Serum unconjugated bile acids as a test for intestinal bacterial overgrowth in dogs

Small intestinal bacterial overgrowth (SIBO) has a high incidence in dogs a nd, as in humans, is difficult to diagnose. The aim of this study was to de termine the diagnostic significance of serum unconjugated bile acid concent rations in dogs with bacterial overgrowth. Fasting sera were obtained from 23 dogs: 10 with culture-proven SIBO, 8 with indirectly diagnosed SIBO (nor mal pancreatic function but small intestinal disease associated with subnor mal serum cobalamin and supranormal folate concentrations), and 5 healthy c ontrols. Unconjugated bile acids were determined using gas chromatography-m ass spectrometry after isolation by liquid-solid extraction and anion-excha nge chromatography. Mean serum unconjugated bile acid concentrations were s ignificantly elevated in dogs with SIBO (mean +/- SD: 0.91 +/- 1.03 mu mol/ liter), and in dogs with indirectly diagnosed SIBO (2.11 +/- 2.20 mu mol/li ter) compared to clinically healthy dogs (0.015 +/- 0.015 mu mol/liter, P < 0.005). Cholic acid was the predominant unconjugated bile acid in the seru m of dogs with SIBO. In conclusion serum unconjugated bile acid concentrati ons of healthy dogs are significantly lower than reported values for humans , and this fraction represents a relatively small proportion (0-2.3%; mean 0.8%) of the total bile acids in dogs. Unconjugated bile acids increased 10 - to 20-fold in dogs with SIBO indicating the clinical utility of serum unc onjugated bile acids for diagnosis of intestinal bacterial overgrowth in do gs.