+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

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



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



Nephrology, Dialysis, Transplantation 31(11): 1870-1876



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 (NH4Cl) test, but it is limited by gastrointestinal side effects and occasionally failure to ingest sufficient NH4Cl. 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. We studied 124 patients retrospectively in whom incomplete dRTA was suspected: 71 had kidney stones only, 9 had nephrocalcinosis only and 44 had both. A total of 158 UA tests were performed: 124 F+F and 34 NH4Cl; both tests were completed in 34 patients. The mean age was 45.4 ± 15 years, and 49% of patients were male. The prevalence of complete and incomplete dRTAs was 7 and 13.7%, respectively. Of the 34 patients tested using both tests, 17 (50%) were abnormal and 4 (12%) were normal. Thirteen (39%) patients were abnormal by F+F, but normal by NH4Cl [sensitivity 100% (95% CI 80-100), specificity 24% (95% CI 7-50), positive predictive value 57% (95% CI 37-75), negative predictive value 100% (95% CI 40-100)]. The F+F test is characterized by an excellent sensitivity and negative predictive value, and the diagnosis of incomplete dRTA can be excluded reliably in a patient who acidifies their urine normally with this test. However, its lack of specificity is a drawback, and if there is any doubt, an abnormal F+F test may need to be confirmed by a follow-up NH4Cl test. Ideally, a prospective blinded study in unselected KSFs is needed to accurately assess the reliability of the F+F test in diagnosing, rather than excluding, dRTA.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 058822114

Download citation: RISBibTeXText

PMID: 26961999

DOI: 10.1093/ndt/gfv423


Related references

Furosemide/Fludrocortisone Test and Clinical Parameters to Diagnose Incomplete Distal Renal Tubular Acidosis in Kidney Stone Formers. Clinical Journal of the American Society of Nephrology 12(9): 1507-1517, 2017

Distal renal tubular acidosis in recurrent renal stone formers. Danish Medical Bulletin 36(5): 492-493, 1989

Screening renal stone formers for distal renal tubular acidosis. British Journal of Urology 63(6): 581-583, 1989

Prevalence and metabolic features of distal renal tubular acidosis among 534 non-selected kidney stone formers. European Urology Suppl.s 16(7): E2515-E2516, 2017

Use of the Furosemide Fludrocortisone Test to Clinically Assess Distal Tubular Acidification. American Journal of Kidney Diseases 70(4): 589-591, 2017

Ammonium chloride and the calcium chloride loading test for the diagnosis of renal tubular acidosis. Nihon Rinsho. Japanese Journal of Clinical Medicine 43(9): 1836-1842, 1985

Urinary citrate an alternate to ammonium chloride loading in screening for familial distal renal tubular acidosis. Kidney International 8(6): 415, 1975

The clinical importance of renal tubular acidosis in recurrent renal stone formers. Smith, L H , W G Robertson And B Finlayson (Ed ) Urolithiasis: Clinical And Basic Research; Proceedings Of The 4th International Symposium, Williamsburg, Va , Usa, June 22-26, 1980 Xxvi+1035p Plenum Press: New York, N Y , Usa; London, England Illus P67-70, 1981

A study of recurrent stone formers with special reference to renal tubular acidosis. Urological Research. 23(3): 201-203, 1995

Renal tubular acidosis in recurrent renal stone formers. European Urology 10(1): 55-59, 1984

Renal Tubular Acidosis in Recurrent Renal Stone Formers. European Urology 10(1): 55-59, 1984

Pathophysiology of incomplete renal tubular acidosis in recurrent renal stone formers: Evidence of disturbed calcium, bone and citrate metabolism. Urological Research 21(3): 169-173, 1993

Astrup's capillary blood test and urinary pH as parameters of renal hydrogen-ion elimination. 2. Deviation of acid-base equilibrium and urinary pH following ammonium chloride loading test and their relationships to latent tubular acidosis. Das Deutsche Gesundheitswesen 24(23): 1074-1078, 1969

Astrup's capillary blood test and urinary pH as parameters of renal hydrogen ion elimination. 1. Examination results following oral ammonium chloride loading test in healthy children and children with kidney tubular damage. Das Deutsche Gesundheitswesen 24(20): 945-949, 1969

Urinary acidification assessed by simultaneous furosemide and fludrocortisone treatment: an alternative to ammonium chloride. Kidney International 71(12): 1310-1316, 2007