Difference between revisions of "Renal tubular acidosis"

(Background)
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*Diagnostic classification starts with low, normal, or high serum potassium
 
*Diagnostic classification starts with low, normal, or high serum potassium
 
*Differentiate from [[uremia]] in which acidosis is anion gap
 
*Differentiate from [[uremia]] in which acidosis is anion gap
 +
 +
==Differential==
 +
*See [[metabolic acidosis]]
 +
 +
==Workup==
 +
*ABG or VBG
 +
*BMP, phos, mag
 +
*Urine pH
 +
*Urine electrolytes - Na, K, Cl, Ca, Cr
 +
*Plasma aldosterone and cortisol for type IV RTA
 +
*Note that when hyperkalemia is present, aldosterone should be elevated, so a "normal" aldosterone level may be relatively low
 +
 +
==Etiologies==
 +
*Type II RTA
 +
**[[Multiple myeloma]]
 +
**[[Amyloidosis]]
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**Drugs - ifosfamide, [[acetazolamide]]
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**Heavy metals ([[Lead]], mercury, copper/Wilson's)
 +
**Vitamin D deficiency, rickets, hypophosphatemia
 +
**[[Paroxysmal nocturnal hemoglobinuria]]
 +
**Renal transplant
 +
**Fanconi's syndrome
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**Familial
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**Primary metabolic (cystinosis, von Gierke's)
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*Type I RTA
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**Autoimmune - [[Sjogren's]], [[SLE]], [[RA]]
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**Drugs - [[Lithium]], [[amphotericin B]], ifosfamide
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**[[Sickle cell disease]]
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**[[Cirrhosis]]
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**Obstructive uropathy
 +
**Renal transplant
 +
**Familial (decreased H+/K+-ATPase, Na+/K+-ATPase activity)
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*Type IV RTA
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**Aldosterone deficiency or resistance
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**Diabetic nephropathy (hyporenin/hypoaldosteronism)
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**Obstructive uropathy
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**Chronic tubulointerstitial disease
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**Potassium-sparing diuretics
 +
**Heparin induced adrenal insufficiency
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 +
==Features and Treatment==
 +
*Mild acidosis in adults with bicarb > 20 mEq/L may not require Tx
 +
*Children should be treated due to impaired growth
 +
*For type I and II RTA, treat all children and infants
 +
**Generally, 5-15 mEq/kg/day oral bicarbonate
 +
**May require IV bicarbonate for severe acidosis
 +
**PO potassium supplements
 +
**Treat adults with bicarb < 18-20 mEq/L
 +
**Treat underlying d/o (Vitamin D, etc.)
 +
 +
===Proximal Tubular Acidosis===
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*Type II RTA - reduced bicarbonate reabsorption
 +
**[[Hypokalemia]]
 +
**Serum bicarb 12-20 mEq/L generally
 +
**Urine pH < 5.5, but can be variable
 +
*Urine pH > 5.5 if undergoing alkali therapy
 +
 +
===Distal Tubular Acidosis===
 +
*Type I RTA - impaired H+ and ammonium secretion
 +
**[[Hypokalemia]]
 +
***Normokalemia may be seen in chronic interstitial renal disease
 +
**Serum bicarb may be < 10 mEq/L
 +
**Urine pH > 5.5
 +
**Urinary anion gap > 50 mEq/L = Na + K - Cl
 +
**[[Nephrolithiasis]], calcium stones from chronic acidosis causing bone resorption and hypercalciuria
 +
 +
 +
===Type IV RTA===
 +
*Also distal tubular acidosis
 +
**[[Hyperkalemia]]
 +
**Mild acidosis, with bicarb generally > 17 mEq/L
 +
**Urine pH < 5.5
 +
*Serum aldosterone and cortisol levels to determine between:
 +
**Adrenal insufficiency, Addison's (low aldosterone, low cortisol)
 +
**Selective aldosterone deficiency (low aldosterone, normal cortisol)
 +
**Aldosterone resistance (nl to high aldosterone, nl to high cortisol)
  
 
==Sources==
 
==Sources==

Revision as of 21:40, 2 May 2016

Background

  • Hyperchloremic metabolic acidosis, non-anion gap
  • Diagnostic classification starts with low, normal, or high serum potassium
  • Differentiate from uremia in which acidosis is anion gap

Differential

Workup

  • ABG or VBG
  • BMP, phos, mag
  • Urine pH
  • Urine electrolytes - Na, K, Cl, Ca, Cr
  • Plasma aldosterone and cortisol for type IV RTA
  • Note that when hyperkalemia is present, aldosterone should be elevated, so a "normal" aldosterone level may be relatively low

Etiologies

  • Type II RTA
  • Type I RTA
  • Type IV RTA
    • Aldosterone deficiency or resistance
    • Diabetic nephropathy (hyporenin/hypoaldosteronism)
    • Obstructive uropathy
    • Chronic tubulointerstitial disease
    • Potassium-sparing diuretics
    • Heparin induced adrenal insufficiency

Features and Treatment

  • Mild acidosis in adults with bicarb > 20 mEq/L may not require Tx
  • Children should be treated due to impaired growth
  • For type I and II RTA, treat all children and infants
    • Generally, 5-15 mEq/kg/day oral bicarbonate
    • May require IV bicarbonate for severe acidosis
    • PO potassium supplements
    • Treat adults with bicarb < 18-20 mEq/L
    • Treat underlying d/o (Vitamin D, etc.)

Proximal Tubular Acidosis

  • Type II RTA - reduced bicarbonate reabsorption
    • Hypokalemia
    • Serum bicarb 12-20 mEq/L generally
    • Urine pH < 5.5, but can be variable
  • Urine pH > 5.5 if undergoing alkali therapy

Distal Tubular Acidosis

  • Type I RTA - impaired H+ and ammonium secretion
    • Hypokalemia
      • Normokalemia may be seen in chronic interstitial renal disease
    • Serum bicarb may be < 10 mEq/L
    • Urine pH > 5.5
    • Urinary anion gap > 50 mEq/L = Na + K - Cl
    • Nephrolithiasis, calcium stones from chronic acidosis causing bone resorption and hypercalciuria


Type IV RTA

  • Also distal tubular acidosis
    • Hyperkalemia
    • Mild acidosis, with bicarb generally > 17 mEq/L
    • Urine pH < 5.5
  • Serum aldosterone and cortisol levels to determine between:
    • Adrenal insufficiency, Addison's (low aldosterone, low cortisol)
    • Selective aldosterone deficiency (low aldosterone, normal cortisol)
    • Aldosterone resistance (nl to high aldosterone, nl to high cortisol)

Sources