A paracaval lipoma (also known as juxtacaval fat collection or pseudolipoma of the inferior vena cava) refers to an apparent protrusion of paracaval fat into the inferior vena cava (IVC) and is commonly visible on CT; some believe it to be a normal anatomic variant 1.
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Epidemiology
Paracaval lipoma may be seen in up to 0.5% of CT examinations 2.
Associations
It may be seen in patients with cirrhosis 3.
Pathology
The paracaval lipoma appearance is thought to be due to volume averaging through inwards and upwards indrawing of the posteromedial wall of the inferior vena cava as a result of negative pressure created within the thorax on inspiration 4.
Radiographic findings
CT
Paracaval lipoma occurs at the medial aspect of the intrahepatic portion of the inferior vena cava (IVC) above the caudate lobe and represents pericaval fat appearing to invaginate into the inferior vena cava. Attenuation values is measure usually falls the in the compatible with macroscopic fat.
Ultrasound
In some situations may be seen as a echogenic, homogeneous nodule in the hepatic segment of the IVC at its junction with the right atrium 5.
Differential diagnosis
On imaging consider
bland thrombus in the inferior vena cava
tumors of the inferior vena cava, e.g. leiomyosarcoma 6