Abstract

Eleven cases of end-stage renal disease (ESRD) were identified in captive polar bears (Ursus maritimus) from eight zoological institutions across the United States and Canada. The index case was identified by submission of a polar bear to Tufts Pathology Service for necropsy, and the remaining cases by searching two databases: annual reports of the Species Survival Plan Taxon Advisory Group and necropsy records from a private diagnostic institution. Ten bears were female, one was male, and the mean age at the time of death was 24 years. The most common clinical signs were lethargy, inappetence, and polyuria/polydipsia. Biochemical findings included azotemia, anemia, hyperphosphatemia, and isosthenuria. Histological examination commonly showed glomerulonephropathies and interstitial fibrosis.

The prevalence of ESRD in captive polar bears in the United States was estimated by searching the database of a private diagnostic institution for all polar bears that were submitted for cause of death determination between 1995 and 2011. Thirty-four polar bears were identified, seven of which died from ESRD. ESRD was the most common cause of death or reason for euthanasia with an estimated prevalence of over 20%. Further research is needed to discern the etiology of this apparently common disease of captive polar bears.