The effect of the skin-liver capsule distance on the accuracy of ultrasound diagnosis for liver steatosis and fibrosis

Purpose Transient elastography (TE) and the controlled attenuation parameter (CAP) have been used for diagnosis of liver fibrosis and steatosis. Obesity is a limiting factor to the accuracy of elastography; however, an XL probe was validated for use in obese patients. Two-dimensional shear wave elastography (2D-SWE) and attenuation imaging (ATI) have also been developed. It is unknown if obesity affects 2D-SWE/ATI values for evaluation of liver fibrosis and steatosis. We assessed the reliability of the measurement rate and the diagnostic performance of TE/CAP versus SWE/ATI. Methods The patients (n = 85) underwent TE/CAP, 2D-SWE/ATI, and liver biopsy on the same day. They were diagnosed with chronic hepatitis based on liver biopsy. The patients were divided into three groups by skin-liver capsule distance (SCD). Results The reliability of the measurement rate for the M probe was lower than that for the XL probe in the group with SCD over 22.5 mm. The rate achieved with 2D-SWE was high in all groups regardless of the SCD. In the assessment of the diagnostic performance, there was no difference between the area under the receiver-operating curve (AUROC) of TE compared to 2D-SWE to stratify the fibrosis stage. There was no difference in the AUROC for the stratification of the steatosis grades between CAP and ATI. The diagnostic accuracy of TE for F >= 3 fibrosis evaluated with the M probe and 2D-SWE was lower than that of TE evaluated with the XL probe in the group with SCD over 22.5 mm. Conclusion The ability of 2D-SWE to stratify fibrosis stage and steatosis grade was as good as FibroScan. However, 2D-SWE had a high reliability in the measurement rate regardless of the SCD with one probe. And the XL probe showed high diagnostic accuracy for severe fibrosis in the group with SCD over 22.5 mm.