Ultrasonography is a widely accessible imaging technique for the detection of fatty liver, but the reported accuracy and reliability have been inconsistent across studies. We aimed to perform a systematic review and meta-analysis of the diagnostic accuracy and reliability of ultrasonography for the detection of fatty liver. We used MEDLINE and Embase from October 1967 to March 2010. Studies that provided cross-tabulations of ultrasonography versus histology or standard imaging techniques, or that provided reliability data for ultra-sonography, were included. Study variables were independently abstracted by three reviewers and double checked by one reviewer. Forty-nine (4720 participants) studies were included for the meta-analysis of diagnostic accuracy. The overall sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of ultrasound for the detection of moderate-severe fatty liver, compared to histology (gold standard), were 84.8% (95% confidence interval: 79.5-88.9), 93.6% (87.2-97.0), 13.3 (6.4-27.6), and 0.16 (0.12-0.22), respectively. The area under the summary receiving operating characteristics curve was 0.93 (0.91-0.95). Reliability of ultrasound for the detection of fatty liver showed kappa statistics ranging from 0.54 to 0.92 for intrarater reliability and from 0.44 to 1.00 for interrater reliability. Sensitivity and specificity of ultrasound was similar to that of other imaging techniques (i.e., computed tomography or magnetic resonance imaging). Statistical heterogeneity was present even after stratification for multiple clinically relevant characteristics. Conclusion Ultrasonography allows for reliable and accurate detection of moderate-severe fatty liver, compared to histology. Because of its low cost, safety, and accessibility, ultrasound is likely the imaging technique of choice for screening for fatty liver in clinical and population settings.

Previous estimates of the prevalence of nonalcoholic fatty liver disease (NAFLD) in the US population relied on measures of liver enzymes, potentially underestimating the burden of this disease. We used ultrasonography data from 12,454 adults who participated in the Third National Health and Nutrition Examination Survey, conducted in the United States from 1988 to 1994. We defined NAFLD as the presence of hepatic steatosis on ultrasonography in the absence of elevated alcohol consumption. In the US population, the rates of prevalence of hepatic steatosis and NAFLD were 21.4% and 19.0%, respectively, corresponding to estimates of 32.5 (95% confidence interval: 29.9, 35.0) million adults with hepatic steatosis and 28.8 (95% confidence interval: 26.6, 31.2) million adults with NAFLD nationwide. After adjustment for age, income, education, body mass index (weight (kg)/height (m)²), and diabetes status, NAFLD was more common in Mexican Americans (24.1%) compared with non-Hispanic whites (17.8%) and non-Hispanic blacks (13.5%) (P = 0.001) and in men (20.2%) compared with women (15.8%) (P < 0.001). Hepatic steatosis and NAFLD were also independently associated with diabetes, with insulin resistance among people without diabetes, with dyslipidemia, and with obesity. Our results extend previous national estimates of the prevalence of NAFLD in the US population and highlight the burden of this disease. Men, Mexican Americans, and people with diabetes and obesity are the most affected groups.

Objective To evaluate the association between non-alcoholic fatty liver disease and all cause and cause specific mortality in a representative sample of the US general population.Design Prospective cohort study.