Abstract
Nephrolithiasis with vaginal calculus was identified in a stranded free-ranging long-beaked common dolphin (Delphinus capensis). Necropsy examination of the sexually mature D. capensis revealed multiple bilateral nephroliths and a 6.4 cm x 4.1 cm x 9.2 cm vaginal calculus weighing 182 g. Concurrently, the animal had a lytic and sclerotic lesion of the lumbar vertebrae with fusion of associated spinous processes. The extracted nephroliths ranged in size from 0.2 cm to 0.4 cm and were composed of 100% ammonium urate, which has been found in captive dolphin populations, while the vaginolith consisted of struvite and calcium carbonate. This disparity of composition suggests that the etiology of the two conditions was not directly related. No infectious agents were identified histologically or by calculi culture. Additionally, Morbillivirus PCR and Brucella PCR were negative, and biotoxin analysis and heavy metal concentrations were within normal limits. The vertebral lesion was considered incidental. The composition of the vaginolith suggests that bacterial vaginitis could have served as the predisposing condition. Staphylococcus sp. was isolated from the uterus, and Staphylococcus sp. producing urease has been associated with formation of struvite calculi.1 Although previously reported vaginoliths in common dolphins have been linked with fetal remains, this case is more similar to struvite vaginoliths reported in other species.2-6 Renal lesions included chronic tubulointerstitial nephritis with tubular degeneration and loss likely secondary to the presence of the nephroliths. The etiology of ammonium urate nephrolithiasis in managed care is linked to diet and age.7-9 If environmental changes cause a shift in prey species, the risk of nephrolithiasis in free-ranging cetaceans could increase. Careful surveillance for nephroliths in free-ranging populations should be considered by researchers.
Acknowledgements
Thank you Keiko Sherman, Holly Baijnuth, and Alexa Kownacki for assistance with the necropsy examination, and Katie Colegrove, David Gaspar, Tracey Goldstein, Kathi Lefebvre, Victoria Palmer, Sarena Sunico, and Lisa Ulrich for diagnostic services. Hill’s Pet Nutrition provided financial support for calculi composition analyses.
* Presenting author
Literature Cited
1. Osborne C, Klausner J, Krawiec D, Griffith D. 1981. Canine struvite urolithiasis: problems and their dissolution. Journal of the American Veterinary Medical Association. 179(3):239–244.
2. McFee WE, Osborne CA. 2004. Struvite calculus in the vagina of a bottlenose dolphin (Tursiops truncatus). Journal of Wildlife Diseases. 40(1):125–128.
3. Norman SA, Garner MM, Berta S, Dubpernell S, Klope M. 2011. Vaginal calculi in a juvenile harbor porpoise (Phocoena phocoena). Journal of Zoo and Wildlife Medicine. 42(2):335–337.
4. Benirschke K, Henderson JR, Sweeney JC. 1984. A vaginal mass, containing fetal bones, in a common dolphin, Delphinus delphis. Report of the International Whaling Commission (Special Issue 6).
5. Sawyer JE, Walker WA. 1977. Vaginal calculi in the dolphin. Journal of Wildlife Diseases. 13(4):346–348.
6. Woodhouse CD, Rennie III CJ. 1991. Observations of vaginal calculi in dolphins. Journal of Wildlife Diseases. 27(3):421–427.
7. Smith CR, Venn-Watson S, Wells RS, Johnson SP, Maffeo N, Balmer BC, Jensen ED, Townsend FI, Sakhaee K. 2013. Comparison of nephrolithiasis prevalence in two bottlenose dolphin (Tursiops truncatus) populations. Frontiers in Endocrinology. 4:145.
8. Smith CR, Poindexter JR, Meegan JM, Bobulescu IA, Jensen ED, Venn-Watson S, Sakhaee K. 2014. Pathophysiological and physicochemical basis of ammonium urate stone formation in dolphins. The Journal of Urology. 192(1):260–266.
9. Ardente AJ, Wells RS, Smith CR, Walsh MT, Jensen ED, Schmitt TL, Colee J, Vagt BJ, Hill RC. 2017. Dietary cation-anion difference may explain why ammonium urate nephrolithiasis occurs more frequently in common bottlenose dolphins (Tursiops truncatus) under human care than in free-ranging common bottlenose dolphins. Journal of Animal Science. 95(3):1396–1406.