Diagnostic Value of Fasting Plasma Ammonia and Bile Acid Concentrations in the Identification of Portosystemic Shunting in Dogs

Abstract

Portosystemic shunting occurs frequently either as congenital anomalies of the portal vein (PVA) or as acquired shunting (AS) due to portal hypertension secondary to parenchymal liver disease or portal vein thrombosis. The 2 most commonly used screening tests for portosystemic shunting are bile acid and plasma ammonia concentrations. The purpose of this study was to compare the 12-hour fasting plasma ammonia (AMM) and bile acid concentration (BA) as tests for diagnosing portosystemic shunting. Medical records of 337 dogs were used in which AMM and BA were measured simultaneously and in which portosystemic shunting was confirmed or excluded. These dogs were divided into 2 groups (group 1: portosystemic shunting present, n 5 153, and group 2: portosystemic shunting absent, n 5 184). Group 1 was subdivided into 2 subgroups (group 1a: PVA, n 5 132 and group 1b: AS, n 5 21). The sensitivity of AMM in detecting PVA was 100% and of BA was 92.2%. For portosystemic shunting in general (PVA or AS), the sensitivity of AMM was 98% and that of BA was 88.9%. The specificity in the total population of AMM was 89.1% and that of BA was 67.9%. If only dogs with liver diseases were included with (n 5 153) or without (n 5 28) shunting, the specificity of AMM to detect shunting was 89.3% and that of BA was 17.9%. In conclusion, AMM is a highly sensitive and specific parameter to detect PVA and portosystemic shunting in a general population and in dogs with liver disease, whereas BA is somewhat less sensitive and considerably less specific.

Comparison of Postprandial and Ceruletide Serum Bile Acid Stimulation in Dogs

“…2,23,24 A recent study found baseline SBA concentrations to have a sensitivity of 92.2% for the detection of a congenital PSS and 81% for acquired shunting. 9 In our study, none of the dogs with tracheal collapse had increased baseline SBA and 2 of 11 dogs with a PSS were missed with only a fasting SBA measurement. These findings clearly indicate that baseline SBA concentrations are not consistently elevated in dogs with hepatic dysfunction and that the determination of stimulated SBA can give additional information when liver disease is suspected.…”

“…Measurements of SBA in dogs with PSS resulted in a sensitivity of 64-100% in blood samples from fasted patients 3,4,9 and 100% in samples taken postprandially. [2][3][4] However, several factors can influence the postprandial (PP) values of SBA.…”

ACVIM consensus statement on the diagnosis and treatment of chronic hepatitis in dogs

“…[197][198][199] However, their sensitivity, particularly for early stage disease, is inadequate, which makes them poor screening tests for CH and thus should not be used as the basis for deciding to pursue hepatic biopsy. 189,192,200 However, TSBA concentrations are uniformly increased when portosystemic shunting is present, thus their sensitivity for detecting cirrhosis and the presence of APSS is high. 189 Dogs with cholestasis (ie, hyperbilirubinemia) associated with hepatic disease will always have increased TSBA.…”

“…Hyperammonemia has similar sensitivity to detecting CH or cirrhosis and APSS as do TSBA, and it is somewhat more specific because it is not affected by cholestasis. 200 However, it is much more technically difficult to accurately measure blood ammonia concentrations. 197,[201][202][203][204] Although hyperammonemia infers the presence of HE, HE can develop in the absence of high blood ammonia concentrations.…”

Efficacy of orally administered sodium benzoate and sodium phenylbutyrate in dogs with congenital portosystemic shunts

“…6 Hyperammonemia in dogs is mostly secondary to congenital portosystemic shunts (CPSS). [7][8][9] These CPSS are vascular anomalies that connect the portal vein to the systemic circulation, thereby bypassing the hepatic sinusoids. 10 As a result, blood flow from the portal vein through the liver parenchyma can be decreased by >95%, 11 carrying intestinal absorption products (eg, NH 3 ) directly into the systemic circulation.…”