Quantification of hepatic and renal cortical echogenicity in clinically normal cats

Objective-To quantitatively determine echogenicity of the liver and renal c ortex in clinically normal cats. Animals-17 clinically normal adult cats. Procedure-3 ultrasonographic images of the liver and the right kidney were digitized from video output from each cat. Without changing the ultrasound machine settings, an image of a tissue-equivalent phantom was digitized. Bi opsy specimens of the right renal cortex and fiver were obtained far histol ogic examination. Mean pixel intensities within the region of interest (ROI ) on hepatic, renal cortical, and tissue-equivalent phantom ultrasonographi c images were determined by histogram analysis. From ultrasonographic image s, mean pixel intensities for hepatic and renal cortical ROI were standardi zed by dividing each mean value by the mean pixel intensity from the tissue -equivalent phantom. Results-The mean (+/- SD) standardized hepatic echogenicity Value was 1.06 +/- 0.02 (95% confidence interval, 1.02 to 1.10). The mean standardized rig ht renal cortical echogenicity value was 1.04 +/- 0.02 (95% confidence inte rval, 1.01 to 1.08). The mean combined standardized hepatic and renal corti cal echogenicity value was 1.02 +/- 0.05 (95% confidence interval, 0.99 to 1.04). Conclusions and Clinical Relevance-Quantitative determination of hepatic an d renal cortical echogenicity in cats is feasible, using histogram analysis , and may be useful for early detection of diffuse parenchymal disease and for serially evaluating disease progression.