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Type 2 Renal Tubular Acidosis

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Type 2 Renal Tubular Acidosis, Type II Renal Tubular Acidosis, Type II RTA, Proximal RTA, Proximal Renal Tubular Acidosis

  • Epidemiology
  1. Most commonly affects children
  • Pathophysiology
  1. Proximal Tubule defect of bicarbonate reabsorption
  2. Results in bicarbonate wasting
    1. Initially distal tubule attempts to reabsorb
    2. Later distal tubule mechanisms overcome
  • Causes
  1. Medications
    1. Acetazolamide
  2. Fanconi's Syndrome
  3. Medullary cystic disease
  4. Multiple Myeloma
  5. Nephrotic Syndrome
  6. Renal Transplantation
  • Signs (Presentation)
  1. Failure to Thrive
  2. Growth retardation
  3. Vomiting
  4. Dehydration
  5. Lethargy
  • Labs
  1. Arterial Blood Gas
    1. Mild to moderate Non-Anion Gap Metabolic Acidosis
  2. Serum bicarbonate decreased
    1. Usually not lower than 15 meq/L
  3. Urine pH
    1. Exceeds 5.5 except in severe Metabolic Acidosis
  4. Fractional Excretion of Bicarbonate
    1. FE-HCO3 exceeds 15% if serum bicarbonate >20 meq/L
    2. FE-HCO3 <5% in Distal RTA
  • Radiology
  • XRay
  1. Children: Rickets
  2. Adults: Osteopenia
  • Management
  1. High dose Bicarbonate Supplementation
    1. Oral Bicarbonate 10-25 meq/kg/day
  2. Observe for Hypokalemia
  3. Treat Osteomalacia in adults
    1. Vitamin D supplementation
    2. Calcium Supplementation
  4. Treat Rickets in children
    1. Vitamin D Supplementation
    2. Sodium phosphate 1.6 grams per day