Definition of Nephrotic Syndrome:

Proteinuria > 3.5 g/24 hours (spot urine/creatinine >3.5 mg/mg)
Hypoalbuminemia
Clinical evidence of edema
Hyperlipidemia
Lipiduria (maltese cross)

Nephrotic Range Proteinuria: > 3 g/24 hours without other findings

Primary Renal:
Minimal Change Disease
Focal Segmental Glomerulosclerosis
Membranous Nephropathy
Fibrillary/Immunotactoid Glomulonephritis

Secondary (Systemic) Disease:
Diabetes
Amyloid
HIV
Drug Induced
Malignancies
Others

Minimal Change Disease:
Epidemiology: most common cause of NS in children < 10 years old; can be primary or secondary
Clinical Presentation: Sudden onset of edema Thrombotic episodes more common in adults AKI may be seen in 20% at time of presentation
Diagnostic Evaluation: Presence of nephrotic syndrome on labs Renal biopsy required for diagnosis
*Remember it appears essentially normal on light microscopy – need electron microscopy.

Focal Segmental Glomerulosclerosis (FSGS)
Epidemiology: most common cause of idiopathic NS in adults, predilection for blacks, can be primary, familial, or secondary (HIV)
Clinical Presentation:
Asymptomatic proteinuria to NS
Hypertension usually seen in 30-50%
Microscopic hematuria 25-75%
Decreased GFR at presentation 20-30%
Diagnostic Evaluation:
Serologic studies negative
Renal biopsy required for diagnosis

* Remember light microscopy shows scarring/sclerosis involving some (focal) glomeruli, which are affected only in a portion of the glomerular capillary bundle (segmental)

Membranous Nephropathy (MN)
Epidemiology: second leading cause of primary nephrotic syndrome; predilection for > 50 years old; can be primary (immune complex disease) or secondary (infection, autoimmune, cancer, drugs)
Clinical Presentation:
Abrupt onset of nephrotic syndrome
50% may have microscopic hematuria
70% have normal BP and GFR at presentation
Thombotic disease more common – especially with low albumin
Diagnostic Evaluation:
Renal biopsy required for diagnosis

* Immunofluorescence microscopy reveals diffuse, granular IgG deposition along capillary walls.

Treatment – General Approach:
Proteinuria:
ACEi/ARB à reduce glomerular pressure à reduce protein excretion (independent of BP effects)
BP Control:
Goal <130/80, reduces proteinuria
Dietary sodium restriction (<2g/day)
Diuretics – usually loop diuretics:
Diuretic resistance due to low albumin / proteinuria
Reduce edema slowly to avoid acute hypovolemia
Hyperlipidemia:
Typically reverse with resolution of disease, dietary modification not helpful
Treat with stains

Funny Cartoon to help you remember the difference between Nephritic and Nephrotic Syndrome