Chapter 23 HEMATURIA, MICROSCOPIC

Theodore X. O’Connell

Microscopic hematuria is much more common than gross hematuria in children, with a prevalence of 3% to 4% in a single urine sample and 1% to 2% in two or more urine samples. There is no consensus on the definition of microscopic hematuria, although more than 5 to 10 red blood cells (RBCs) per high-power field is considered significant. It is generally recommended that at least two of three uninalyses show microscopic hematuria over 2 to 3 weeks before further evaluation is performed. No consensus exists on a stepwise evaluation, but this chapter provides an approach to the evaluation of the child with microscopic hematuria.

Hematuria may originate from the glomeruli, renal tubules and interstitium, or urinary tract, which includes the collecting systems, ureters, bladder, and urethra. In children, the source of bleeding is most often from the glomeruli. In most cases, proteinuria, RBC casts, and dysmorphic RBCs in the urine accompany hematuria caused by glomerulonephritis. The most common causes of persistent microscopic hematuria in children include glomerulopathies (e.g., IgA nephropathy, thin basement membrane disease), Alport syndrome, hypercalciuria, and urinary tract infection (UTI).

The presence of hematuria must be confirmed by microscopic examination of the spun sediment of urine because other substances besides blood can give a false-positive dipstick test for blood. The dipstick and microscopic urinalysis should be repeated twice within 2 weeks after the initial specimen. If the hematuria resolves, no further tests are needed. If persistent microscopic hematuria is confirmed, a thorough history (with particular attention to the family history) and physical examination should be performed.

Two diagnostic tests should be performed: a test for proteinuria and a microscopic examination of the urine for RBCs and RBC casts. Proteinuria usually does not exceed 2+ (100 mg/dL) if the only source of protein is from the blood. Patients with 1+ to 2+ proteinuria should be evaluated for orthostatic proteinuria. A patient with more than 2+ proteinuria should be evaluated for glomerulonephritis and nephrotic syndrome. The presence of RBC casts is a highly specific marker for glomerulonephritis. In addition to these tests, many authorities also recommend urine culture, urine calcium-to-creatinine ratio, and renal ultrasound examination for confirmed cases of microscopic hematuria.

Microscopic hematuria that persists falls into one of three categories: asymptomatic isolated microscopic hematuria, asymptomatic microscopic hematuria with proteinuria, and symptomatic isolated microscopic hematuria.

Asymptomatic isolated microscopic hematuria is common in children. Many experts recommend observation of these children if the examination is normal, with further evaluation only if proteinuria, hypertension, or gross hematuria is present. In the child with asymptomatic isolated microscopic hematuria, the early morning urinalysis should be repeated weekly for 2 weeks with no exercise before the collection of the urine sample. If the hematuria persists, urine culture should be obtained and, if positive, the patient should be treated with antibiotics. If the urine culture is negative, the patient should be followed up every 3 months with a history, physical examination, blood pressure measurement, and urinalysis. If the hematuria persists for 1 year, measurement of the urine calcium-creatinine ratio should be obtained, and the parents and siblings should be tested for hematuria. Hemoglobin electrophoresis should be performed if sickle cell trait is a consideration. Figure 23-1 provides an algorithm for the evaluation of a child with asymptomatic microscopic hematuria.

Figure 23-1 Evaluation of a child with asymptomatic microscopic hematuria.

(From Patel HP, Bissler JJ. Hematuria in children. Pediatr Clin North Am 2001;48:1519–1537, with permission.)

Asymptomatic microscopic hematuria with proteinuria is associated with a higher risk for significant renal disease. In this case, urinary protein excretion should be quantified. If protein excretion is greater than 4 mg/m² per hour or the urine protein-to-creatinine ratio is greater than 0.2 mg protein per milligram of creatinine in children older than 2 years or greater than 0.5 mg of protein per milligram of creatinine in younger children, the patient should be referred to a pediatric nephrologist. If urinary protein excretion is less than these values, the patient should be reevaluated in a few weeks. If the hematuria and proteinuria have resolved, no further evaluation is indicated. If there is only asymptomatic microscopic hematuria, the patient may be monitored as for asymptomatic isolated microscopic hematuria. If the hematuria and proteinuria persist, the patient should be referred to a pediatric nephrologist. Additional testing is outlined below. Figure 23-2 provides an algorithm for the evaluation of a child with microscopic hematuria associated with proteinuria, symptoms, or abnormalities in history or physics examination.

Figure 23-2 Evaluation of a child with microscopic hematuria associated with proteinuria, symptoms, or abnormalities in the history or physical examination.

(From Patel HP, Bissler JJ. Hematuria in children. Pediatr Clin North Am 2001;48:1519–1537, with permission.)

Symptomatic microscopic hematuria may manifest with fever, weight loss, malaise, rash, arthritis, edema, hypertension, dysuria, or oliguria. The presence of these symptoms suggests a systemic process or significant disease affecting the urinary tract. History and physical examination may provide important clues to the diagnosis. The laboratory evaluation includes serum creatinine, blood urea nitrogen (BUN), electrolytes, complete blood count (CBC), C3, C4, and albumin. Additional testing to consider is outlined below. Important causes of symptomatic microscopic hematuria include acute postinfectious glomerulonephritis, hemolytic-uremic syndrome, Henoch-Schönlein purpura, menbranoproliferative glomerulonephritis, IgA nephropathy, and focal segmental glomerulosclerosis.