Clinical value of liver ultrasound for the diagnosis of nonalcoholic fatty liver disease in overweight and obese patients

Background & AimsLiver ultrasound (US) is usually used in the clinical setting for the diagnosis and follow-up of patients with nonalcoholic fatty liver disease (NAFLD). However, no large study has carefully assessed its performance using a semiquantitative ultrasonographic scoring system in overweight/obese patients, in comparison to magnetic resonance spectroscopy (H-1-MRS) and histology. MethodsWe recruited 146 patients and performed: a liver US using a 5-parameter scoring system, a liver H-1-MRS to quantify liver fat content, and a liver biopsy to assess histology. All measurements were repeated in a subgroup of patients (n=62) after 18months of follow-up. ResultsThe performance of liver US (parenchymal echo alone) was rather modest, and significantly worse than H-1-MRS (AUROC: 0.82 [0.69-0.94] vs. 0.96 [0.90-1.00]; P=0.04). However, the AUROC improved when different echographic parameters were taken into account (AUROC: 0.89 [0.83-0.96], P=0.15 against H-1-MRS). Optimum sensitivity for liver US was achieved at a liver fat content 12.5%, suggesting that below this threshold, liver US is less sensitive. Liver H-1-MRS showed a high accuracy for the diagnosis of NAFLD, and correlated strongly with histological steatosis (r=0.73, P<0.0001). None of the imaging tests was adequate enough to predict changes over time in histology. ConclusionsDespite its widespread use, liver US has several important limitations that healthcare providers should recognize, particularly because of its low sensitivity. Using a combination of echographic parameters, liver US showed a significant improvement in its diagnostic performance, but still was of limited value for monitoring treatment over time.