Feasibility of non-enhanced CT for assessing longitudinal changes in hepatic steatosis

To evaluate the feasibility of computed tomography (CT) in the assessment of the change in hepatic steatosis (HS) in longitudinal follow-up by employing pathological HS as the reference standard. We retrospectively evaluated 38 living liver donor candidates (27 men and 11 women; mean age, 29.5 years) who underwent liver biopsy twice and had liver CT scans within 1 week of each biopsy. Four readers independently calculated CT(L-S) index by subtracting spleen attenuation from liver attenuation on non-enhanced CT images. The changes in pathological HS (ΔHS) and CT(L-S) (ΔCT(L-S)) between the 1st and 2nd examinations were assessed. The correlation between ΔHS and ΔCT(L-S) was assessed using the linear regression analysis. Inter-observer measurement error for ΔCT(L-S) among the 4 readers was assessed using the repeatability coefficient. ΔCT(L-S) showed a significant correlation with ΔHS in all readers (r = 0.571–0.65, P < .001). The inter-observer measurement error for ΔCT(L-S) was ±8.9. The ΔCT(L-S) values beyond the measurement error were associated with a consistent change in HS in 83.3% (13/15) to 100% (15/15), with sensitivities of 47.8 to 79.9% and specificities of 86.7 to 100% for detecting an absolute change of ≥10% in HS among the 4 readers. However, ΔCT(L-S) values within the measurement error were associated with a consistent change in HS in 43.5% (8/19) to 61.5% (16/26). The change in CT(L-S) roughly reflects the change in HS during longitudinal follow-up. A small change in CT(L-S) should not be considered meaningful, while a larger change in CT(L-S) beyond the measurement error strongly indicates a true change in HS.