In an adult or adolescent presenting with new‑onset hematuria, proteinuria, edema, hypertension, or recent infection, which urine tests should be ordered to evaluate for glomerulonephritis?

Urine Tests to Evaluate for Glomerulonephritis

Order urinalysis with microscopic examination of the sediment, spot urine protein-to-creatinine ratio, and serum creatinine immediately—these three tests form the essential initial workup to distinguish glomerular from non-glomerular causes of hematuria and guide urgent nephrology referral. 1, 2, 3

Essential Initial Urine Tests

1. Urinalysis with Microscopic Sediment Examination

This is the single most important test—never rely on dipstick alone. 1, 2

• Confirm true hematuria: Verify ≥3 red blood cells per high-power field (RBC/HPF) on microscopic examination of a properly collected clean-catch midstream specimen 1, 2
• Assess RBC morphology: Look for dysmorphic RBCs, which indicate glomerular bleeding 4, 1, 2
  • >80% dysmorphic RBCs strongly suggests glomerular disease (some guidelines use >50% as threshold) 1, 2, 5
  • Acanthocytes (ring-shaped RBCs with protruding blebs) are particularly specific for glomerular injury 5
• Search for red blood cell casts: These are pathognomonic for glomerulonephritis—their presence confirms active glomerular inflammation 4, 1, 2, 5
• Note urine color: Tea-colored or cola-colored urine suggests glomerular bleeding and mandates urgent evaluation 4, 1, 2

2. Quantitative Proteinuria Assessment

• Order spot urine protein-to-creatinine ratio rather than relying on dipstick, which is unreliable for accurate quantification 1, 2, 3
• Significant proteinuria is defined as:
  • Protein-to-creatinine ratio >0.2 g/g (or >200 mg/g) 1, 2
  • Values >0.5 g/g (≈500 mg/24 hours) strongly suggest renal parenchymal disease 1, 3
  • Values >1.0 g/g warrant immediate nephrology referral 1
• The combination of proteinuria + hematuria strongly indicates glomerular disease, especially when dysmorphic RBCs or casts are present 4, 1, 2, 3

3. Serum Creatinine and Renal Function

• Measure serum creatinine immediately to assess for acute kidney injury 4, 1, 3
• Elevated creatinine with hematuria and proteinuria signals acute glomerulonephritis and requires urgent nephrology consultation 1, 3, 6
• Obtain complete metabolic panel including BUN, electrolytes, and albumin 4, 1

Algorithmic Approach to Test Interpretation

Step 1: Confirm True Hematuria

• Microscopic examination showing ≥3 RBCs/HPF on at least two of three properly collected specimens 1, 2
• Dipstick has only 65-99% specificity and produces false positives from myoglobin, hemoglobin, or menstrual contamination 1, 2

Step 2: Determine Glomerular vs. Non-Glomerular Source

Glomerular indicators (refer to nephrology): 1, 2, 3

• >80% dysmorphic RBCs or presence of red cell casts
• Protein-to-creatinine ratio >0.5 g/g
• Elevated serum creatinine or declining renal function
• Tea-colored urine
• Hypertension accompanying hematuria and proteinuria

Non-glomerular indicators (complete urologic evaluation): 1, 3

• 80% normal-shaped RBCs

• Minimal proteinuria (<0.2 g/g)
• Normal serum creatinine
• Bright red blood

Step 3: Additional Serologic Testing (if glomerular source suspected)

• Complement levels (C3, C4): Low levels suggest post-infectious glomerulonephritis, lupus nephritis, or C3 glomerulopathy 1, 6
• Antinuclear antibody (ANA) and anti-dsDNA: Positive in lupus nephritis 1, 6
• ANCA (PR3 and MPO): Positive in ANCA-associated vasculitis 1, 6
• Anti-GBM antibodies: If rapidly progressive glomerulonephritis suspected 6

Immediate Nephrology Referral Criteria

Refer urgently to nephrology when ANY of the following are present: 1, 2, 3

• Red blood cell casts on microscopy
• >80% dysmorphic RBCs
• Protein-to-creatinine ratio >0.5 g/g (especially if persistent or rising)
• Elevated serum creatinine or declining eGFR
• Hypertension with hematuria and proteinuria
• Rapidly progressive clinical course (rising creatinine over days to weeks)

Critical Pitfalls to Avoid

• Never attribute hematuria to anticoagulation or antiplatelet therapy—these medications unmask underlying pathology but do not cause hematuria 1, 2
• Do not skip microscopic examination—dipstick positivity must be confirmed with ≥3 RBCs/HPF before initiating workup 1, 2
• Do not ignore glomerular features even in older patients—malignancy can coexist with glomerular disease, so both urologic and nephrologic evaluations may be needed 1
• Do not delay nephrology referral if red cell casts or predominantly dysmorphic RBCs are present—these indicate active glomerulonephritis requiring prompt intervention 1, 2, 5, 6

Special Considerations

In Children

• Renal ultrasound is appropriate first-line imaging to assess kidney anatomy before potential biopsy 4, 1
• Children with isolated microscopic hematuria without proteinuria or dysmorphic RBCs do not require imaging initially 4, 1
• Post-infectious glomerulonephritis is the most common acute glomerulonephritis in children, typically following streptococcal infection 4, 7

Clinical Presentations of Glomerulonephritis

• Acute nephritic syndrome: Abrupt onset of hematuria, edema, hypertension, and reduced renal function 6, 8, 7
• Rapidly progressive glomerulonephritis: Rapid decline in kidney function over days to weeks, often with crescents on biopsy 6, 7, 9
• Asymptomatic hematuria with proteinuria: Most common presentation, may represent IgA nephropathy or other chronic glomerular diseases 6, 8