Pathophysiological and physicochemical basis of ammonium urate stone formation in dolphins

Cynthia R. Smith, John R. Poindexter, Jennifer M. Meegan, Ion Alexandru Bobulescu, Eric D. Jensen, Stephanie Venn-Watson, Khashayar Sakhaee

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Purpose Nephrolithiasis is increasingly reported in bottle-nosed dolphins. All cases to date have been ammonium urate nephrolithiasis. Materials and Methods A case-control study was performed in dolphins with and without evidence of nephrolithiasis to identify biomarkers and risk factors associated with stone formation in a managed population. Dolphins were sampled in fasting and postprandial states to study the effect of dietary factors on serum and urinary biochemistry. Urine was continuously collected for 6 hours via catheter and divided into 3, 2-hour collections with a bolus fish meal given after completing the first collection. Blood was sampled at the beginning of the fasting period and the end of the postprandial period. Results There were no significant differences in serum and urine chemistry or acid-base profiles between dolphins with vs without stones at baseline or postprandially. This suggests that cases and controls represent a continuum of stone risk. On analysis combining cases and controls in a single cohort we noted significant postprandial increases in urinary uric acid, sulfate and net acid excretion accompanied by increased urinary ammonium excretion and a commensurate increase in urine pH. The supersaturation index of ammonium urate increased more than twofold postprandially. Conclusions These findings suggest that dolphins are susceptible to ammonium urate nephrolithiasis at least in part because a high dietary load of acid and purines results in a transient but marked increase in the urinary supersaturation of the sparingly soluble ammonium urate salt.

Original languageEnglish (US)
Pages (from-to)260-266
Number of pages7
JournalJournal of Urology
Volume192
Issue number1
DOIs
StatePublished - Jul 2014

Keywords

  • bottle-nosed dolphin
  • kidney
  • nephrolithiasis
  • risk
  • uric acid

ASJC Scopus subject areas

  • Urology

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