What other labs and tests are used to evaluate hematuria (blood in urine)?

Laboratory Tests and Diagnostic Evaluation for Hematuria

The comprehensive evaluation of hematuria requires specific laboratory tests including urinalysis with microscopic examination, serum creatinine, and appropriate imaging studies, with urologic referral for cystoscopy in cases without a benign cause. 1, 2

Initial Laboratory Evaluation

• Confirm heme-positive dipstick results with microscopic urinalysis showing ≥3 red blood cells per high-powered field before initiating further evaluation 1
• Complete urinalysis with microscopic examination should assess:
  • Number of red blood cells per high-power field
  • Presence of dysmorphic red blood cells or red cell casts (suggesting glomerular source)
  • Presence of white blood cells or bacteria (suggesting infection)
  • Degree of proteinuria 1, 2
• Urine culture to rule out urinary tract infection 2, 3
• Serum creatinine measurement to assess renal function 1, 2

Determining Source of Hematuria

Glomerular Source Indicators

• Significant proteinuria (>500 mg/24 hours)
• Dysmorphic RBCs (>80% dysmorphic)
• Red cell casts
• Elevated serum creatinine 2, 4

Non-Glomerular (Urologic) Source Indicators

• Normal-shaped RBCs (>80% normal)
• Minimal or no proteinuria (<500 mg/24 hours)
• Normal serum creatinine 2, 4

Additional Laboratory Tests

• 24-hour urine collection for protein quantification if dipstick shows ≥1+ protein 4, 5
• BUN (blood urea nitrogen) and complete blood count 5
• Do not obtain urinary cytology or other urine-based molecular markers for bladder cancer detection in the initial evaluation of hematuria 1

Imaging Studies

• CT urography is the preferred imaging modality for comprehensive evaluation of the upper urinary tract 2, 4
• MR urography is an alternative if CT is contraindicated 2
• Renal ultrasound with retrograde pyelography can be considered if CT and MR are not feasible 2

Specialist Referral

• Urologic referral is necessary for:
  • All patients with gross hematuria (even if self-limited)
  • Patients with microscopic hematuria without a benign cause
  • Patients with risk factors including smoking history or occupational exposures 1, 2
• Nephrology referral is recommended if there is evidence of glomerular disease:
  • Proteinuria >1,000 mg/24 hours
  • Proteinuria >500 mg/24 hours that is persistent or increasing
  • Red cell casts
  • Predominantly dysmorphic RBCs 2, 4

Follow-up Recommendations

• For patients with negative initial evaluation but persistent hematuria:
  • Repeat urinalysis at 6,12,24, and 36 months
  • Monitor blood pressure
  • Consider nephrology referral if hematuria persists with development of hypertension, proteinuria, or evidence of glomerular bleeding 2, 4

Important Caveats

• Do not attribute hematuria solely to antiplatelet or anticoagulant therapy without further investigation 1, 2
• In women, obtain a catheterized specimen if clean-catch cannot be reliably obtained due to vaginal contamination 1, 4
• Painless gross hematuria has a stronger association with cancer than hematuria accompanied by flank pain 1, 2
• Patients with microscopic hematuria, negative urologic evaluation, and no evidence of glomerular bleeding have low risk for progressive renal disease but should still be monitored 1, 4