## Distinguishing IgA Nephropathy from Diabetic Nephropathy **Key Point:** IgA nephropathy (primary glomerulonephritis) and diabetic nephropathy (secondary glomerulosclerosis) can both present with proteinuria, hypertension, and reduced eGFR, but urinalysis findings are the most specific discriminator. ### Comparison Table | Feature | IgA Nephropathy | Diabetic Nephropathy | |---------|-----------------|---------------------| | **Hematuria** | **Present (often gross or microscopic with dysmorphic RBCs)** | **Absent or minimal (non-dysmorphic)** | | **Proteinuria pattern** | Variable, can be nephrotic or subnephrotic | Progressive, usually non-nephrotic initially | | **Retinopathy** | Absent | Present (almost always if albuminuria) | | **Kidney size** | Normal or near-normal | Enlarged (due to glomerular hyperfiltration) | | **Serum phosphate** | Normal initially | Elevated (late CKD) | | **Kidney biopsy** | IgA deposits on immunofluorescence | Nodular glomerulosclerosis (Kimmelstiel-Wilson) | **High-Yield:** Hematuria with dysmorphic RBCs and RBC casts is a hallmark of glomerulonephritis (including IgA nephropathy) and is **absent in diabetic nephropathy**. This is the single most discriminating urinalysis finding. **Clinical Pearl:** IgA nephropathy is the most common primary glomerulonephritis worldwide. It often presents with episodic gross hematuria (especially after upper respiratory infection) or persistent microscopic hematuria with dysmorphic RBCs — findings that should prompt kidney biopsy and exclude diabetes as the sole cause. **Mnemonic:** **HEMATURIA in GN** — Hematuria (especially dysmorphic) is a **red flag** for primary glomerulonephritis, not diabetic disease. Diabetics with nephropathy have **bland urine** (no RBCs, no casts, just proteinuria). 
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