TOW #46: Hematuria

Until recommendations changed in 2008, pediatricians routinely performed urinalysis screening in otherwise healthy children. This is no longer recommended, so we may not encounter microscopic hematuria quite as often. However, knowledge of how we approach hematuria in the outpatient setting is helpful to review given the possibility of medical complications.

Materials for this week:

Take-home points for this week on hematuria (for this,focused on the heme part, but case also reviews the protein part):

  1. Definition of hematuria: presence of 5 or more RBCs per high-power (40) field in 3 consecutive fresh, centrifuged specimens obtained over several weeks. There is microscopic (visible only on testing) or macroscopic (gross) hematuria (visible to the eye). Beware of false hematuria from drugs, foods (e.g.,beets, blackberries), toxins (e.g., lead), and urate crystals in newborns.
  2. Epidemiology: population studies in Finland and Texas have shown a prevalence of 3-6% of asymptomatic microscopic hematuria in school-age children in a single urine sample. With repeat screenings, prevalence declines to 0.5% to 1%. There are no differences by race/ethnicity. Until 2008, the AAP recommended urine screening routinely at age 5 and during adolescence, but this was ended due to low rates of disease and high false positives.
  3. Types of hematuria: Diagnostic evaluation depends on the category: gross hematuria, symptomatic microscopic hematuria, asymptomatic microscopic hematuria with proteinuria, or isolated asymptomatic microscopic hematuria. Evaluating RBC morphology helps distinguish glomerular and extraglomerular sources. Glomerular bleeding is typically “cola-colored,” with RBC casts and distorted RBC morphology.
  4. Hematuria type determines need for work-up: see the above algorithm. We have to distinguish between asymptomatic microscopic hematuria which is usually benign and requires conservative management, and hematuria with accompanying proteinuria, edema, hypertension, or other symptoms which suggests underlying renal disease. Underlying causes of gross hematuria are identified in 56% of cases including UTI, trauma, kidney stones, hypercalciuria, coagulopathy and kidney disease.
  5. Initial next steps: Repeat the urine test with microscopy, identify other symptoms, and review family history of renal disease. For persistent proteinuria, a morning and evening urine will be needed to identify orthostatic proteinuria, which accounts for 60% of asymptomatic proteinuria cases. If the patient has any markers of serious glomerular pathology, a basic metabolic panel, CBC, C3, C4, albumin, ANA, anti-streptolysin (ASO) and anti-DNAse B titers, and streptozyme would be recommended.

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