Ultrasonographical diagnosis of fatty liver: significance of the liver-kidney contrast.

In order to investigate the reliability of ultrasonography in the diagnosis of fatty liver, retrospective evaluation was made of abdominal echograms in 45 patients with various diffuse liver diseases who underwent liver biopsy within 2 weeks after the ultrasound study. Instead of the well-recognized but subjective diagnostic criterion, i.e. the bright liver pattern, liver-kidney contrast is proposed as a new criterion. The liver-kidney contrast is based on the brightness of the liver in comparison to the renal parenchyma where fatty change seldom occurs. Combination of this liver-kidney contrast with two other well-known ultrasonographical findings of fatty liver, vascular blurring and deep attenuation, enables us to grade fatty change semiquantitatively. When fatty change of over 30% in the hepatic lobule was adopted as the definition of fatty liver, the satisfaction of both liver-kidney contrast and vascular blurring presented an ultrasound diagnostic criterion for fatty liver, with sensitivity of 83%, specificity of 100%, and an accuracy of 96%.