[Pathophysiology and diagnosis of renal tubular acidosis]

Intrinsic defects in tubular transport mechanisms of the kidney may cause impairment of urinary acidification or a loss of base equivalents, thereby inducing systemic metabolic acidosis. Different types of this disorder termed renal tubular acidosis (RTA) can be distinguished based on the localization of the disturbance along the nephron (proximal vs. distal) and their association with potassium transport (hypo-/hyperkalemic). Except for the proximal type RTA results in positive acid balance and negatively impacts on bone metabolism and the formation of kidney stones. The diagnosis is based on analysis of acid/base status, urinary pH and determination of ammonium excretion after an oral acid load. Both functional defects of specific tubular transport mechanisms and global impairment of renal tubular function can be causative of RTA. Their therapy is based on treatment of the primary disease process and correction of acidosis by alkali supplementation.