Imaging description

Localized fat collection adjacent to the intrahepatic inferior vena cava is an uncommon incidental benign finding on CT. It is usually seen as a round (Figure 90.1) or oval (Figure 90.2) fat collection on axial CT. It is located at or above the level of the confluence of the hepatic veins and the inferior vena cava, and usually medial or anterior to the inferior vena cava, but can be seen posterior to the inferior vena cava. It demonstrates apparent fat attenuation on CT. On axial images, it may mimic a fat-containing lesion within the lumen of the inferior vena cava because of the acute angle of the fat collection with respect to the wall of the inferior vena cava. The right diaphragmatic crus forming a thin line medial to the fat collection may resemble the medial wall of the inferior vena cava on axial image (Figure 90.1).

Importance

Pericaval fat collection adjacent to the intrahepatic inferior vena cava represents a partial volume artifact of pericaval fat above the caudate lobe rather than true intraluminal lesion, and is usually of no clinical significance. However, it can be misdiagnosed as a mass in the inferior vena cava. Therefore, it is important not to misinterpret this finding as an abnormality of the inferior vena cava, such as thrombus or tumor.

Typical clinical scenario

The prevalence of pericaval fat collection near the intrahepatic inferior vena cava is considered rare, and this finding occurred in 0.5–0.55% in large CT studies. In patients with chronic liver disease, it is more commonly seen. Gibo et al. reported that pericaval fat collection was seen in 16 (26.2%) of 61 patients with chronic liver disease.

Pericaval fat collection near the intrahepatic inferior vena cava is related to anatomic variation of the subdiaphragmatic inferior vena cava, and chronic liver disease. Han et al. reported that the rightward angulation and narrowing of the intrahepatic inferior vena cava caused the pericaval fat collections to appear within the lumen of the inferior vena cava on axial CT images (Figures 90.1 and 90.2).