Renal tubular acidosis: Difference between revisions

Latest revision as of 14:51, 24 March 2024

Definition

Group of diseases characterized by non-anion gap metabolic acidosis and preserved renal function

Types

Type I: Hypokalemic Distal

Caused by defects in distal tubular H+ secretion
Hypokalemia, positive urine anion gap, urine pH >5.5
Etiology
- Hereditary
- Genetic: sickle cell; Fabry disease; Wilson disease; elliptocytosis
- Medullary cystic kidney disease
- Autoimmune: Sjögren syndrome, systemic lupus erythematosus
- Nephrocalcinosis/hypercaliuria
- Dysproteinemias: amyloidosis, cryoglobulinemia, hypergammaglobulinemia
- Drugs: amphotericin B, lithium, analgesic abuse
- Tubulointerstitial disease: reflux nephropathy, obstructive uropathy, kidney transplant rejection

Type II: Proximal

Caused by proximal tubular bicarbonate reabsorption
Hypokalemia, negative urine anion gap, urine pH variable
Etiology
- Primary (hereditary or sporadic)
- Hereditary carbonic anhydrase deficiency
- Fanconi syndrome

Type IV: Hyperkalemic Distal

Caused by impaired ammoniagenesis, often caused by hypoaldosteronism
Hyperkalemia, positive urine anion gap, urine pH <5.5
Etiology
- Primary aldosterone deficiency (Addison disease)
- Hyporeninemic hypoaldosteronism
  - Acute glomerulonephritis
  - Chronic nephropathy
    - Diabetes (most common cause)
    - Systemic lupus erythematosus
    - HIV
- Aldosterone resistance:
  - Tubulointerstitial disease: urinary obstruction, sickle cell disease, medullary cystic kidney disease, and kidney transplant rejection
- Drugs: ACE inhibitors, cyclooxygenase inhibitors, trimethoprim, heparin
Mixed proximal/distal
- Carbonic anhydrase mutations
- Drugs: topiramate

Risk Factors

Type IV: diabetes

Investigations

Serum electrolytes
- Normal anion gap metabolic acidosis
- Hyperkalemia (type IV)
Urine anion gap: UNa + UK - UCl
- If positive, suggests presence of ammonium
- If kidneys are responding properly, the UAG should be negative
- If defect in acid excretion, UAG should be positive
Urine pH

	Type 1	Type 2	Type 4
Acidosis	Severe	Moderate	Mild
Serum K	↓ / ↑†	↓	↑
Serum HCO₃	Variable	10-20	>17
Urine pH	>5.3	<5.3	<5.3
Urine AG	+	±	+

† a hyperkalemic Type 1 RTA is possible with urinary obstruction, sickle cell, lupus, and renal transplant

@@ Line 5: / Line 5: @@
 == Types ==
-=== Type I: hypokalemic distal ===
+=== Type I: Hypokalemic Distal ===
 * Caused by defects in distal tubular H+ secretion
@@ Line 11: / Line 11: @@
 * Etiology
 ** Hereditary
-** Genetic: sickle cell; Fabry disease; Wilson disease; elliptocytosis
+** Genetic: [[Sickle cell disease|sickle cell]]; [[Fabry disease]]; [[Wilson disease]]; [[elliptocytosis]]
-** Medullary cystic kidney disease
+** [[Medullary cystic kidney disease]]
-** Autoimmune: Sjögren syndrome, systemic lupus erythematosus
+** Autoimmune: [[Sjögren syndrome]], [[systemic lupus erythematosus]]
-** Nephrocalcinosis/hypercaliuria
+** [[Nephrocalcinosis]]/[[hypercaliuria]]
-** Dysproteinemias: amyloidosis, cryoglobulinemia, hypergammaglobulinemia
+** Dysproteinemias: [[amyloidosis]], [[cryoglobulinemia]], [[hypergammaglobulinemia]]
-** Drugs: amphotericin B, lithium, analgesic abuse
+** Drugs: [[amphotericin B]], [[Lithium toxicity|lithium]], analgesic abuse
-** Tubulointerstitial disease: reflux nephropathy, obstrctive uropathy, kidney transplant rejection
+** Tubulointerstitial disease: [[reflux nephropathy]], [[obstructive uropathy]], kidney transplant rejection
-=== Type II: proximal ===
+=== Type II: Proximal ===
 * Caused by proximal tubular bicarbonate reabsorption
@@ Line 25: / Line 25: @@
 * Etiology
 ** Primary (hereditary or sporadic)
-** Hereditary carbonic anhydrase deficiency
+** [[Hereditary carbonic anhydrase deficiency]]
-** Fanconi syndrome
+** [[Fanconi syndrome]]
-=== Type IV: hyperkalemic distal ===
+=== Type IV: Hyperkalemic Distal ===
 * Caused by impaired ammoniagenesis, often caused by hypoaldosteronism
 * Hyperkalemia, positive urine anion gap, urine pH &lt;5.5
 * Etiology
-** Primary aldosterone deficiency (Addison disease)
+** [[Primary aldosterone deficiency]] ([[Addison disease]])
 ** '''Hyporeninemic hypoaldosteronism'''
-*** Acute glomerulonephritis
+*** Acute [[glomerulonephritis]]
 *** Chronic nephropathy
-**** '''Diabetes''' (most common cause)
+**** '''[[Diabetes mellitus|Diabetes]]''' (most common cause)
-**** Systemic lupus erythematosus
+**** [[Systemic lupus erythematosus]]
-**** AIDS
+**** [[HIV]]
 ** Aldosterone resistance:
-*** Tubulointerstitial disease: urinary obstruction, sickle cell disease, medullary cystic kidney disease, and kidney transplant rejection
+*** Tubulointerstitial disease: [[urinary obstruction]], [[sickle cell disease]], [[medullary cystic kidney disease]], and kidney transplant rejection
-** Drugs: ACE inhibitors, cyclooxygenase inhibitors, trimethoprim, heparin
+** Drugs: [[ACE inhibitors]], cyclooxygenase inhibitors, [[trimethoprim]], [[heparin]]
 * Mixed proximal/distal
 ** Carbonic anhydrase mutations
-** Drugs: topiramate
+** Drugs: [[topiramate]]
 == Risk Factors ==
-* Type IV: diabetes
+* Type IV: [[Diabetes mellitus|diabetes]]
 == Investigations ==
@@ Line 62: / Line 62: @@
 * Urine pH
+{| class="wikitable"
-{|
 !
 ! Type 1
@@ Line 74: / Line 74: @@
 |-
 | Serum K
-| ↓ / ↑*
+| ↓ / ↑†
 | ↓
 | ↑
 |-
-| Serum HCO<s>3</s>
+| Serum HCO<sub>3</sub>
 | Variable
 | 10-20
@@ Line 94: / Line 94: @@
 |}
-* a hyperkalemic Type 1 RTA is possible with urinary obstruction, sickle cell, lupus, and renal transplant
+* † a hyperkalemic Type 1 RTA is possible with [[urinary obstruction]], [[Sickle cell disease|sickle cell]], [[lupus]], and renal transplant
 [[Category:Nephrology]]