What is the next step in evaluating a 38-year-old man with microscopic hematuria and dysmorphic Red Blood Cells (RBCs)?

Management of Microscopic Hematuria with Dysmorphic RBCs

The next step in evaluating a 38-year-old man with microscopic hematuria and >80% dysmorphic RBCs should be nephrology referral (option C).

Rationale for Nephrology Referral

The presence of dysmorphic RBCs in this patient's urinalysis is highly suggestive of glomerular disease, which requires nephrology evaluation. According to the American Academy of Family Physicians guidelines, nephrology referral should be considered when there is evidence of dysmorphic red blood cells, which is precisely what we see in this case 1.

The key findings that point to glomerular origin of bleeding include:

• Moderate blood on dipstick with 10-15 RBC/hpf on microscopy

• 80% dysmorphic RBCs, which strongly indicates glomerular pathology

Evaluation Algorithm for Microscopic Hematuria

1. Initial Assessment: This patient has confirmed microscopic hematuria (>3 RBC/hpf)

2. Determine Source of Bleeding:

   • Dysmorphic RBCs >80% strongly suggests glomerular origin
   • According to guidelines, dysmorphic RBCs are indicative of glomerular disease 2, 1

3. Risk Assessment:

   • At 38 years old, the patient is younger than the high-risk threshold for urologic malignancy
   • The predominance of dysmorphic RBCs (>80%) strongly suggests a nephrologic rather than urologic cause

Why Other Options Are Not Appropriate

• Urine cytology (A): Not indicated as first step when dysmorphic RBCs suggest glomerular disease. The AUA no longer recommends routine urine cytology in the initial evaluation of asymptomatic microscopic hematuria 3.

• Repeat microscopic urinalysis (B): Unnecessary since the current urinalysis already shows definitive findings of dysmorphic RBCs.

• CT urogram (D): While CT urography is the preferred imaging for upper tract evaluation in microscopic hematuria, it's not the next step when glomerular disease is strongly suspected based on dysmorphic RBCs 1.

• Cystourethroscopy (E): Primarily evaluates the lower urinary tract for urologic causes. With >80% dysmorphic RBCs, a glomerular cause is much more likely than a urologic cause 1, 4.

Important Considerations

While dysmorphic RBCs strongly suggest glomerular disease, it's worth noting that research has shown that urologic disease cannot be completely excluded based solely on the presence of dysmorphic RBCs. A study found that among patients with ≥40% dysmorphic RBCs, 34% still had urologic diseases, including some with malignancies 4. However, with >80% dysmorphic RBCs in this case, the likelihood of glomerular disease is substantially higher.

The nephrology evaluation will likely include:

• Assessment of proteinuria
• Evaluation of renal function
• Consideration of renal biopsy if indicated
• Specific testing for glomerulonephritis and other glomerular diseases

Pitfalls to Avoid

1. Don't assume urologic evaluation is unnecessary: After nephrology assessment, this patient may still need urologic evaluation if glomerular disease is ruled out or if symptoms persist.

2. Don't delay nephrology referral: When dysmorphic RBCs are present in high percentages (>80%), prompt nephrology evaluation is essential to diagnose and treat potential glomerular disease.

3. Don't attribute hematuria to benign causes without proper evaluation: Even with dysmorphic RBCs suggesting glomerular disease, a thorough evaluation is necessary to establish a definitive diagnosis.