This study describes two cases of urolithiasis-related mortality in Asian small-clawed otters (Aonyx cinerea) raised together for over 10 years. Case 1 had multiple renal and bladder stones without clinical signs and died during surgery for stone removal. Case 2, which harbored more extensive renal calculi, also showed no clinical signs but died suddenly from hydronephrosis and renal failure caused by bilateral obstruction of the renal pelvis. In both cases, the uroliths were composed of calcium oxalate. These results highlight the importance of regular examinations in captive otters.

Abstract
ACKNOWLEDGEMENTS
CONFLICT OF INTEREST
REFERENCES

• Minjong Ha(Seoul Children’s Grand Park, Seoul 04991, Korea)
• Jiyong Uhm(Seoul Children’s Grand Park, Seoul 04991, Korea)
• Haneol Park(Seoul Children’s Grand Park, Seoul 04991, Korea)
• Minkyung Kim(Seoul Children’s Grand Park, Seoul 04991, Korea, Graduate of Veterinary Biosecurity and Protection, Chungbuk National University, Cheongju, Chungbuk 28644, Korea)
• Soochong Kim(Graduate of Veterinary Biosecurity and Protection, Chungbuk National University, Cheongju, Chungbuk 28644, Korea, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk 28644, Korea)
• Seung-Hun Lee(Graduate of Veterinary Biosecurity and Protection, Chungbuk National University, Cheongju, Chungbuk 28644, Korea, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk 28644, Korea) Corresponding author
• Sungin Lee(College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk 28644, Korea)
• Dong-Hyuk Jeong(College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk 28644, Korea, Wildlife Center of Chungbuk, Cheongju, Chungbuk 28116, Korea)