Asian small‐clawed otter (Aonyx cinerea) urolithiasis prevalence in North America

Abstract

AbstractThe prevalence of urolithiasis in the North American Asian small‐clawed otter (Aonyx cinerea) population was determined through a retrospective survey. A questionnaire regarding diet and radiographic or necropsy evidence of urolithiasis was sent to the 16 North American institutions or individuals listed in the Asian Small‐Clawed Otter North American Regional Studbook. Completed forms were returned by 75% of questionnaire recipients.Individual surveys or necropsy reports were received for 79.8% of the living or dead animals listed as comprising the North American population. Renal calculi were detected in 66.1%, and cystic calculi in 23.2%, of the captive adult population that had been radiographed or necropsied. All otters with cystic calculi also had renal calculi. Bilateral renal calculi occurred in 83.8% of affected otters. Both males (61.2%) and females (72%) were frequently affected. The prevalence of urolithiasis in wild‐born otters was 76.7%, and in adult (≥1 year) captive‐born otters it was 53.8%. The higher prevalence in wild‐born otters may be a reflection of the older mean age at which they were first evaluated. In the overwhelming majority of otters with renal calculi, the calculi were multiple and diffusely distributed throughout the renal parenchyma. Renal and cystic calculi analyzed were primarily composed of calcium oxalate or urates. Glucosuria was infrequently reported. Necropsies of dependent neonates (≤ 2 months old) that died revealed cystic calculi in one animal.Renal disease was the cause of, or a contributing factor in, the deaths of all older animals whose necropsy reports were reviewed. The captive diet may be a contributing factor to urolith formation and progression.