Abstract

We report the first known case of xanthine nephrolithiasis in an aquatic mammal. Nephrolithiasis has been reported in several aquatic mammals including bottlenose dolphins (Tursiops truncatus), small clawed otter (Amblonyx cinereus), northern elephant seal (Mirounga angustirostris), Florida manatee (Trichechus manatus latirostris), and California sealions (Zalophus californianus).^1,2,3,4 Stone composition in previous cases, was predominantly calcium oxalate or ammonium acid urate, not pure xanthine. An 11-month-old, female, giant river otter (Pteronura brasiliensis) presented with acute onset anorexia and lethargy of three days duration. Post-mortem revealed extensive bilateral nephrolithiasis. Stone analysis revealed 100% xanthine composition. Biochemistry confirmed renal compromise with blood urea nitrogen of 368 mg/dl and creatinine of 9.5 g/dl. Phosphorus and calcium were elevated at 32.9 mg/dl and 19.6 mg/dl. Histologic exam revealed marked nephrolithiasis with associated tubular necrosis and metastatic gastric mineralization. Despite renal lesions, the otter was in excellent body condition at the time of death. Nutrient analysis, including mineral and purine analyses, is being performed to assess the potential risk of diet contributing to stone formation. A review of archives at Northwest ZooPath identified 7 additional cases of nephrolithiasis in this species; stone analysis is pending. Xanthine urolithiasis is rare in veterinary medicine with only 3 previously reported cases in domestic mammals and appears to be a consequence of an autosomal recessive gene mutation.^5,6 The potential role of diet and genetics in xanthine nephrolithiasis in the small inbred population of Giant river otters under human care needs to be investigated further, to assess long term health management of this species.

Acknowledgements

The authors wish to thank the giant river otter keepers at The Dallas World Aquarium and veterinary technician Nikki Gomas for their care and assistance with this case.

* Presenting author

Literature Cited

1.  Venn-Watson S, Smith CR, Johnson S, Daniels R, Townsend F. 2010. Clinical relevance of urate nephrolithiasis in bottlenose dolphins Tursiops truncatus. Diseases of Aquatic Organisms. 89(2):167–77.

2.  Grove RA, Bildfell R, Henny CJ, Buhler DR. 2003. Bilateral uric acid nephrolithiasis and ureteral hypertrophy in a free-ranging river otter (Lontra canadensis). Journal of Wildlife Diseases. 39(4):914–917.

3.  Dennison S, Gulland F, Haulena M, De Morais H, Colegrove K. 2007. Urate nephrolithiasis in a northern elephant seal (Mirounga angustirostris) and a California sea lion (Zalophus californianus). Journal of Zoo and Wildlife Medicine. 3(1):114–120.

4.  Keller M, Moliner JL, Vásquez G, et al. 2008. Nephrolithiasis and pyelonephritis in two West Indian manatees (Trichechus manatus spp.). Journal of Wildlife Diseases. 44(3):707–711.

5.  Pais VM, Lowe G, Lallas CD, Preminger GM, Assimos DG. 2006. Xanthine urolithiasis. Urology. 67(5):1084–1090.

6.  White R. Naturally occurring xanthine urolithiasis in a domestic shorthair cat. 1997. Journal of Small Animal Practice. 38(7):299–230.