QUALITATIVE ASSESSMENT OF LIVER FOR FATTY INFILTRATION ON CONTRAST-ENHANCED CT - IS MUSCLE A BETTER STANDARD OF REFERENCE THAN SPLEEN

Purpose: Our goal was to determine whether spleen or muscle can be use d as a qualitative standard of reference for diagnosing fatty infiltra tion of Liver on contrast-enhanced CT. Method: Qualitative visual comp arisons and quantitative region-of-interest measurements of liver, spl een, and muscle were made on scans of 96 patients who underwent dynami c CT before and after injection of intravenous contrast material. As t he standard of reference, the portion of liver assessed was considered fatty if its attenuation measured less than spleen on noncontrast CT. Results: In 16 (17%) scans, the portion of liver assessed was fatty o n noncontrast CT. After contrast material administration, the attenuat ion of that portion of liver measured less than splenic attenuation in 93 (97%) of 96 cases (including all 16 fatty livers). Only four (25%) fatty livers, and no nonfatty livers, were visually judged to be less attenuating than muscle after contrast material; these four were the most fatty shown on noncontrast CT. Comparing hepatic and splenic atte nuation on postcontrast CT resulted in a specificity of 30% and a posi tive predictive Value of 20%; comparing hepatic and muscle attenuation on postcontrast CT yielded corresponding values of 100 and 100% but a sensitivity of 25%. Conclusion: For the visual assessment of fatty li ver, spleen is not an accurate reference standard on contrast-enhanced CT. However, fatty liver can be diagnosed on contrast-enhanced CT if liver appears less attenuating than muscle-a situation that occurs onl y if fatty infiltration is pronounced.