Assessment of liver fat in an obese patient population using noncontrast CT fat percent index

Comparison of correlations between lipid profile and different computed tomography fatty liver criteria in the setting of incidentally noted fatty liver on computed tomography examinations

PURPOSE

The aim of this study was to compare the correlations between computed tomography (CT) criteria for hepatic steatosis and lipid profile values when hepatic steatosis is incidentally detected.

PARTICIPANTS AND METHODS

This is an institutional Review Board-approved, HIPPA-compliant, retrospective study of abdominal CT scans in 200 randomly selected patients who had either nonenhanced CT (NECT) or contrast-enhanced CT (CECT) studies with reported fatty liver. The participants were matched for age, sex, and ethnicity with 200 patients with nonfatty liver. For NECT, four different criteria have been proposed in the literature to diagnose fatty liver: (i) liver Hounsfield Units (HU) less than 48 HU, (ii) ratio of liver to spleen HU less than 0.8, (iii) HU difference between liver and spleen less than -10, and (iv) hepatic vessel HU greater than or equal to liver HU. For CECT, the criteria was attenuation difference between liver and spleen HU, in the portal venous phase of up to -20 to -25 HU. Laboratory results (low-density lipoprotein, high-density lipoprotein, triglycerides) were documented. Matched analyses and conditional logistic regression analysis were carried out for matched variables.

RESULTS

There were statistically significant differences in triglyceride values, between the cases and controls (P=0.02), when all criteria were considered. Also, statistically significant differences were found between cases and controls on the basis of NECT criterion 2 and high-density lipoprotein (P=0.04), as well as CECT criteria and triglyceride levels (P=0.02). In addition, the data indicate that criteria for steatosis on CECT may be more broad than traditionally utilized.

CONCLUSION

Incidental reporting of fatty liver on NECT/CECT should prompt consideration of clinical follow-up and lipid profile testing in an otherwise asymptomatic patient. Additional metrics for the diagnosis of steatosis in CECT exam should also be considered.

Quantification of liver fat: A comprehensive review

Fat accumulation in the liver causes metabolic diseases such as obesity, hypertension, diabetes or dyslipidemia by affecting insulin resistance, and increasing the risk of cardiac complications and cardiovascular disease mortality. Fatty liver diseases are often reversible in their early stage; therefore, there is a recognized need to detect their presence and to assess its severity to recognize fat-related functional abnormalities in the liver. This is crucial in evaluating living liver donors prior to transplantation because fat content in the liver can change liver regeneration in the recipient and donor. There are several methods to diagnose fatty liver, measure the amount of fat, and to classify and stage liver diseases (e.g. hepatic steatosis, steatohepatitis, fibrosis and cirrhosis): biopsy (the gold-standard procedure), clinical (medical physics based) and image analysis (semi or fully automated approaches). Liver biopsy has many drawbacks: it is invasive, inappropriate for monitoring (i.e., repeated evaluation), and assessment of steatosis is somewhat subjective. Qualitative biomarkers are mostly insufficient for accurate detection since fat has to be quantified by a varying threshold to measure disease severity. Therefore, a quantitative biomarker is required for detection of steatosis, accurate measurement of severity of diseases, clinical decision-making, prognosis and longitudinal monitoring of therapy. This study presents a comprehensive review of both clinical and automated image analysis based approaches to quantify liver fat and evaluate fatty liver diseases from different medical imaging modalities.