Rarely used methods for investigating portosystemic shunts in dogs

Background: In dogs with portosystemic shunting (PSS) or chronic liver disease metabolic functions of the liver are disrupted, resulting in increased concentrations of ammonia, amino acids and uric acid in the blood. This is associated with hepatic encephalopathy and often excretion of ammoniumurate crystals in the urine. Objective: The aim of this study was to apply seldom-used methods such as electron dispersive analysis (EDA) for urinary crystal investigation and measurement of serum aromatic amino acids (AAA) and blood ammonia concentrations to investigate a case with PSS. Methods: Scanning electron microscopy with EDA was used to determine crystal type from urine sediment. Blood ammonia levels were measured using a portable ammonia meter. AAA concentrations were analysed in a human laboratory and compared with an age-matched control dog. Results: AAA and blood ammonia concentration were elevated in the patient. EDA revealed the presence of sodium and potassium urate crystals in the urine sediment. Conclusions: Blood ammonia and serum AAA are useful tests for investigation of PSS providing additional information for clinicians assessing dogs with hepatic dysfunction. Measurement of serum AAA concentrations are routinely performed for people but infrequently applied in animals, although testing can be available through human laboratories. EDA as a new, semi-quantitative method for examining urinary crystals can be effectively used to identify a morphologically unidentifiable urinary crystal type in PSS dogs. Because many urinary crystals are morphologically similar, crystal analysis can be useful to determine their content and hence their pathogenesis. This information is especially useful when the typical ammonium biurate crystals are absent.