title: Longitudinal Changes in Liver Fat Content in Asymptomatic Adults: Hepatic Attenuation on Unenhanced CT as an Imaging Biomarker for Steatosis.
abstract: OBJECTIVE
  The objective of this study was to evaluate changes in liver fat content over time in asymptomatic adults and to investigate the factors that may influence these changes.
  
  
  METHODS
  Liver attenuation on unenhanced CT images of 1022 asymptomatic adults (556 women and 466 men; mean age at the time of the index CT examination, 56.7 years) was retrospectively measured on initial and surveillance CT colonography screening examinations (mean [± SD] interval, 5.5 ± 0.8 years). Changes in liver attenuation (expressed as Hounsfield units) were assessed according to various factors, including body mass index (BMI), age, and sex.
  
  
  RESULTS
  Mean liver attenuation was 60.3 HU on the index CT scan and 58.4 HU on the 5-year follow-up CT scan (p < 0.0001). Changes in liver attenuation greater than 10 HU, 5-10 HU, and less than 5 HU were observed in 187 (18%), 212 (21%), and 623 (61%) individuals, respectively. Changes in attenuation greater than 10 HU were negative (i.e., fattier liver) in 130 of 187 individuals (70%) and were more likely to be associated with an increase in BMI (83 of 130 individuals [64%] vs 19 of 57 individuals [33%]; p < 0.0001). For changes in attenuation of 5 HU or more, negative (steatotic) changes outnumbered positive changes, occurring in 258 of 1022 individuals (25%) versus 141 of 1022 individuals (14%) (p < 0.0001). Changes in BMI were negatively correlated with changes in attenuation (p = 0.015). There was no statistically significant correlation between changes in attenuation and either age or sex. An improved lipid profile and the use of a lipid-lowering medication regimen correlated with an interval decrease in liver attenuation.
  
  
  CONCLUSIONS
  Changes in liver attenuation over time, reflecting temporal changes in fat content, were quite variable in this asymptomatic adult population and were only partially explained by the factors examined. These observations may provide early insight into the natural history of incidental hepatic steatosis in asymptomatic adults.
authors.affiliation: 1 All authors: Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Science Center, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Luke
authors.initials: L
authors.lastname: Hahn
authors.affiliation: 1 All authors: Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Science Center, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Scott B
authors.initials: SB
authors.lastname: Reeder
authors.affiliation: 1 All authors: Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Science Center, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Muñoz del Rio
authors.affiliation: 1 All authors: Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Science Center, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Perry J
authors.initials: PJ
authors.lastname: Pickhardt
mesh_terms: D000368:Aged; D015415:Biomarkers; D018450:Disease Progression; D005234:Fatty Liver / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D015415:Biomarkers
keywords: CT; fatty liver; nonalcoholic fatty liver disease; nonalcoholic steatohepatitis; steatosis