Proteinuria in Nephritic Syndrome
Nephritic syndrome typically presents with proteinuria in the sub-nephrotic range, generally less than 3.5 g/24 hours (or protein-to-creatinine ratio <3.5 g/g), though the exact amount varies and is not the defining feature of this syndrome. 1
Key Distinguishing Features
The critical distinction between nephritic and nephrotic syndromes lies not in a specific proteinuria threshold, but in the clinical presentation pattern:
Nephritic Syndrome Characteristics
- Proteinuria is present but typically <3.0-3.5 g/24 hours (sub-nephrotic range), accompanied by hematuria, hypertension, and abnormal kidney function 1
- The hallmark is active urinary sediment with hematuria and often red blood cell casts, distinguishing it from nephrotic syndrome 1
- Hypertension is typically present and is a defining feature of the nephritic pattern 1
- Edema may occur but is less severe than in nephrotic syndrome 1
Nephrotic Syndrome for Comparison
- Proteinuria exceeds 3.5 g/24 hours (or PCR >300-350 mg/mmol), with hypoalbuminemia (<3.0 g/dL in adults, ≤2.5 g/dL in children) and edema as the defining triad 2, 3
- In children, nephrotic-range proteinuria is defined as ≥40 mg/h/m² or first morning urine protein-to-creatinine ratio ≥2 g/g 2, 4
Clinical Implications
The amount of proteinuria in nephritic syndrome is variable and less diagnostically important than the constellation of findings: hematuria with dysmorphic red blood cells or casts, acute kidney injury, and hypertension define the syndrome rather than a specific proteinuria cutoff 1.
Common Causes of Nephritic Syndrome
- Post-infectious glomerulonephritis, IgA nephropathy, and lupus nephritis are the predominant causes 1
- These conditions carry a poorer prognosis than typical nephrotic syndrome due to the inflammatory nature and associated kidney function decline 1
Important Caveat
While nephritic syndrome typically has sub-nephrotic proteinuria, overlap syndromes exist where patients may have features of both nephritic and nephrotic presentations, particularly in conditions like lupus nephritis where nephrotic-range proteinuria can coexist with active inflammatory changes 5, 6.