An assessment of the utility and repeatability of the renal resistive index in horses.
Authors: Siwinska Natalia, Zak Agnieszka, Slowikowska Malwina, Szczepankiewicz Barbara, Niedzwiedz Artur, Paslawska Urszula
Journal: PloS one
Summary
# Editorial Summary: Renal Resistive Index in Horses Establishing reference values for renal resistive index (RI) measurement via Doppler ultrasonography is clinically important for detecting vascular compromise in equine kidneys, yet normative data across age groups remains limited. Polish researchers examined intrarenal arterial RI in 45 warmblood horses (15 foals, 15 adults, 15 elderly) using pulsed-wave Doppler on standing, unsedated animals, with measurements repeated two hours later to assess reproducibility. Mean RI values were 0.48 ± 0.05 (left kidney) and 0.49 ± 0.05 (right kidney), with no significant difference between foals and adults, though elderly horses demonstrated significantly elevated RI—a finding likely reflecting age-related vascular stiffening. Pulse pressure emerged as the only physiological variable influencing RI measurements, whilst the technique showed high repeatability (coefficients of 0.089–0.09), indicating that operator-dependent variation is minimal once proficiency is achieved. Whilst these findings provide a useful baseline for clinical interpretation and suggest the measurement is reproducible, practitioners should account for patient age and systemic haemodynamics when evaluating RI values, and recognise that the procedure demands considerable technical skill and time investment to perform reliably.
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Practical Takeaways
- •When using renal resistive index as a diagnostic tool, establish age-specific reference values as elderly horses normally have higher RI than younger animals
- •Account for patient pulse pressure when interpreting RI measurements, as this physiological parameter significantly influences results
- •Understand that while the measurement is repeatable, it requires substantial technical skill and time investment—consider training and workflow implications before implementing in practice
Key Findings
- •Mean renal resistive index was 0.48±0.05 (left kidney) and 0.49±0.05 (right kidney) in healthy warmblood horses
- •Elderly horses had significantly higher RI values compared to foals and adult horses
- •Pulse pressure was the only physiological parameter significantly affecting RI values
- •Measurement repeatability was high (coefficient 0.089-0.09) but procedure is time-consuming and requires operator experience