This is a middle aged woman complaining of continuous elevated liver enzymes. Her laboratory work up revealed elevated liver enzymes, negative hepatitis markers, elevated IgG, and smooth muscle autoantibodies (SMA) which were suggestive of autoimmune hepatitis. CT and MRI revealed liver cirrhosis with multiple lesions of fat density and signal on CT and MRI impressuve of hepatic steatosis, patchy lesions of contrast enhancement with no contrast wash out on the delayed phase, suggestive of inflammatory lesions, as well as indirect signs of hepatic fibrosis such as surface nodularity, ascites and widened preportal and gallbladder fossae.
Autoimmune hepatitis is usually diagnosed by biopsy, however, imaging might demonstrate characteristic features that may be helpful to distinguish this disease.
Autoimmune hepatitis is more common in women.
Autoimmune liver diseases are classified into:
- autoimmune hepatitis (AIH)
- primary sclerosing cholangitis (PSC)
- primary biliary cirrhosis (PBC)
Autoimmune hepatitis should be differentiated from viral hepatitis, alcoholic hepatitis and non-alcoholic fatty liver disease.
Diagnostic criteria of autoimmune hepatitis include:
- elevated antinuclear antibodies,antismooth muscle antibodies
- globulin level of more than 20 g/L
- coexistence of non-hepatic autoimmune diseases, including autoimmune thyroiditis, rheumatoid arthritis, and systemic lupus
- the elimination of other forms of hepatitis such as viral or toxic hepatitis
- histologic examination findings consistent with AIH
Radiographic features of autoimmune hepatitis include:
- hepatic steatosis is evident by lesions of low attenuation (<10 HU attenuation in the non-contrast phase and <25 HU in the portal venous phase). On MRI lesions appear of low signal on fat sat sequences and On T1 dual-echo sequence, the signal intensity on the out-of-phase sequence is reduced by >20% as compared to the in-phase sequences
- fibrosis manifested as reticular or confluent areas of delayed enhancement
- presence of porta-hepatis and portocaval lymph nodes
- intra-hepatic biliary radicle dilatation mainly in the overlap syndrome, autoimmune hepatitis, and primary sclerosing cholangitis are the most common overlap syndrome
- heterogeneous parenchymal enhancement which could be patchy, reticular, segmental, or lobar
- patchy early enhancement after contrast administration has been attributed to recent hepatocellular damage and intense inflammatory infiltrates
- fibrotic stage: evident by ascites, expanded gallbladder fossa, spleen size, and enlarged preportal space.