Diagnostic Performance of MR Elastography for Liver Fibrosis in Children and Young Adults with a Spectrum of Liver Diseases.

Purpose To assess the diagnostic performance of magnetic resonance (MR) elastography-derived liver stiffness to detect liver fibrosis in a pediatric and young adult population with a spectrum of liver diseases. Materials and Methods This retrospective study included patients younger than 21 years of age who underwent MR elastography and liver biopsy within 3 months of one another between January 2012 and September 2016 for indications other than liver transplantation or Fontan palliation of congenital heart disease. MR elastography examinations were reprocessed by a single observer, blinded to pathologic findings. Pathology specimens were reviewed by a single pathologist who scored steatosis (lipid in ≥ 5% of hepatocytes) and staged fibrosis. Receiver operating characteristic (ROC) curves were used to assess diagnostic performance. Results A total of 86 patients, 49 (57%) male with a median age of 14.2 years (range, 0.3-20.6 years), were included. Fifty-one patients (59.3%) had Ludwig stage 2 or higher fibrosis; 44 patients (51.2%) had hepatic steatosis. The area under the ROC curve for Ludwig stage 0-1 versus stage 2 or higher fibrosis was 0.70 (95% confidence interval [CI]: 0.59, 0.81) for the whole population and was significantly lower for patients with steatosis versus those without (0.53 [95% CI: 0.35, 0.71] vs 0.82 [95% CI: 0.67, 0.96], P = .014). Optimal stiffness cut-offs for the entire population were 2.27 kPa with 68.6% sensitivity (95% CI: 57.2%, 80.1%) and 74.3% specificity (95% CI: 63.5%, 85.1%) or 1.67 kPa with 35.3% sensitivity (95% CI: 23.5%, 47.1%) and 91.4% specificity (95% CI: 84.5%, 98.3%). Conclusion In children and young adults, MR elastography performs significantly better for distinguishing stage 0-1 versus stage 2 or higher fibrosis in patients without steatosis than in those with steatosis. This suggests a confounding effect of steatosis or inflammation in the population with nonalcoholic fatty liver disease. RSNA, 2018.