Dysmorphic RBCs in Urinalysis

🎯 Why Dysmorphic RBCs Matter

Dysmorphic RBCs—especially acanthocytes—indicate glomerular bleeding and help distinguish glomerulonephritis from urologic sources (stones, tumors, infection). Glomerular patterns warrant expedited workup and often nephrology consultation.

Teaching Pearl: RBC casts are pathognomonic but uncommon; dysmorphic RBCs are more sensitive and practical to detect.

📋 Definitions & Thresholds

Dysmorphic RBC	Misshapen erythrocyte from glomerular passage; spicules/blebs common
Acanthocyte (G1 cell)	Ring form with vesicle-like blebs—highly specific for glomerular origin
>5% Dysmorphic	Suggests glomerular source
>20% Acanthocytes	Highly specific for glomerulonephritis

🔬 Optimal Technique

Fresh Specimen: Midstream, clean-catch within 2 hours

Phase-Contrast: Preferred; bright-field acceptable with training

Scanning: Low power for casts, high power for morphology

Tip: If unavailable, partner with a lab using phase-contrast or send to a nephrology microscopy service.

📊 Test Characteristics

Specificity: Acanthocytes are highly specific; dysmorphia alone less so

Sensitivity: Improves with fresh samples and phase-contrast technique

Pitfalls: Prolonged storage, high osmolality, and severe hematuria can distort RBCs

⚠️ Common Errors to Avoid

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Over-calling dysmorphia in old specimens

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Misreading crenated cells (hypertonic urine) as dysmorphic

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Diagnosing after vigorous exercise (transient changes)

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Using standard bright-field without proper training

🚨 When to Escalate

→ Urgent Nephrology Consult

Dysmorphic RBCs or RBC casts + AKI/proteinuria

→ Expedite Serologies

Complements, ANCA, anti-GBM if GN suspected

→ Consider Urology

Gross hematuria with clots or terminal stream bleeding

🔗 Clinical Integration

Proteinuria + Dysmorphic RBCs

Strengthens GN likelihood—check UPCR

Hypertension/Edema

Supports nephritic syndrome pattern

Normal Complements

Narrows differential (IgA, ANCA, anti-GBM)

Case Tie-in: See Case 22 (RPGN with IgA vasculitis) for real-world application.

📚 References & Further Reading

KDIGO Glomerular Diseases guideline framework • Microscopy best-practice reviews • Studies validating acanthocyte thresholds for glomerular hematuria • Educational atlases of urinary sediment morphology (phase-contrast)

🔬 UA Overview 🧫 RBC Morphology 🔎 Ancillary Testing 📚 Interpretation

🔬 Dysmorphic RBCs in Urinalysis