Type 2 Renal Tubular Acidosis

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

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II. Epidemiology

  1. Most commonly affects children

III. 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

IV. Causes

  1. Medications
    1. Acetazolamide
  2. Fanconi's Syndrome
  3. Medullary cystic disease
  4. Multiple Myeloma
  5. Nephrotic Syndrome
  6. Renal Transplantation

V. Signs (Presentation)

  1. Failure to Thrive
  2. Growth retardation
  3. Vomiting
  4. Dehydration
  5. Lethargy

VI. 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

VII. Radiology: XRay

  1. Children: Rickets
  2. Adults: Osteopenia

VIII. 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

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