Accessory fissures of the liver: CT and sonographic appearance.

Invaginations of the liver by the diaphragm form accessory fissures that may mimic the major hepatic fissures on sectional images. Accessory fissures are most common in the superior right hepatic lobe. Their average incidence on computed tomographic (CT) scans is 25%. Their frequency increases with age, approaching 70% in the seventh and eighth decades. Their depth may equal or exceed 2 cm in one-third of cases. Multiple accessory fissures may mimic pathologic liver nodules on CT and may be associated with diaphragmatic scalloping or eventration on the chest film. When only parts of these fissures are seen sonographically, they may be mistaken for echogenic liver lesions. The differentiation of accessory fissures from the major hepatic fissures, from pathologic lesions, and from sonographic pseudofissure artifacts is discussed.