Management of Asymptomatic Microhematuria with >80% Dysmorphic RBCs
For a 38-year-old man with asymptomatic microhematuria showing >80% dysmorphic RBCs on urine microscopy, referral to a nephrologist for evaluation of glomerular disease is the appropriate next step. 1
Rationale for Nephrology Referral
The presence of highly dysmorphic RBCs (>80%) strongly suggests glomerular origin of the hematuria. According to the American Urological Association guidelines, patients with microscopic hematuria who have findings suggestive of potential nephrologic disorders, such as highly dysmorphic RBCs (>80%), should be referred to nephrology for evaluation and treatment 1.
Dysmorphic urinary red blood cells show variation in size and shape with irregular or distorted outlines, indicating glomerular bleeding. When more than 80% of RBCs are dysmorphic, this is highly suggestive of glomerular disease rather than lower urinary tract bleeding 2.
Pre-Nephrology Evaluation
Before the nephrology visit, the following tests should be ordered:
- Serum creatinine and BUN to assess renal function
- Complete blood count
- 24-hour urine collection to quantify protein excretion
- Blood pressure measurement
The presence of significant proteinuria (>500-1000 mg/24 hours) would further support glomerular disease 2, 1.
Importance of Complete Evaluation
While nephrology referral is the primary next step, it's important to note that:
The predominance of dysmorphic RBCs does not completely exclude urological disease. Research shows that among patients with ≥40% dysmorphic RBCs, 34% still had urological diseases, including 27.3% with clinically meaningful malignancies 3.
For predicting glomerular disease, the presence of proteinuria demonstrates higher diagnostic value than dysmorphic RBCs alone 3.
Potential Pitfalls to Avoid
Don't assume urological evaluation is unnecessary: While nephrology evaluation is the priority next step, completely omitting urological evaluation may lead to missed diagnoses. Consider urological evaluation after nephrology assessment if glomerular disease is not confirmed or if there are other risk factors for urological disease.
Don't overlook additional testing: The presence of red cell casts, significant proteinuria, or elevated creatinine levels would further support glomerular disease and should be assessed 4.
Don't delay nephrology referral: A single positive result of >80% dysmorphic RBCs is sufficient to proceed with nephrology evaluation, and repeat microscopic analysis is not necessary 1.
Follow-up Considerations
After nephrology evaluation, the nephrologist may recommend:
- Renal biopsy to determine the specific glomerular disease
- Additional specialized testing
- Treatment based on the underlying glomerular pathology
If glomerular disease is ruled out by the nephrologist, consider urological evaluation with:
- Cystoscopy
- Appropriate imaging (CT urography or renal ultrasound based on risk factors)
This approach ensures comprehensive evaluation of both potential glomerular and urological causes of the patient's microhematuria.