Selective screening for distal renal tubular acidosis in recurrent kidney stone formers: initial experience and comparison of the simultaneous furosemide and fludrocortisone test with the short ammonium chloride test

Distal renal tubular acidosis (dRTA) is associated with renal stone disease, and it often needs to be considered and excluded in some recurrent calcium kidney stone formers (KSFs). However, a diagnosis of dRTA, especially when 'incomplete', can be missed and needs to be confirmed by a urinary acidification (UA) test. The gold standard reference test is still the short ammonium chloride (NH 4 Cl) test, but it is limited by gastrointestinal side effects and occasionally failure to ingest sufficient NH 4 Cl. For this reason, the furosemide plus fludrocortisone (F+F) test has been proposed as an easier and better-tolerated screening test. The aim of the present study was to assess the usefulness of the F+F test as a clinical screening tool for dRTA in a renal stone clinic.