Gray Scale Ultrasound, Color Doppler Ultrasound, and Contrast-Enhanced Ultrasound in Renal Parenchymal Diseases.

Ultrasound (US), which may be combination of gray scale and spectral Doppler US, color and power Doppler US, with or without microbubble contrast agents, is usually the first imaging modality to be used in renal parenchymal diseases. The most typical appearance of diffuse renal parenchymal diseases on gray scale US is an increased renal cortical echogenicity and increased or reduced corticomedullary differentiation. Spectral Doppler analysis of intrarenal flows may reveal an increase in intrarenal resistive index value greater than 0.70 in native kidneys, and greater than 0.8 in renal transplants. Gray scale US and spectral Doppler US do not exhibit high specificity and sensitivity because different renal parenchymal diseases often display the same US appearance, whereas the same renal parenchymal disease may present different appearances on US according to disease stage. Consequently, correlation of the US pattern with patient's history and clinical background is essential for a correct characterization.