What is the next step in evaluating a patient with microscopic hematuria (trace blood in urinalysis) and no other abnormalities?

Evaluation of Microscopic Hematuria

For patients with trace blood in urinalysis (microscopic hematuria) and no other abnormalities, referral to urology and complete urologic evaluation is recommended if the hematuria persists with >3 RBCs/HPF on two of three properly collected urinalyses. 1, 2

Risk Stratification

Patients with microscopic hematuria should be stratified into risk categories:

High-Risk Factors (requiring prompt evaluation)

• Age: women ≥50 years, men ≥40 years
• Smoking history >30 pack-years
• Gross hematuria or >25 RBC/HPF
• History of pelvic radiation
• Chronic urinary infections
• Occupational exposures to dyes, chemicals, etc. 1

Initial Evaluation

1. Confirm persistent hematuria:

   • Repeat urinalysis 2-3 times to confirm persistence
   • Hematuria is significant if >3 RBCs/HPF is present in 2 of 3 properly collected samples 2

2. Basic laboratory workup:

   • Complete blood count
   • Renal function tests (BUN, creatinine)
   • Urine culture to rule out infection 1

3. Assessment for glomerular disease:

   • Check for dysmorphic RBCs (>80% suggests glomerular origin)
   • Look for RBC casts (pathognomonic for glomerular bleeding) 1

Imaging and Specialized Evaluation

For Low-Risk Patients (younger, no risk factors)

• Renal ultrasound (sensitivity 50%, specificity 95%) 1, 3
• Consider foregoing cystoscopy in patients ≤40 years with microscopic hematuria and no risk factors 3

For Intermediate to High-Risk Patients

• CT urography (sensitivity 92%, specificity 93%) 1
• Cystoscopy (essential for detecting bladder pathology)
• For patients with renal insufficiency or contrast allergy: MR urography or ultrasound 1

Important Clinical Considerations

• Voided urinary cytology is no longer recommended in the initial screening protocol for asymptomatic microscopic hematuria due to low sensitivity (37%) 2, 3
• The incidence of urological malignancy in young adults (<40 years) with microscopic hematuria is low, but not zero (reported at 20% in high-grade hematuria) 4
• Patients with microscopic hematuria and loin pain should undergo uretroscopy even with normal radiological findings 4
• Delays >9 months in evaluation of hematuria in patients with bladder cancer are associated with decreased survival 1

Follow-up Recommendations

• If asymptomatic microhematuria (AMH) persists after negative urologic workup, yearly urinalyses should be conducted
• If a patient with persistent AMH has two consecutive negative annual urinalyses, no further evaluation is necessary 1
• For persistent or recurrent AMH after initial negative workup, consider repeat evaluation within 3-5 years 1

Common Pitfalls to Avoid

• Assuming a benign cause without complete evaluation in high-risk patients 1
• Using inadequate imaging (e.g., ultrasound alone) in high-risk patients 1
• Dismissing microscopic hematuria in patients with overactive bladder symptoms 1
• Sex disparities in referral patterns (hematuria should be evaluated regardless of sex) 1
• Failure to recognize that "idiopathic microscopic hematuria" accounts for approximately 80% of patients with asymptomatic hematuria 5

Remember that microscopic hematuria, even when trace, can be a sign of significant urological pathology, particularly in high-risk patients. A systematic approach to evaluation helps ensure that serious conditions are not missed while avoiding unnecessary testing in low-risk individuals.