In lupus nephritis, which of the following urinalysis findings is false: Haematuria (blood in urine) or Proteinuria (excess protein in urine)?

Urinalysis Findings in Lupus Nephritis

Neither hematuria nor proteinuria is false in lupus nephritis - both are common and important urinary findings that indicate kidney involvement in SLE patients.

Diagnostic Urinalysis Findings in Lupus Nephritis

Urinalysis plays a crucial role in diagnosing and monitoring lupus nephritis. According to the 2024 KDIGO guidelines, the following urinary findings are characteristic of lupus nephritis:

Key Urinary Findings:

• Proteinuria: Typically assessed by dipstick protein ≥2+ or quantified as >500 mg/24h 1
• Hematuria: Presence of red blood cells in urine, particularly glomerular hematuria with acanthocytes (≥5%) 1, 2
• Cellular casts: Red blood cell casts and white blood cell casts 1, 2
• Pyuria: Sterile pyuria (>5 white blood cells per high power field) in the absence of infection 3, 4

Clinical Significance of Urinary Findings

Proteinuria

• Serves as a primary marker of glomerular damage in lupus nephritis
• Can range from mild (<500 mg/24h) to nephrotic range (>3.5g/24h)
• The severity can vary considerably in active nephritis and may sometimes appear relatively "insignificant" 1
• Even low-level proteinuria (<1000 mg/24h) can indicate significant lupus nephritis requiring treatment 5

Hematuria

• Indicates active glomerular inflammation
• Often accompanies proteinuria but can occur in isolation
• Isolated hematuria (>5 RBC/HPF) is associated with active renal and non-renal disease activity in 77% of cases 3
• Presence of dysmorphic RBCs or RBC casts strongly suggests glomerular origin

Diagnostic Approach

The KDIGO guidelines recommend the following approach when lupus nephritis is suspected 1, 2:

1. Initial screening: Look for abnormal proteinuria (dipstick ≥2+) and/or active urinary sediment (acanthocytes, RBC casts, WBC casts)
2. Quantification: If proteinuria is present, quantify with urine protein-to-creatinine ratio (UPCR) or 24-hour collection
3. Kidney function assessment: Evaluate serum creatinine and eGFR
4. Kidney biopsy: Indicated when there is:
   • Persistent proteinuria ≥0.5 g/24h (EULAR/ERA-EDTA guidelines) 1
   • Unexplained decrease in GFR
   • Active urinary sediment

Important Clinical Considerations

Pitfalls to Avoid:

• Underestimating mild proteinuria: Even low-level proteinuria (<1000 mg/24h) may represent significant lupus nephritis 6, 5
• Ignoring isolated hematuria or pyuria: These can be manifestations of active lupus nephritis even without proteinuria 3, 4
• Delaying kidney biopsy: Clinical findings don't always correlate with histological severity 1, 2

Monitoring Recommendations:

• Regular urinalysis and UPCR at each visit
• Serum creatinine and eGFR monitoring
• Anti-dsDNA antibodies and complement levels
• Blood pressure control

Treatment Implications

Urinalysis findings guide treatment decisions:

• Class III or IV LN (with or without Class V): MMF or cyclophosphamide plus glucocorticoids 1, 2
• Pure Class V LN: MMF plus glucocorticoids for nephrotic-range proteinuria 1, 2
• All patients should receive hydroxychloroquine unless contraindicated 1

Regular monitoring of urinalysis parameters is essential to assess treatment response, with complete response defined as proteinuria <0.5-0.7 g/24h with normal or near-normal GFR by 12 months 2.