that have bizarre shapes, blebs, or burrs (dysmorphic RBCs) by phase-contrast microscopy closely correlates with a glomerular origin of the RBC.

If proteinuria is present on urinalysis, urinary protein excretion should be measured by a timed 12- or 24-hour urine collection or a urine protein:urine creatinine ratio on a single voided sample. Protein excretion of less than 4 mg/m² per hour is normal; more than 40 mg/m² per hour is considered in

Hematuria and Hypercalciuria

A frequent cause of isolated hematuria, especially in the southwestern United States, is idiopathic hypercalciuria (urinary calcium:urinary creatinine ratio of >0.21 and 24-hour urinary calcium excretion of >4 mg/kg). Approximately 30% of children referred for evaluation of isolated hematuria have idiopathic hypercalciuria as the etiology. Other conditions that may cause hypercalciuria include hyperparathyroidism, immobilization, vitamin D intoxication, and furosemide use. Renal ultrasonography and plain abdominal radiography are helpful in ruling out the presence of nephrocalcinosis or nephrolithiasis.

Gross Hematuria

The reported incidence of gross hematuria is approximately 1 in 1,000 visits to a pediatric emergency facility. Urinary tract infection is the most frequent cause of hematuria, followed by perineal irritation, meatal stenosis with ulceration, trauma, recent surgical procedure, clotting abnormalities, nephrolithiasis, and glomerulonephritis. In adolescents with gross hematuria, the most common (52%) pathologic diagnosis is IgA nephropathy.

Gross hematuria in patients who have IgA nephropathy usually is associated with viral upper respiratory tract infections or gastroenteritis. The presence of RBC casts and proteinuria in this patient group requires a diagnostic renal biopsy. Approximately 15% of children who have isolated, persistent hematuria for more than 12 months' duration will have IgA nephropathy.

Less frequently observed causes for gross hematuria, such as pelvocalyceal or urethral diverticulae, bladder stones or tumors, polyps, foreign bodies, and other developmental genitourinary abnormalities, must be considered. Intravenous pyelography, renal scan, computed tomography, magnetic resonance imaging, renal arteriography, renal biopsy, and cystoscopy may be required in patients who have unexplained gross hematuria to 

TABLE 4 -- Renal Structural Abnormalities Associated With Hematuria

If isolated hematuria persists for 1 year or more, consultation with a pediatric nephrologist to assess the need for a renal biopsy is