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

Background & Aims: Liver 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 (¹H-MRS) and histology. Methods: We recruited 146 patients and performed: a liver US using a 5-parameter scoring system, a liver ¹H-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 18 months of follow-up. Results: The performance of liver US (parenchymal echo alone) was rather modest, and significantly worse than ¹H-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 ¹H-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 ¹H-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. Conclusions: Despite 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.