Renal tubular acidosis (RTA) is comprised of a diverse group of congenital or acquired diseases with the common denominator of defective renal
acid excretion with protean manifestation, but in adults, recurrent
kidney stones and
nephrocalcinosis are mainly found in presentation.
Calcium phosphate (CaP) stones and
nephrocalcinosis are frequently encountered in distal hypokalemic RTA type I. Alkaline urinary pH, hypocitraturia, and, less frequently,
hypercalciuria are the tripartite lithogenic factors in distal RTA (
dRTA) predisposing to CaP stone formation; the latter 2 are also commonly encountered in other causes of
urolithiasis. Although the full blown syndrome is easily diagnosed by conventional clinical criteria, an attenuated forme fruste called incomplete
dRTA typically evades clinical testing and is only uncovered by provocative
acid-loading challenges. Stone formers (SFs) that cannot acidify urine of pH < 5.3 during
acid loading are considered to have incomplete
dRTA. However, urinary acidification capacity is not a dichotomous but rather a continuous trait, so incomplete
dRTA is not a distinct entity but may be one end of a spectrum. Recent findings suggest that incomplete
dRTA can be attributed to heterozygous carriers of hypofunctional V-
ATPase. The value of incomplete
dRTA diagnosis by provocative testing and genotyping candidate genes is a valuable research tool, but it remains unclear at the moment whether they alter clinical practice and needs further clarification. No randomized controlled trials have been performed in SFs with
dRTA or CaP stones, and until such data are available, treatment of CaP stones are centered on reversing the biochemical abnormalities encountered in the metabolic workup. SFs with type I
dRTA should receive
alkali therapy, preferentially in the form of K-
citrate delivered judiciously to treat the chronic
acid retention that drives both stone formation and
bone disease.