From the Guidelines
The next step in evaluating a 38-year-old man with microscopic hematuria and dysmorphic RBCs should be a comprehensive nephrology workup, including a 24-hour urine collection for protein quantification and a renal biopsy, as the presence of dysmorphic RBCs strongly suggests glomerular pathology, which requires prompt investigation 1. The presence of dysmorphic RBCs in the urine is a significant finding that indicates damage to the glomerular filtration barrier, suggesting conditions like IgA nephropathy, lupus nephritis, or rapidly progressive glomerulonephritis, which require specific treatment approaches based on the underlying diagnosis established by renal biopsy.
- Additional testing should include:
- Serum creatinine, blood urea nitrogen (BUN), estimated glomerular filtration rate (eGFR)
- Complete blood count
- Serum complement levels (C3, C4)
- Antinuclear antibody (ANA)
- Anti-neutrophil cytoplasmic antibodies (ANCA)
- Anti-glomerular basement membrane antibodies
- Serology for hepatitis B and C
- Renal ultrasound should be performed to assess kidney size, structure, and rule out obstruction or masses.
- While awaiting nephrology consultation, blood pressure should be carefully monitored and controlled if elevated, typically using an ACE inhibitor like lisinopril 10-20 mg daily or an ARB such as losartan 50-100 mg daily, as these medications not only control hypertension but also provide renoprotection 1. The most recent and highest quality study, published in 2020, recommends a risk classification system for patients with microhematuria, stratified as low-, intermediate-, or high-risk for genitourinary malignancy, and suggests diagnostic evaluation with cystoscopy and upper tract imaging according to patient risk and involving shared decision-making 1.
- Key points to consider:
- The presence of significant proteinuria, red cell casts or renal insufficiency or a predominance of dysmorphic red blood cells in the urine should prompt an evaluation for renal parenchymal disease 1.
- Patients with microscopic hematuria, a negative initial urologic evaluation and no evidence of glomerular bleeding are considered to have isolated hematuria, and the role of renal biopsy in this setting has not been defined 1.
From the Research
Evaluation of Microscopic Hematuria
The patient presents with microscopic hematuria, defined as 10-15 RBCs/hpf with >80% of the cells appearing dysmorphic. The next step in evaluation is crucial for determining the underlying cause of hematuria.
Diagnostic Approach
- The presence of dysmorphic RBCs suggests a glomerular source of bleeding, but it does not preclude urological disease 2.
- Urine cytology can be useful in diagnosing urinary neoplasms, but its role in evaluating microhematuria is debatable 3.
- Refined microscopic urinalysis for RBC morphology has been evaluated in children and adults with known sources of hematuria, but its clinical usefulness in a pediatric population with unknown sources of hematuria is limited 4.
- The American Urological Association guideline recommends further urological evaluation, even in the presence of dysmorphic RBCs 2.
Next Steps
- Considering the patient's presentation, the next step could be to repeat the microscopic urinalysis to confirm the findings and assess for any changes in RBC morphology.
- Alternatively, a nephrology referral may be considered, given the high percentage of dysmorphic RBCs, which suggests a possible glomerular source of bleeding.
- However, urological evaluation, including cystoscopy and CT imaging, should not be omitted, as treatment-requiring urological diseases may be present, even with a high percentage of dysmorphic RBCs 2.
Considerations
- The presence of proteinuria may be a more indicative factor of glomerular disease than the percentage of dysmorphic RBCs 2.
- The diagnostic value of dysmorphic RBCs in identifying glomerular disease is modest, and concomitant presence of proteinuria is more indicative of glomerular origin in patients presenting with microscopic hematuria 2.