Early detection of nonalcoholic steatohepatitis in patients with nonalcoholic fatty liver disease by using MR elastography

Abstract

Purpose: To investigate the diagnostic accuracy (area under the receiver operating characteristic curve [AUROC]) of magnetic resonance (MR) elastography for the early detection of nonalcoholic steatohepatitis (NASH) among patients with nonalcoholic fatty liver disease (NAFLD).

Materials and methods: An institutional review board-approved and HIPAA-compliant retrospective study was conducted in 58 NAFLD patients. Informed consent was waived by the review board. Hepatic stiffness, relative fat fraction, inflammation grade, and fibrosis stage were assessed from MR elastography, in-phase and out-of-phase gradient-echo imaging, and liver biopsy histopathologic review, respectively. Pairwise t testing, receiver operating characteristic analysis, and partial correlation analysis were performed.

Results: The mean hepatic stiffness for patients with simple steatosis (2.51 kPa) was less (P = .028) than that for patients with inflammation but no fibrosis (3.24 kPa). The mean hepatic stiffness for patients with inflammation but no fibrosis was less (P = .030) than that for patients with hepatic fibrosis (4.16 kPa). Liver stiffness had high accuracy (AUROC = 0.93) for discriminating patients with NASH from those with simple steatosis, with a sensitivity of 94% and a specificity 73% by using a threshold of 2.74 kPa.

Conclusion: In patients with NAFLD, hepatic stiffness measurements with MR elastography can help identify individuals with steatohepatitis, even before the onset of fibrosis; NAFLD patients with inflammation but no fibrosis have greater liver stiffness than those with simple steatosis and lower mean stiffness than those with fibrosis.

RSNA, 2011

Figures

Figure 1a:

MR elastography magnitude images (top row) and MR elastograms (bottom row) in NAFLD patients with (a, d) simple steatosis, (b, e) inflammation but no fibrosis, and (c, f) fibrosis. The mean liver stiffness was 2.02, 3.59, and 7.52 kPa, respectively.

Figure 1b:

MR elastography magnitude images (top row) and MR elastograms (bottom row) in NAFLD patients with (a, d) simple steatosis, (b, e) inflammation but no fibrosis, and (c, f) fibrosis. The mean liver stiffness was 2.02, 3.59, and 7.52 kPa, respectively.

Figure 1c:

MR elastography magnitude images (top row) and MR elastograms (bottom row) in NAFLD patients with (a, d) simple steatosis, (b, e) inflammation but no fibrosis, and (c, f) fibrosis. The mean liver stiffness was 2.02, 3.59, and 7.52 kPa, respectively.

Figure 1d:

MR elastography magnitude images (top row) and MR elastograms (bottom row) in NAFLD patients with (a, d) simple steatosis, (b, e) inflammation but no fibrosis, and (c, f) fibrosis. The mean liver stiffness was 2.02, 3.59, and 7.52 kPa, respectively.

Figure 1e:

MR elastography magnitude images (top row) and MR elastograms (bottom row) in NAFLD patients with (a, d) simple steatosis, (b, e) inflammation but no fibrosis, and (c, f) fibrosis. The mean liver stiffness was 2.02, 3.59, and 7.52 kPa, respectively.

Figure 1f:

MR elastography magnitude images (top row) and MR elastograms (bottom row) in NAFLD patients with (a, d) simple steatosis, (b, e) inflammation but no fibrosis, and (c, f) fibrosis. The mean liver stiffness was 2.02, 3.59, and 7.52 kPa, respectively.

Figure 2:

Mean hepatic stiffness for the three NAFLD patient groups on a logarithmic scale. Stiffness was significantly greater in group I than in group S (P = .028), and was significantly greater in group F than in group I (P = .030). F = fibrosis, I = inflammation without fibrosis, S = simple steatosis.

Figure 3:

Receiver operating characteristic analysis shows performance of MR elastography–measured liver stiffness for differentiating NASH from simple steatosis. The graph indicates a high diagnostic accuracy with an AUROC of 0.93.

Figure 4:

Mean RFF for the three NAFLD patient groups on a logarithmic scale. No significant differences were found (P > .05). F = fibrosis, I = inflammation without fibrosis, S = simple steatosis.