Riedel lobe is an common anatomical variant of the liver to be aware of because it can simulate a mass.
Its misidentification as a pathologic abdominal mass has lead to laparotomy. Pathology can also occur within it (e.g. malignancy or even torsion) and cause atypical liver symptoms low in the pelvis 2, 4.
Riedel lobe has an incidence of ~17.5% (range 3.3-31%) and is more frequently found in females 2-3 with a M:F of approximately 1:3 4.
Riedel lobe is a tongue-like, inferior projection of the right lobe of the liver beyond the level of the most inferior costal cartilage on cross-sectional images 1. It is not considered a true accessory lobe of the liver but an anatomical variant of the right lobe of the liver 3.
History and etymology
It was originally reported in 1888 by Riedel in seven female patients who had palpable masses in the right hypochondrium, which were subsequently confirmed at surgery 2.