Same Results, Different Routes: Renal Doppler Indexes Consistent in Equine Ultrasound Approaches

Resistivity and Pulsatility Indexes Renal Values Do Not Differ When Obtained from Abdominal or Transrectal Approaches in Healthy Horses

Nathalia dos Santos Rosse, Rachel de Andrade Tavares, Maria Clara Nunes, Bruna Waddington de Freitas, Emily Correna Carlo Reis

Background
Doppler ultrasonography provides valuable insight into renal hemodynamics by measuring resistivity index (RI) and pulsatility index (PI), which reflect vascular compliance and potential renal injury. In horses, both transabdominal (TA) and transrectal (TR) approaches are used for renal imaging, but their equivalency in Doppler measurements has not been confirmed. This study aimed to determine whether renal RI and PI values differ based on the ultrasound approach and kidney side in healthy horses.

Methods
Twenty-nine healthy adult horses from multiple breeds and facilities underwent renal Doppler ultrasonography using both TA and TR approaches. RI and PI were measured in the arcuate or interlobar arteries of both kidneys. Statistical comparisons between techniques and kidney sides were performed using two-way ANOVA. Ultrasound image quality and operator challenges were documented, and all exams were conducted without sedation.

Results
Mean RI and PI values for the left kidney were similar across both techniques (TA RI: 0.545, PI: 0.864; TR RI: 0.554, PI: 0.877). Right kidney values also showed close agreement (TA RI: 0.568, PI: 0.934; TR RI: 0.557, PI: 0.872). No statistically significant differences were found between sides or approaches for either RI or PI. However, acquiring satisfactory TR waveforms for the right kidney was more difficult, particularly in large horses. Overall, image quality for the left kidney was better via TR, while TA was more effective for the right kidney.

Limitations
The study did not measure systemic blood pressure, which could influence RI/PI values. Image acquisition success varied due to anatomical and animal size differences. Additionally, urine was not collected for correlative renal evaluation, and fewer complete datasets were obtained for right kidneys via TR due to access limitations.

Conclusions
Renal Doppler indexes (RI and PI) obtained via transabdominal and transrectal ultrasonography are statistically equivalent in healthy horses. Despite anatomical challenges, both techniques are valid for assessing renal perfusion. These findings support flexibility in clinical approach selection, guided by horse size and kidney accessibility. Further studies are needed to validate these indexes in horses with renal disease.

Disclaimer: The summary generated in this email was created by an AI large language model. Therefore errors may occur. Reading the article is the best way to understand the scholarly work. The figure presented here remains the property of the publisher or author and subject to the applicable copyright agreement. It is reproduced here as an educational work. If you have any questions or concerns about the work presented here, reply to this email.