Type 1 Distal Renal Tubular Acidosis (RTA)

Etiology

Genetic Disease

  • Carbonic Anhydrase I (CA-I) Deficiency/Alteration
  • Ehlers-Danlos Syndrome (see Ehlers-Danlos Syndrome, [[Ehlers-Danlos Syndrome]])
  • Familial Type 1 Distal Renal Tubular Acidosis
    • Autosomal Dominant
    • Autosomal Recessive
  • Hereditary Elliptocytosis (see Hereditary Elliptocytosis, [[Hereditary Elliptocytosis]])
  • Marfan Syndrome (see Marfan Syndrome, [[Marfan Syndrome]])
  • Medullary Cystic Disease: produces both distal RTA and proximal RTA
  • Neuroaxonal Dystrophy
  • Osteopetrosis
  • Sickle Cell Disease (see Sickle Cell Disease, [[Sickle Cell Disease]])
  • Wilson Disease (see Wilson Disease, [[Wilson Disease]])

Tubulointerstitial Renal Disease

  • Chronic Pyelonephritis
  • Leprosy (see Leprosy, [[Leprosy]])
  • Obstructive Uropathy
  • Renal Transplant Rejection (see Renal Transplant, [[Renal Transplant]])

Nephrocalcinosis Syndromes

Autoimmune Disease

Hypergammaglobulinemic States

  • Amyloidosis (see Amyloidosis, [[Amyloidosis]]): produces both distal RTA and proximal RTA
  • Cryoglobulinemia (see Cryoglobulinemia, [[Cryoglobulinemia]])
  • Multiple Myeloma (see Multiple Myeloma, [[Multiple Myeloma]]): produces both distal RTA and proximal RTA

Drugs/Toxins

  • Amphotericin B (see Amphotericin, [[Amphotericin]])
  • Cyclamate
  • Ifosfamide (Ifex) (see Ifosfamide, [[Ifosfamide]]): produces both distal RTA and proximal RTA
  • Lithium Carbonate (see Lithium, [[Lithium]])
  • Toluene Intoxication (see Toluene, [[Toluene]])

Other

  • Cirrhosis (see End-Stage Liver Disease, [[End-Stage Liver Disease]])
  • Human Immunodeficiency Virus (HIV)/AIDS (see Human Immunodeficiency Virus, [[Human Immunodeficiency Virus]]): possible etiology
  • Idiopathic (Sporadic) Type 1 Distal Renal Tubular Acidosis

Physiology

  • Impaired distal tubular H+ secretion/ excessive back-diffusion of H+ in collecting duct (by intercalated cells)
  • Renal bicarbonate loss: bicarbonate is replaced by chloride (produces hyperchloremia)

Diagnosis

  • Serum Potassium: hypokalemia
  • Urine pH: >5.4
  • Urine AG: (urine Na+ + urine K+) – (urine Cl-)
    • Normal: -20 to -50 mEq/L
    • Positive: due to decreased renal ammonium ion (NH4+) excretion, as NH4Cl
  • NH4Cl Oral Load Test: patient is unable to decrease urine pH <5.4

Clinical Manifestations

Renal Manifestations


Treatment

  • Potassium citrate or potassium bicarbonate: typical requirement is 1-2 mEq/kg/day

References

  • The use of the urinary anion gap in the diagnosis of hyperchloremic metabolic acidosis. N Engl J Med 1988; 318 594-599
  • A modified classification of metabolic acidosis: a pathophysiological approach. Nephron 1992; 60:129-133