Acute Nephritic Syndrome and APSGN

Acute Nephritic Syndrome (APSGN)

• Presents with edema, hematuria, and hypertension with or without oliguria
• 95% of clinical cases have at least 2 manifestations, and 40% have the full-blown acute nephritic syndrome
• Laboratory studies:
  • Evidence of preceding streptococcal infection
  • Antibody titers to extracellular products of streptococci are positive in more than 95% of patients with pharyngitis and 80% of patients with skin infections
  • Elevated BUN and creatinine values
  • Low serum complement levels
• Urinalysis:
  • Results are always abnormal
• Imaging studies:
  • Chest radiographs may show findings of congestive heart failure
  • Atypical features in the early phase that suggest the need for renal biopsy include:
    • No rise in antistreptococcal antibodies
    • Absence of the latent period
    • Normal serum complement levels
    • Anuria
    • Massive proteinuria in the acute stage
    • Rapidly deteriorating renal function
• Complications:
  • Acute phase:
    • Congestive heart failure
    • Azotemia
    • Early death secondary to congestive heart failure and azotemia
  • Chronic phase:
    • Nephrotic-range proteinuria
    • Chronic renal insufficiency and end-stage renal disease
• Management:
  • Medical care:
    • Symptomatic therapy
    • Restrict salt and water
    • Control edema and blood pressure
    • Treat hypertension with calcium channel blockers or angiotensin-converting enzyme inhibitors
    • Indications for dialysis include life-threatening hyperkalemia and clinical manifestations of uremia
  • Specific therapy for streptococcal infection
  • Treat patients, family members, and close personal contacts who are infected

Nephrotic Syndrome (NS)

• Definition:
  • Massive proteinuria
  • Hypoalbuminemia
  • Decreased plasma oncotic pressure
  • Transudation of fluid into interstitium
• Etiology:
  • Primary (disease specific to the kidneys):
    • Minimal-change nephropathy
    • Focal glomerulosclerosis
    • Membranous nephropathy
    • Hereditary nephropathies
  • Secondary (renal manifestation of a systemic general illness):
    • Metabolic (e.g. amyloidosis, diabetes mellitus)
    • Immunologic (e.g. Henoch-Schönlein purpura, SLE)
    • Drug-related (e.g. interferon alfa, NSAIDs)
    • Neoplastic (e.g. leukemia, lymphomas)
    • Allergic (e.g. antitoxins, insect stings, snake venoms)
    • Bacterial (e.g. infective endocarditis)
    • Viral (e.g. Epstein-Barr virus infection, hepatitis B and C)
• Clinical manifestations:
  • Edema is the presenting symptom in about 95% of children
  • Anorexia, irritability, fatigue, abdominal discomfort, and diarrhea
  • Respiratory distress
  • Gross hematuria
  • Hypertension
• Laboratory investigations:
  • Confirm nephrotic-range proteinuria
  • Confirm hypoalbuminemia
  • Confirm hyperlipidemia
• Treatment:
  • Steroids (prednisone)
  • Steroid-sparing agents (e.g. cyclosporin A)
  • Alkylating agents (e.g. cyclophosphamide)
  • Calcineurin inhibitors (e.g. cyclosporin A)
  • ACE inhibitor
  • Diuretic therapy (e.g. furosemide)

Frequently Relapsing, Steroid-Dependent, and Steroid-Resistant Disease

• Frequently-relapsing nephrotic syndrome (FRNS):
  • Defined as steroid-sensitive nephrotic syndrome with 2 or more relapses within 6 months or three times or more within 1 year
  • Treatment: prednisone, steroid-sparing agents, and tapering over 3 or more months
• Steroid-dependent nephrotic syndrome (SDNS):
  • Defined as steroid-sensitive nephrotic syndrome with 2 or more consecutive relapses during tapering or within 14 days of stopping steroids
  • Treatment: prednisone, steroid-sparing agents, and tapering over 3 or more months
• Steroid-resistant nephrotic syndrome (SRNS):
  • Defined as children who continue to have proteinuria after 8 weeks of steroid therapy
  • Treatment: cyclosporin A, alkylating agents, and calcineurin inhibitors