Acute Nephritic Syndrome and APSGN

Study Notes

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