Renal Tubular Acidosis (RTA)

Snapshot

  • A 36-year-old woman presents to the emergency department with left-sided back pain that radiates to her left groin. Medical history is significant for Sjogren syndrome. On physical exam there is left-sided costovertebral angle tenderness. Laboratory testing is notable for hyperchloremic and normal anion gap metabolic acidosis and hypokalemia. Non-contrast computerized tomography (CT) of the abdomen demonstrates urolithiasis. She is started on ibuprofen and intravenous fluids. Once the calculi passed it was found to be a calcium phosphate stone. (Type I renal tubular acidosis)

Introduction

  • Clinical definition
    • renal tubular dysfunction that results in a hyperchloremic and normal anion gap metabolic acidosis
      • there is a relatively normal glomerular filtration rate
Renal Tubular Acidosis
TypeEtiologyPathogenesisTreatmentComments
Type II (proximal) Fanconi syndromeCarbonic anhydrase II deficiencyMedicationsacetazolamideifosfamidetopiramateexpired tetracyclinesHeavy metalse.g., mercury, cadmium, copper, and leadMultiple myelomaWilson disease↓ bicarbonate reabsorption in the proximal tubulePotassium citrateThiazide diureticsAssociated with hypokalemiaAt risk of developing hypophosphatemic ricketsUrine pH is initially > 5.5 and then later becomes < 5.5
Type I (distal)Sjogren syndromeRheumatoid arthritisAnion exchanger gene mutationsMedicationslithiumifosfamideanalgesicsamphotericin BDefective hydrogen secretionSodium bicarbonate or sodium citrateAssociated with hypokalemiaAt risk of developing calcium phosphate stonesUrine pH > 5.5
Type IV (hyporeninemic hypoaldosteronism)Diabetic nephropathyMineralocorticoid deficiencySickle cell diseaseSystemic lupus erythematosusMedicationsheparinangiotensin converting enzyme (ACE) inhibitorsangiogensin receptor blockers (ARBs)cyclosporineTMP-SMXpotassium sparing diureticsHyperkalemia results in ↓ ammonia (NH3) synthesis↓ the capacity to carry acidTreatment depends on the underlying causeAssociated with hyperkalemiaUrine pH < 5.5