RENAL TUBULAR ACIDOSIS

Definition: a group of disorders of tubular function that lead to hyperchloremic metabolic acidosis in the presence of preserved glomerular function.

Normal renal acid secretion: Excretes 50-100mmol non-carbonic acid/day. 3 essential functions: 1) proximal reabsorption of bicarb, 2) proximal synthesis of NH4+, 3) distal secretion of H+. NET ACID EXCRETION = titrable acid + NH4+ - urinary loss of HCO3-.

Types of RTA:

1. Proximal (Type II): defect in reabsorption of HCO3- (lowered “threshold”) and decreased NH4+ synthesis.

2. Distal (Type I): decreased distal H+ secretion. 4 mechanisms: secretory defect (impaired proton pump), voltage defect (unfavorable electrical gradient), permeability defect (