Magnetic resonance imaging findings in autoimmune hepatitis: how frequent and reproducible are they?

OBJECTIVE: To determine the frequency and interobserver reproducibility of the magnetic resonance imaging (MRI) features considered diagnostic for autoimmune hepatitis.

MATERIALS AND METHODS: Two abdominal radiologists, blinded to pathology data, reviewed the MRI examinations of 20 patients with autoimmune hepatitis, looking for liver enhancement, lymphadenopathy, portal hypertension, and chronic liver disease. The pattern of liver fibrosis was categorized as reticular, confluent, or mixed. Interobserver agreement was assessed by calculating intraclass correlation coefficients and kappa statistics.

RESULTS: The most common abnormal finding on MRI was surface nodularity (in 85%), followed by liver fibrosis with a reticular pattern (in 80%)-categorized as mild (in 25.0%), moderate (in 43.8%), or severe (in 31.2%)-; heterogeneous liver enhancement (in 65%); splenomegaly (in 60%); caudate lobe enlargement (in 50%); and lymphadenopathy (in 40%). The interobserver agreement was almost perfect for surface nodularity (0.83), ascites (0.89), and liver volume (0.95), whereas it was just slight and fair for the degree of fibrosis and for heterogeneous liver enhancement (0.12 and 0.25, respectively). It was also slight and fair for expanded gallbladder fossa and enlarged preportal space (0.14 and 0.36, respectively), both of which are indicative of chronic liver disease.

CONCLUSION: The interobserver agreement was satisfactory for surface nodularity (the most prevalent abnormal MRI finding), ascites, liver volume, and splenomegaly. Conversely, it was only slight or fair for common but less objective criteria.