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Renal Tubular Acidosis (RTA)

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Topic updated on 04/26/16 2:13pm

Snapshot
  • On routine lab work of a patient on the inpatient medicine service in the hospital, you notice a metabolic acidosis with a normal anion gap. Further labwork and history is obtained (different scenarios presented below).
    • High urine pH with a low serum potassium (Type I)
    • Low urine pH with a low serum potassium (Type II)
    • The patient is a diabetic with a low urine pH and a high serum potassium (Type IV)
Overview
 
 
Type I (Distal)
Type II (Proximal)
Type 4 (Distal)
Defect
  • H+ secretion in the distal tubule
  • HCO
    3
    reabsorption in the PCT
  • Inadequate aldosterone response impairs distal Na+ reabsorption and K+ secretion
  • It is the most common type of RTA
Urine pH
  • > 5.5
  • < 5.5
  • < 5.5
Serum values
  • Hypokalemia
  • Hypokalemia
  • Hyperkalemia and hyperchoremia
Etiologies
  • Hereditary
  • Amphotericin
  • Collagen vascular disease
  • Cirrhosis
  • Nephrocalcinosis
  • Hereditary
  • Sulfonamides
  • Carbonic anhydrase inhibitors
  • Fanconi syndrome
  • Hyporeninemic hypoaldosteronism
  • HTN
  • DM
  • Chronic interstitial nephritis
  • Sldosterone resistance
Treatment
  • HCO
    3
    with K+
  • HCO
    3
    , K+, thiazides
  • Fludrocortisone, K+ restriction, HCO
    3
 
Introduction
  • A net decrease in tubular hydrogen secretion or bicarbonate reabsorption
  • Produces a non-ion gap acidosis
  • There are three main types
    • type I - distal RTA H+ secretion defect
      • important findings
        • urine pH high
        • serum K low
        • renal stones present
      • diagnostic test
        • infuse acid urine stays basic
      • treatment
        • bicarbonate
    • type II - PCT inability to reabsorb bicarbonate
      • important findings
        • urine pH low (despite bicarbonate wasting)
        • serum K low
        • no renal stones
      • diagnostic test
        • give bicarbonate urine becomes basic
      • treatment
        • high dose bicarbonate
        • thiazide diuretics
    • type IV - a diabetic patient, inability to respond to aldosterone
      • important findings
        • urine pH low
        • serum K high
        • no renal stones
      • diagnostic test
        • urine sodium content (will be elevated)
      • treatment
        • fludrocortisone (highest mineralocorticoid activity steroid)
 

 



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(M2.RL.205) A 40-year-old African American female presents to the emergency room complaining of right-sided, colicky flank pain. Past medical history includes systemic lupus erythematosus, and she has been hospitalized twice for nephrolithiasis in the past year. Serum laboratory values are notable for the following:

Sodium: 138 mEq/L
Potassium: 2.9 mEq/L
Bicarbonate: 15 mEq/L
Chloride: 112 mEq/L

CT scan of the abdomen and pelvis is shown in Figure A. You suspect the patient’s current episode is related to a chronic condition. Which of the following is the most likely diagnosis?
Topic Review Topic
FIGURES: A          

1. Renal tubular acidosis (RTA) type 1
2. Renal tubular acidosis (RTA )type 2
3. Renal tubular acidosis (RTA) type 4
4. Hartnup syndrome
5. Fanconi’s syndrome

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