What is the initial lab workup for a patient presenting with hematuria (blood in urine)?

Initial Laboratory Workup for Hematuria

The initial laboratory workup for a patient presenting with hematuria should include comprehensive urinalysis with microscopic examination, urine culture, serum creatinine measurement, and assessment for proteinuria. 1

Step-by-Step Laboratory Evaluation Algorithm

1. Comprehensive Urinalysis

• Quantify red blood cells per high-power field
• Examine red blood cell morphology (dysmorphic vs. normal)
• Look for red cell casts
• Test for proteinuria
• Assess for pyuria and bacteriuria

2. Additional Initial Laboratory Tests

• Serum creatinine to assess renal function
• Urine culture to rule out infection
• Urine protein quantification (if proteinuria is detected)

3. Specialized Testing Based on Initial Findings

If signs of glomerular bleeding are present:

• Presence of dysmorphic RBCs (>80% suggests glomerular source)
• Red cell casts
• Significant proteinuria (>500 mg/24 hours)
• Elevated serum creatinine

Then perform:

• 24-hour urine protein collection
• Tests for systemic diseases (lupus, vasculitis, hepatitis)
• Consider nephrology referral

If no signs of glomerular bleeding:

• Voided urinary cytology (for patients with risk factors for transitional cell carcinoma)
• Risk factors include: age >40 years, smoking history, occupational exposure to chemicals/dyes, history of gross hematuria, irritative voiding symptoms 1

Key Distinctions in Laboratory Approach

For Microscopic Hematuria

• Complete the laboratory workup as outlined above
• If infection is suspected, repeat urinalysis 6 weeks after treatment
• No additional evaluation needed if hematuria resolves after treating infection 1

For Gross Hematuria

• More urgent and complete evaluation required due to higher risk of malignancy (30-40%)
• Same initial laboratory tests but expedited imaging and specialist referral 1

Important Clinical Considerations

• Dysmorphic RBCs suggest glomerular origin while normal "doughnut-shaped" RBCs suggest lower urinary tract bleeding 1
• The presence of significant proteinuria (>1,000 mg/24 hours) with hematuria strongly suggests renal parenchymal disease 1
• Urine cytology has limited utility in the initial evaluation of microscopic hematuria and may be omitted in low-risk patients 2, 3
• Persistent hematuria after negative initial evaluation requires continued monitoring 1

Common Pitfalls to Avoid

• Failing to repeat urinalysis after treating UTI to confirm resolution of hematuria
• Overlooking the significance of dysmorphic RBCs and red cell casts
• Neglecting to measure serum creatinine in all patients with hematuria
• Assuming interstitial cystitis as the cause of hematuria without proper evaluation, especially in women with chronic pelvic pain 1, 4
• Relying solely on urine cytology for cancer detection, as its sensitivity is limited, particularly for low-grade tumors 2, 3

Remember that this laboratory workup is just the first step in a comprehensive evaluation that may require imaging studies and cystoscopy based on laboratory findings and risk factors for urologic malignancy.