Renal tubular acidosis
A syndrome of persistent dehydration, hyperchloremia, hypokalemia, metabolic acidosis, and nephrocalcinosis, renal tubular acidosis (RTA) results from the kidneys’ inability to conserve bicarbonate. This disorder occurs as distal RTA (type I, or classic RTA) or proximal RTA (type II). The prognosis is usually good but depends on the severity of renal damage that precedes treatment.
Metabolic acidosis usually results from renal excretion of bicarbonate. However, metabolic acidosis associated with RTA results from a defect in the kidneys’ normal tubular acidification of urine.
Type I RTA results from an inability of the distal tubule to secrete hydrogen ions against established gradients across the tubular membrane. This results in decreased excretion of titratable acids and ammonium, increased loss of potassium and bicarbonate in the urine, and systemic acidosis.
Prolonged acidosis causes mobilization of calcium from bone and eventually hypercalciuria, predisposing the patient to the formation of renal calculi.
Distal RTA may be classified as primary or secondary:
Primary distal RTA may occur sporadically or through a hereditary defect and is most prevalent in females, older children, adolescents, and young adults.
Secondary distal RTA has been linked to many renal and systemic conditions, such as starvation, malnutrition, hepatic cirrhosis, and several genetically transmitted disorders.