Does Lupus Nephritis Cause Blood in the Urine?
Yes, lupus nephritis commonly causes hematuria (blood in the urine), which is a key diagnostic finding used to identify kidney involvement in systemic lupus erythematosus patients. 1
Hematuria as a Diagnostic Marker
The KDIGO 2024 guidelines explicitly identify abnormal urine sediment as evidence of lupus nephritis, specifically including: 1
- Acanthocytes (≥5%)
- Red blood cell casts
- White blood cell casts
These urinary findings, along with proteinuria ≥2+ on dipstick, trigger the diagnostic algorithm for lupus nephritis and warrant quantification of proteinuria. 1
Clinical Presentation
Hematuria in lupus nephritis can present in several forms: 2, 3
- Microscopic hematuria (detected only on urinalysis) is common 3
- Glomerular hematuria (new onset) is particularly suggestive of active lupus nephritis 2
- "Dark" urine may be reported by patients with more significant hematuria 4
The presence of hematuria without dysmorphia has been documented in lupus nephritis cases, though dysmorphic red blood cells are more typical of glomerular disease. 5
Importance in Disease Monitoring
Active urinary sediment changes, including hematuria, are major clinical indicators of lupus nephritis activity and flare. 6 The KDIGO guidelines emphasize that patients with SLE should be actively and regularly monitored, as kidney involvement can remain silent or asymptomatic for significant periods despite ongoing inflammation. 1
Critical Caveat
The severity of urinary findings does not always correlate with the extent or severity of kidney involvement. 1 A holistic assessment including clinical, urinary, and laboratory parameters is essential, as severe active nephritis can sometimes present with relatively "insignificant" proteinuria or hematuria. 1 This is why kidney biopsy remains the gold standard for diagnosis and classification of lupus nephritis. 2
Populations at Higher Risk
Maintain a particularly high index of suspicion for hematuria and lupus nephritis in: 1, 7