Nephrotic Syndrome

Basics

Description

  • Diseases causing defect in glomerular filtration barrier, producing proteinuria:
    • Proteinuria >3 g in 24 hr
    • Hypoalbuminemia (serum albumin <3 g/dL)
    • Peripheral edema due to hypoalbuminemia
    • Hypogammaglobulinemia
    • Hyperlipidemia (fasting cholesterol >200 mg/dL)
  • Urine fat (oval fat bodies, fatty/waxy casts)
  • Glomerular basement membrane altered by:
    • Immune complexes
    • Nephrotoxic antibodies
    • Nonimmune mechanisms
    • Result: More permeable glomerular membranes and excretion of albumin and large proteins

Pathophysiology

  • Proteinuria due to increased filtration within renal glomeruli
  • Edema due to sodium retention and hypoalbuminemia
  • Postural hypotension, syncope, and shock due to severe hypoalbuminemia
  • Hyperlipidemia due to hepatic lipoprotein synthesis stimulated by decreased plasma oncotic pressure
  • Cumulative thromboembolism risk increased if:
    • Hypovolemia
    • Low serum albumin
    • High protein excretion
    • High fibrinogen levels
    • Low antithrombin III levels

Etiology

  • Due to primary renal or systemic diseases
  • Membranous nephropathy:
    • Primary cause of nephrotic syndrome in adults
    • Other causes include chronic infection (hepatitis B virus, hepatitis C virus, autoimmune disorders)
    • Renal biopsy shows involvement of all glomeruli
    • Women have better prognosis
    • 30% may slowly progress to renal failure
    • Renal vein thrombosis causes sudden loss of renal function
    • Treat with steroids and cytotoxic agents in severe cases
  • Minimal change disease:
    • Most common cause (90%) of nephrotic syndrome in children
    • Other causes: Idiopathic, NSAIDs, paraneoplastic syndrome associated with malignancy (often Hodgkin lymphoma)
    • Best prognosis among all nephrotic syndromes
    • Good response to steroids
  • Focal segmental glomerulosclerosis (FSGS):
    • Young patients (15–30 yr) with nephrotic syndrome
    • Presents with high BP, renal insufficiency, proteinuria, microscopic or gross hematuria
    • Causes include HIV, heroin abuse, obesity, hematologic malignancies
    • Primary FSGS responds to steroids
    • Secondary FSGS treated with ACE inhibitors (ACEI)
    • Collapsing FSGS usually seen in HIV patients
  • Membranoproliferative glomerulonephritis:
    • May present with nephrotic, nonnephrotic, or nephritic sediment
    • Complement levels are persistently low
    • Supportive care: Steroids may be helpful in children
    • Aspirin and dipyridamole may slow progression
  • Diabetes mellitus/diabetic nephropathy:
    • Most common secondary cause of nephrotic range proteinuria in adults
    • Microalbuminuria (30–300 mg/24 hr) is primary indicator of renal disease
    • Worsening of renal function in 5–7 yr
    • Does not cause rapid decline in renal function
    • Strict control of blood sugar and ACEI therapy slow progression
  • Monoclonal gammopathies:
    • Include amyloidosis, multiple myeloma, and light-chain nephropathy
    • Renal manifestations include proteinuria, nephrotic syndrome, nephritic syndrome, and acute renal failure
    • Lab findings include pseudohyponatremia, low anion gap, hypercalcemia, and Bence Jones proteinuria
    • Congo red stain of amyloid shows apple-green birefringence in polarized light
    • Supportive care: Steroids and melphalan have some benefit
  • Systemic lupus erythematosus (SLE):
    • Can present initially as a nephritic process, with progression to nephrotic syndrome
  • HIV-associated nephropathy:
    • FSGS is most common nephropathy
    • Collapsing glomerulopathy in seropositive HIV carriers with supernephrotic syndrome results in end-stage renal failure that is rapidly progressive (months)
  • Other causes include preeclampsia, hepatitis, and drug reactions (culprits include NSAIDs, gold, penicillamine)

There's more to see -- the rest of this topic is available only to subscribers.