There are three major forms of renal tubular acidosis (RTA):

 distal (type 1), 

proximal (type 2), 

 hyperkalemic.

 Hyperkalemic RTAs include

 hypoaldosteronism (type 4) and voltage-dependent RTA,

 

which is sometimes considered a subtype of distal RTA. These major forms of RTA differ in their pathophysiology and clinical manifestations (table 1) (see 'Classification' above):

Characteristics of the different types of renal tubular acidosis

  Hypokalemic RTA Hyperkalemic RTA 

Type 1 RTA Type 2 RTA Hypoaldosteronism (Type 4 RTA) Distal tubule sodium transport defects 

Primary defect

 Impaired distal acidification.

 Reduced proximal HCO3 reabsorption.

 Decreased aldosterone secretion or aldosterone resistance.

 Reduced sodium reabsorption. 

Plasma HCO3 

Variable.May be below 10 mEq/L

 Usually 12 to 20 mEq/L

 Usually greater than 17 mEq/L

Usually greater than 17 mEq/L. 

Urine pH Greater than 5.3. 

Variable.

Greater than 5.3 if the serum HCO3 exceeds the proximal tubule's HCO3 reabsorptive threshold. Less than 5.3 when the serum HCO3 is reduced to levels that can be reabsorbed despite defective proximal tubule HCO3 reabsorption. 

Variable.

Usually greater than 5.3. 

Variable.

Usually greater than 5.3. 

Plasma potassium Usually reduced, but hyperkalemic forms exist; hypokalemia largely corrects with alkali therapy. Normal or reduced; made worse by bicarbonaturia induced by alkali therapy. Increased; correcting the hyperkalemia alone will improve the acidosis by increasing ammonium availability. Increased; correcting the hyperkalemia alone will improve the acidosis by increasing ammonium availability. 

Urine anion gap Positive Negative Positive Positive 

Urine calcium/creatinine ratio Increased Normal Normal Normal 

Nephrolithiasis/nephrocalcinosis Yes No No No 

RTA: renal tubular acidosis; HCO3: bicarbonate.

YESTERDAY

  

●

Theophylline: Drug information

●

Theophylline poisoning

    

September 18, 2020

 

●

Graphic: CD4:CD8 T lymphocyte ratios in diseases presenting with lymphocytic alveolitis

●

Role of bronchoalveolar lavage in diagnosis of interstitial lung disease

●

Foscarnet: An overview