Hepatic steatosis (fatty liver disease) in asymptomatic adults identified by unenhanced low-dose CT.
OBJECTIVE
The purpose of this study was to investigate the prevalence of hepatic steatosis in an asymptomatic U.S. adult population using attenuation values at unenhanced CT as the reference standard. We also assessed the utility of known clinical risk factors for diagnosis.


METHODS
For 3,357 consecutive asymptomatic adults (1,865 women and 1,492 men; mean age, 57.0 years), hepatic and splenic CT attenuation values (Hounsfield units) were obtained by unenhanced CT using a low-dose colonography technique for colorectal cancer screening. Multiple attenuation criteria for steatosis were applied, including liver thresholds and comparison of liver and spleen attenuation. Relevant clinical risk factors were compared against a CT liver attenuation < or = 40 HU, which has been shown to exclude mild steatosis.


RESULTS
Mean liver attenuation was 58.8 +/- 10.8 (SD) HU. The prevalence of moderate-to-severe hepatic steatosis (defined by liver attenuation < or = 40 HU) was 6.2% (208/3,357). For CT attenuation criteria that include milder degrees of steatosis, prevalence increased to as high as 45.9% (1,542/3,357) for a liver-to-spleen attenuation ratio of < or = 1.1. Overweight status (body mass index > 25) was a sensitive indicator for moderate-to-severe steatosis (92.8%) but was highly nonspecific (37.5%). Other clinical risk factors, such as diabetes, dyslipidemia, hypertension, alcohol overuse, and hepatitis, were more specific (77.6-92.4%) but highly insensitive (1.9-37.5%). Combining clinical risk factors did not substantially increase the accuracy for screening.


CONCLUSIONS
Assessment of liver attenuation by use of unenhanced CT represents an objective and noninvasive means for detection of asymptomatic hepatic steatosis, whereas clinical risk factor assessment is unreliable. Further longitudinal investigation is needed to determine the most appropriate attenuation threshold and the risk for disease progression to steatohepatitis and cirrhosis.
Boyce
Cody J
CJ
Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Science Center, 600 Highland Ave., Madison, WI 53792-3252, USA.
Pickhardt
Perry J
PJ
Kim
David H
DH
Taylor
Andrew J
AJ
Winter
Thomas C
TC
Bruce
Richard J
RJ
Lindstrom
Mary J
MJ
Hinshaw
J Louis
JL
D005234:Fatty Liver / Q000000981:diagnostic imaging* / Q000453:epidemiology; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D012372:ROC Curve; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D012307:Risk Factors; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*