What is the next step in evaluating a 38-year-old man with microscopic hematuria and greater than 80% dysmorphic Red Blood Cells (RBCs) per high-power field?

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 highly dysmorphic RBCs (>80%) strongly suggests glomerular disease as the source of bleeding. According to the American Urological Association (AUA) guidelines, patients with microscopic hematuria who have findings suggestive of potential nephrologic disorders should be referred to nephrology 1.

The 2025 clinical guidelines specifically state that "patients with significant proteinuria and hematuria should be evaluated by a nephrologist to determine the best course of treatment" 2. Dysmorphic RBCs are a key indicator of glomerular origin bleeding, and when present in high percentages (>80% in this case), they warrant nephrologic evaluation.

Why Other Options Are Less Appropriate

• Urine cytology (A): No longer recommended as part of the routine evaluation of asymptomatic microscopic hematuria according to current guidelines 2, 3. The AUA specifically notes that "routine cytologic evaluation of urine is no longer recommended in the initial AMH evaluation" 1.

• Repeat microscopic analysis (B): Not necessary in this case as the finding of >80% dysmorphic RBCs is already highly suggestive of glomerular disease. The current AUA guideline suggests proceeding with evaluation based on a single positive result 1.

• CT urogram (D) and Cystourethroscopy (E): These are primarily indicated for evaluating urologic causes of hematuria. While these may eventually be needed, nephrology consultation should come first when glomerular disease is strongly suspected based on the high percentage of dysmorphic RBCs.

Importance of Dysmorphic RBCs

Dysmorphic RBCs are strongly associated with glomerular disease:

• Studies have shown that when dysmorphic RBCs account for >75% of urinary RBCs, this is highly specific for renal (particularly glomerular) sources of bleeding 4.

• The presence of dysmorphic RBCs has a high specificity (96.3%) for glomerular disease, though sensitivity is lower (20.4%) 5.

Clinical Approach Algorithm

1. Initial assessment: Microscopic hematuria with >80% dysmorphic RBCs strongly suggests glomerular disease

2. First step: Nephrology referral for specialized evaluation of likely glomerular pathology

3. Additional testing that may be ordered by nephrology:

   • Quantification of proteinuria (24-hour collection)
   • Serum creatinine and BUN
   • Immunologic studies
   • Possible renal biopsy

4. Subsequent urologic evaluation may still be considered after nephrology assessment, particularly if:

   • Patient has additional risk factors for urologic malignancy
   • Glomerular disease is ruled out or doesn't fully explain the hematuria

Important Caveat

It's worth noting that even with high percentages of dysmorphic RBCs, urologic disease cannot be completely excluded. Research has shown that among patients with ≥40% dysmorphic RBCs, 34% still had urologic disease, including 27.3% with clinically meaningful malignancies 6. Therefore, after nephrology evaluation, urologic assessment may still be warranted depending on risk factors and nephrology findings.

However, the initial step should be nephrology referral given the strong indication of glomerular pathology based on the high percentage of dysmorphic RBCs.