Yang Shin Park, MD Seong Ho Park, MD Seung Soo Lee, MD DaeYoon Kim.MD Yong Moon Shin, MD Woochang Lee, MD Sung-Gyu Lee, MD Eun Sil Yu, MD
Purpose: To establish the reference range for hepatic attenuation minus splenic attenuation difference (CTL_S) values on non-enhanced computed tomographic (CT) images obtained in adults with a biopsy-proved nonsteatotic liver and deter-mine 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 steato-sis, 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 CTL_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 in-crease per increase in iron deposition grade, P = .011).
Conclusion: The histologically proved reference range of CTL_S val-ues 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.