Retrospective analysis of the incidence and clinicopathological findings associated with ammonium urate urolithiasis in dogs with congenital portosystemic shunts: 363 cases (2010‐2023)

Objectives
To assess the incidence and clinical findings associated with the presence of ammonium urate urolithiasis in dogs with congenital portosystemic shunts.

Materials and Methods
A retrospective review of dogs diagnosed with extrahepatic portosystemic shunts or intrahepatic portosystemic shunts in 15 referral hospitals between 2010 and 2023. Data including signalment, clinical signs, physical examination findings and clinicopathologic test results at the time of the diagnosis were collected, and the presence of ammonium urate urolithiasis was recorded.

Results
A total of 363 dogs were included. The overall incidence of ammonium urate urolithiasis was 19.3%. Dogs with extrahepatic portosystemic shunts were more likely to have urolithiasis compared to those with intrahepatic portosystemic shunts (32.2% vs. 8.0%). Dogs with urolithiasis were older (median 40 vs. 8 months) and more likely to be neutered males (51.4% vs. 9.8%). Ammonia was significantly lower in dogs with urolithiasis. Dogs with urolithiasis were more likely to have haematuria on dipstick analysis and sediment examination.

Clinical Significance
Dogs with extrahepatic portosystemic shunts were more likely to have urolithiasis when compared to dogs with intrahepatic portosystemic shunts. Dogs with higher ammonia levels were less likely to have ammonium urate urolithiasis, and older dogs, neutered males, or those with evidence of haematuria had an increased incidence of urolithiasis.