Biopsy-proven Nonsteatotic Liver in Adults: Estimation of Reference Range for Difference in Attenuation between the Liver and the Spleen at Nonenhanced CT

Purpose: To establish the reference range for hepatic attenuation minus splenic attenuation difference (CTL-S) values on nonenhanced computed tomographic (CT) images obtained in adults with a biopsy-proved nonsteatotic liver and determine the CTL-S criterion for diagnosing hepatic steatosis. Materials and Methods: This retrospective study was institutional review board approved, and all subjects had provided written informed consent. The CTL-S was measured in 315 liver donor candidates (207 men, 108 women; mean age, 31.5 years +/- 10.1 [standard deviation]) who underwent nonenhanced CT of the liver and subsequent ultrasonographically guided liver biopsy on the same day. Nonenhanced liver CT was performed with a 16-section multidetector scanner in 154 individuals and with a 64-section multidetector scanner in 161 individuals. Biopsy specimens were analyzed for degree of hepatic steatosis and iron deposition. The CTL-S reference range was determined according to Clinical and Laboratory Standards Institute guideline C28-A3 in individuals with a histologically proved nonsteatotic liver. The sensitivity of nonenhanced CT for the diagnosis of 5% or greater and 30% or greater hepatic steatosis with use of the lower limit of the reference range as the diagnostic cutoff was determined. The effects of subject age and sex, CT scanner type, and hepatic iron on the CTL-S were evaluated by using multiple linear regression analysis. Results: Ninety-six subjects (48 men, 48 women) were found to have a histologically proved nonsteatotic liver, with an estimated reference range for CTL-S values of 1-18 HU. With a CTL-S of less than 1 HU as the criterion for hepatic steatosis, the sensitivities of nonenhanced CT for 5% or greater and 30% or greater hepatic steatosis were 18.6% (29 of 156 subjects) and 67 % (26 of 39 subjects), respectively. Subject age had a significant but negligible effect on CT L 2 S (0.076-HU increase per year of age, P = .009), subject sex and scanner type had no effects on CTL-S, and hepatic iron deposition significantly increased the CTL-S (1.434-HU increase per increase in iron deposition grade, P = .011). Conclusion: The histologically proved reference range of CTL-S values for nonsteatotic livers was 1-18 HU. A CTL-S of less than 1 HU could be used as a conservative criterion for diagnosing hepatic steatosis with nonenhanced CT more consistently. (C)RSNA, 2011