Transcutaneous ultrasonography for visualization of the kidneys in captive Asian elephants (Elephas maximus): a quantitative assessment of echogenicity and echotexture in comparison with the liver and spleen

Abstract

Background: Kidney transcutaneous ultrasonography can be used to assess renal condition and is less invasive than transrectal ultrasonography, which typically requires intensive restraint, sedation, or general anesthesia. To date, this less invasive technique has not been evaluated in Asian elephants (Elephas maximus). The gray level histogram technique associated with transcutaneous ultrasonography is a quantitative approach to objectively measure echogenicity and echotexture. This study utilized gray-level histograms (GLH) to assess echogenicity and echotexture of the kidneys, spleen, and liver of 49 captive Asian elephants via transcutaneous ultrasonography, to obtain a baseline for healthy animals and to compare various internal organs as a reference for quantitative analyses. Results: Retroperitoneal fat was the most hyperechoic region identified, followed by the spleen. The renal medullas and the left cortex were the three most homogenous tissues. No significant differences were found between the sexes or age groups. Conclusions: This study found that transcutaneous ultrasonography could be used to quantitatively measure echogenicity and echotexture in captive Asian elephants using the GLH technique. Baseline GLH references were developed for healthy captive Asian elephants for renal, hepatic and splenic transcutaneous ultrasonography.