The use of serum bile acids (SBA) as an indicator of hepatic function has been described in the human literature since the mid-seventies and first appeared in the veterinary literature in the early eighties. SBA have been measured in cetaceans with suspected hepatic dysfunction, however, the significance of elevated values has been difficult to determine without a standardized method of sampling and normal reference ranges for comparison. To date, there has been no published information regarding SBA determination in the cetacean medical literature and normal baseline ranges for the evaluation of clinically ill animals are absent. Serum enzyme levels are routinely relied upon for the diagnosis and monitoring of hepatic disease. The non-specific tissue origin of many of these enzymes, however, does not allow for specific organ system evaluation. SBA has been shown in small animal medicine, to have both a high sensitivity and specificity in determining hepatobiliary function or the presence of portosystemic vascular anomalies. Other hepatic function tests (i.e., sulfobromophthalein clearance and ammonia tolerance) have been utilized in domestic animal medicine but require the administration of exogenous substances that can be potentially toxic to animals with hepatic compromise.

Seven Pacific white-sided dolphins, Lagenorhyncus obliqui dens, were fasted overnight (12-16 hours) and a fasting blood sample was obtained. The animals were then fed a diet of herring, smelt and capelin (1.1 to 2.5 kg) and blood was sampled at 60, 90, 120 and 180 minutes following this feeding. Serum bile acids were then measured by enzymatic assay from these samples. Complete blood counts and serum chemistry profiles were also performed to rule out the presence of concurrent hepatic disease. Due to the effect of hemolysis, lipemia and icterus on the measurement of SBA, indices for these serum characteristics were measured.

Mean SBA levels measured were as follows:

Although the sample size is limited and further studies are warranted, this data suggests that SBA measures in dolphins are similar to those of small domestic animals and that they follow a similar temporal pattern of reabsorption from the bloodstream. It is suggested that SBA can be routinely utilized as a measure of hepatic function in suspected hepatopathies in cetaceans. As with small domestic animals the recommended protocol would involve obtaining a blood sample following a twelve hour fast, and obtaining a second sample two hours post-prandially.

References

1.  John G. Shedd Aquarium, 1200 S. Lake Shore Drive Chicago, IL 60605

2.  University of Missouri, Columbia Missouri, 65211

3.  University of Illinois at Urbana-Champaign, 2001 S. Lincoln Avenue, Urbana, Il 61801