Transient Hepatic Attenuation Difference (THAD) or Fat Sparing? Aberrant Right Gastric Vein (ARGV) Determining a Pseudolesion at the Border of the IInd/IIIrd Liver Segments. Review of Developmental Concepts

The aberrant right gastric vein (ARGV) is a rare anatomical variation. It can be responsible for unexplained hyperdensities in the hepatic parenchyma on CT scans, also known as third inflow effects. We present two cases sharing similar vascular pattern and slightly different imagistic findings on ultrasound and computer-tomography performed studies. Both ultrasonographies showed a nodular-geographic hypoechoic area within a hyperechogenic fatty liver. Further CT evaluation showed in both cases a hyperattenuating homogenous area clearly visible on all four phases at the border of the IInd/IIIrd hepatic segment, that enhance especially on the portal venous phase, with no slow-fill, wash-out, central scar or rim-like features. The areas were considered to be focal fat sparing areas in diffuse fatty liver or a perfusion disorder due to the presence of an aberrant right gastric vein. The aim of this paper is to discuss the embryological aspects which are the groundwork for this vascular anomaly and to correlate the findings with imagistic aspects. These two ARGV produced pseudolesions, understood as focal fat sparing areas within diffuse fatty livers. These pseudolesions mimic liver tumours, therefore it is important to look for such an aberrant vessel in order to rule out other diagnoses.