To report the presence of urolithiasis in dogs long-term after gradual attenuation of congenital extrahepatic portosystemic shunts (cEHPSS).
25 client-owned dogs that underwent gradual attenuation of a cEHPSS, of which 19 had a closed cEHPSS and 6 developed multiple acquired portosystemic shunts (MAPSS) following surgery.
A retrospective study with prospective follow-up was performed. Dogs that underwent cEHPSS surgery and had their postoperative cEHPSS status determined by transsplenic portal scintigraphy or CT angiography 3 months postoperatively were prospectively contacted and invited for a long-term follow-up visit (a minimum of 6 months postoperatively). Retrospective data were collected, and during the prospective follow-up visit a thorough history, blood tests and urinalysis, and ultrasonography of the urinary tract were performed to assess the presence of urinary signs and urolithiasis.
Of 25 included dogs, 1 of 19 (5%) dogs with closed cEHPSS and 4 of 6 (67%) dogs with MAPSS had urolithiasis at long-term follow-up. Three (50%) dogs with MAPSS developed new uroliths. Long-term, dogs with closed cEHPSS that initially presented with and without urolithiasis had significantly less urolithiasis compared to dogs with MAPSS (P = .013 and P = .010, respectively). In the 4 dogs with closed cEHPSS that initially presented with nephrolithiasis, nephroliths became smaller or were no longer visible at the long-term follow-up visit.
Dogs that developed MAPSS following cEHPSS surgery are at greater risk of urolithiasis compared to those with closed cEHPSS. Furthermore, ammonium urate uroliths might dissolve if portosystemic shunting ceases to exist.
OBJECTIVE To compare ammonia concentrations in arterial blood, venous blood, and CSF samples of dogs with and without extrahepatic portosystemic shunts (EHPSS).
ANIMALS 19 dogs with congenital EHPSS and 6 healthy control dogs.
PROCEDURES All dogs underwent a physical examination and then were anesthetized for transsplenic portal scintigraphy to confirm the presence or absence of EHPSS. While dogs were anesthetized, arterial and venous blood samples and a CSF sample were simultaneously collected for determination of ammonia concentration, which was measured by use of a portable blood ammonia analyzer (device A) and a nonportable biochemical analyzer (device B). Results were compared between dogs with EHPSS and control dogs.
RESULTS Arterial, venous, and CSF ammonia concentrations for dogs with EHPSS were significantly greater than those for control dogs. For dogs with EHPSS, ammonia concentrations in both arterial and venous blood samples were markedly increased from the reference range. There was a strong positive correlation between arterial and venous ammonia concentrations and between blood (arterial or venous) and CSF ammonia concentrations.
CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that blood and CSF ammonia concentrations in dogs with EHPSS were greater than those for healthy dogs and were strongly and positively correlated, albeit in a nonlinear manner. This suggested that the permeability of the blood-brain barrier to ammonia may be abnormally increased in dogs with EHPSS, but further investigation of the relationship between blood or CSF ammonia concentration and clinical signs of hepatic encephalopathy or the surgical outcome for dogs with EHPSS is warranted.