Differentiating Nephrotic from Nephritic Syndrome

Initial Laboratory Assessment

The American College of Radiology recommends urinalysis with microscopic examination to identify the syndrome pattern, looking specifically for red blood cell casts and dysmorphic RBCs indicating glomerular bleeding 1
Quantifying proteinuria using spot urine protein-to-creatinine ratio (PCR) or albumin-to-creatinine ratio (ACR) is essential, with nephrotic range defined as PCR >300-350 mg/mmol or total protein >3.5 g/24 hours 3
Serum albumin measurement is crucial, with hypoalbuminemia (<3.0 g/dL or <30 g/L) defining nephrotic syndrome 4
Serum creatinine with eGFR calculation using CKD-EPI equation assesses renal function, with acute kidney injury more characteristic of nephritic syndrome 1

Heavy proteinuria (>3.5 g/24 hours or PCR >3500 mg/g), hypoalbuminemia (<3.0 g/dL), and peripheral edema form the diagnostic triad of nephrotic syndrome 3

Complement levels (C3, C4) are critical, with decreased C3 suggesting post-infectious glomerulonephritis, lupus nephritis, or membranoproliferative GN (all nephritic patterns) 6
Antinuclear antibodies (ANA) and anti-dsDNA testing excludes systemic lupus erythematosus 6
Hepatitis B and C serology, HIV testing are necessary as secondary causes of both syndromes 6

Renal biopsy is indicated when clinical features suggest nephritic syndrome or diffuse glomerular disease, or when steroid resistance develops after 4 weeks of treatment in presumed minimal change disease 6
Adult patients with nephrotic syndrome require histopathological diagnosis before initiating immunosuppression 6