The 13C-galactose breath test (13C-GBT) has been validated for non-invasive, quantitative assessment of liver metabolic function in human medicine, but the use of this test in veterinary medicine has not been investigated.
The aim of this study was to evaluate the application of the 13C-GBT for assessment of canine liver function through evaluation of a group of healthy dogs (n = 23) and a group of dogs with liver dysfunction (n=16) . All dogs in the liver disease group displayed clinical signs of, and results of clinical investigations consistent with, hepatic dysfunction. Furthermore these individuals were subsequently diagnosed with parenchymal liver disease (n = 8) or primary hepatic vascular abnormalities (n = 8) on the basis of hepatic biopsy histopathology and diagnostic imaging.
After withholding food for 12 hours, each dog ingested a test meal consisting 13C-galactose (5mg/kg) and unlabelled galactose (25g/m2) dissolved in skimmed milk. Exhaled breath samples were collected using a face mask, 20 minutes before ingestion of the test meal and then at regular intervals thereafter for 6 hours; samples were stored at room temperature. No adverse effects were observed either during or after the collection period. The proportion of 13CO2/12CO2 in the exhaled breath samples was measured by isotope ratio mass spectrometry. Non-linear regression analysis was used to calculate two mathematical indices (t½ and tmax) to describe the rate of recovery of 13CO2 in breath.
There was no significant difference in values of tmax and t½ in the diseased group compared to the healthy controls, but there was considerable inter-subject variation in both groups. This variation may be due to differences in the rate of gastric emptying among animals, which could preclude detection of alterations in hepatic metabolism of galactose. The results of this study do not support the application of the 13C-GBT for assessment of canine liver function, although the application of this test following intravenous substrate administration may warrant further investigation.
This study was funded by a Comparative Gastroenterology Society research grant.