title: Pathophysiological and physicochemical basis of ammonium urate stone formation in dolphins.
abstract: OBJECTIVE
  Nephrolithiasis is increasingly reported in bottle-nosed dolphins. All cases to date have been ammonium urate nephrolithiasis.
  
  
  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.
authors: National Marine Mammal Foundation, San Diego, California.
authors: Cynthia R
authors: CR
authors: Smith
authors: Department of Internal Medicine and Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
authors: John R
authors: JR
authors: Poindexter
authors: National Marine Mammal Foundation, San Diego, California.
authors: Jennifer M
authors: JM
authors: Meegan
authors: Department of Internal Medicine and Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
authors: Ion Alexandru
authors: IA
authors: Bobulescu
authors: United States Navy Marine Mammal Program, Space and Naval Warfare Systems Center Pacific, San Diego, California.
authors: Eric D
authors: ED
authors: Jensen
authors: National Marine Mammal Foundation, San Diego, California.
authors: Stephanie
authors: S
authors: Venn-Watson
authors: Department of Internal Medicine and Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas. Electronic address: khashayar.sakhaee@utsouthwestern.edu.
authors: Khashayar
authors: K
authors: Sakhaee
mesh_terms: D000818:Animals; D050681:Bottle-Nosed Dolphin / Q000378:metabolism; D016022:Case-Control Studies; D055598:Chemical Phenomena; D005260:Female; D008297:Male; D053040:Nephrolithiasis / Q000378:metabolism / Q000503:physiopathology / Q000662:veterinary*; D014527:Uric Acid / Q000032:analysis
chemical_list: D014527:Uric Acid
keywords: bottle-nosed dolphin; kidney; nephrolithiasis; risk; uric acid