From the Guidelines
To diagnose melanoma-associated glomerulonephritis, I strongly recommend ordering a renal biopsy as the gold standard for diagnosis, as stated in the 2021 KDIGO clinical practice guideline for the management of glomerular diseases 1. This is because a renal biopsy provides essential information for definitive diagnosis, including immune complex deposition and characteristic histopathological changes. The following tests should also be considered:
- Urinalysis with microscopy
- 24-hour urine protein collection
- Serum creatinine
- Blood urea nitrogen (BUN)
- Complete blood count (CBC)
- Renal ultrasound
- Specific immunological tests, such as:
- Anti-glomerular basement membrane (anti-GBM) antibodies
- Antinuclear antibodies (ANA)
- Anti-neutrophil cytoplasmic antibodies (ANCA)
- Complement levels (C3, C4)
- Serum protein electrophoresis It is crucial to evaluate melanoma patients with new-onset proteinuria, hematuria, or declining renal function promptly, as glomerulonephritis can be paraneoplastic or related to immune checkpoint inhibitor therapy 1. For patients on immunotherapy, documenting the timing of symptom onset relative to treatment is essential, as treatment approaches differ based on whether the glomerulonephritis is paraneoplastic (requiring cancer treatment) or medication-induced (potentially requiring immunosuppression and drug discontinuation). Early diagnosis is vital, and a renal biopsy is the most reliable method for achieving this, as emphasized by the KDIGO guideline 1.
From the Research
Diagnosis of Melanoma-Associated Glomerulonephritis
To diagnose melanoma-associated glomerulonephritis, the following tests can be ordered:
- Urinalysis to check for proteinuria or hematuria 2, 3
- Serum creatinine to estimate glomerular filtration rate (eGFR) 2, 3
- Blood pressure measurement to assess for hypertension 2
- Renal biopsy for definitive diagnosis 4, 5
- Serologic testing to refine the differential diagnosis 4
Additional Tests
Additional tests that may be ordered include:
- Measurement of blood urea nitrogen (BUN) 5, 3
- Electrolyte panel to assess for electrolyte abnormalities 3
- 24-hour urine collection to measure creatinine clearance 6
- Calculation of renal function using Cockcroft-Gault or abbreviated Modification of Diet in Renal Disease (aMDRD) equations 6
Importance of Monitoring Renal Function
Monitoring renal function is crucial in patients with cancer, including those with melanoma-associated glomerulonephritis, to ensure safe administration of therapeutic agents and to detect any potential renal impairment 3, 6