Serum bile acids concentrations in healthy and clinically ill neonatal foals.
Authors: Barton Michelle Henry, LeRoy Bruce E
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Serum Bile Acids in Neonatal Foals Establishing accurate reference ranges for neonatal foals is crucial for distinguishing normal physiological variation from genuine hepatic dysfunction, yet most clinicians rely on adult horse values when interpreting laboratory results in young stock. Henry and Barton's 2007 prospective study compared serum bile acid (SBA) concentrations across three groups—10 healthy mature horses, 12 healthy neonates sampled serially from birth through 6 weeks of age, and 31 clinically ill foals under one month old—to determine whether age-specific thresholds were necessary. A significant negative correlation emerged between age and SBA concentration; critically, healthy foals demonstrated markedly elevated SBA values at every timepoint compared with mature horses, yet ill foals showed no significant difference from age-matched healthy counterparts, suggesting that elevated SBA alone cannot diagnose primary hepatic disease in this population. The authors noted that enzymatic assay methods produced higher SBA values than radioimmunoassay, with measurement bias increasing at higher concentrations, emphasising the importance of standardised methodology in establishing reference ranges. For equine practitioners, these findings underscore that adult reference ranges are inappropriate for neonatal assessment and highlight the need for age-matched interpretation windows—particularly the first 6 weeks of life—when evaluating neonatal foal pathology, whilst elevated SBA without concurrent SDH elevation or clinical signs may represent normal neonatal physiology rather than significant organ compromise.
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Practical Takeaways
- •Use age-specific reference ranges for serum bile acids in neonatal foals rather than adult reference ranges to avoid misinterpretation of elevated but physiologically normal values
- •Elevated SBA alone should not be used as a diagnostic indicator of hepatic disease in neonates—clinical signs and other parameters must be considered
- •Be aware that the measurement method (enzymatic vs radioimmunoassay) significantly affects SBA values and consistency in methodology is important for interpretation
Key Findings
- •Serum bile acids concentrations are significantly higher in healthy neonates compared to mature horses across the first 6 weeks of life
- •There was a significant negative correlation between age and SBA concentration in foals
- •No significant differences in SBA concentrations between age-matched healthy and clinically ill foals, despite illness generally elevating SBA
- •Radioimmunoassay values were systematically lower than enzymatic SBA values, with increasing bias at higher concentrations