Type 1 Renal Tubular Acidosis

Aka: Type 1 Renal Tubular Acidosis, Type I Renal Tubular Acidosis, Type I RTA, Distal RTA, Distal Renal Tubular Acidosis, Classic RTA

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II. Pathophysiology

  1. Distal Tubule fails to excrete ammonia

III. Causes

  1. Autosomal Dominant inherited disorder
  2. Acquired causes
    1. Systemic Lupus Erythematosus
    2. Sickle Cell Anemia
    3. Nephrocalcinosis related disorders
      1. Hyperparathyroidism
      2. Medullary sponge Kidney
    4. Medications and Toxins
      1. Amphotericin B
      2. Lithium
      3. Toluene

IV. Signs

  1. Musculoskeletal weakness
  2. Recurrent Nephrolithiasis

V. Labs

  1. Arterial Blood Gas (ABG)
    1. Non-Anion Gap Metabolic Acidosis
  2. Urine pH
    1. Elevated >5.5 despite Metabolic Acidosis
  3. Serum Potassium
    1. Low or normal
  4. Fractional Excretion of Bicarbonate
    1. FE-HCO3 <5%: Distal RTA
    2. FE-HCO3 >15%: Proximal RTA
      1. Assumes serum bicarbonate >20 meq/L

VI. Management: Bicarbonate Supplementation

  1. Dose: 1-2 meq/kg/day
  2. Goal: Serum bicarbonate > 22 meq/L
  3. Corrects Hypokalemia

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