Pseudolipoma of the IVC

A 75-year-old man presented to the ER with left-sided lower abdominal pain. He reported no other complaints. He gave a history of diverticulitis and chronic obstructive pulmonary disease. Abdomenal examinations revealed generalised rigidity and tenderness in left fossa. Rectal exploration: normal faeces. Laboratory results showed increased CRP and leukocytosis.

Contrast-enhanced computed tomography (CT) of abdomen was performed, which revealed signs of acute diverticulis. CT revealed also hepatic steatosis and on axial images (Fig. 1) showed a rounded, well-defined, fat-containing lesion (-96 H), medial to the inferior vena cava (IVC), which initially appeared to lie intraluminally in the intrahepatic IVC because of a thin medial line resembling medial wall of the IVC. However, coronal reformation (Fig. 2) revealed its true location to be juxtacaval, medial to the IVC, contiguous to the subdiaphragmatic fat tissue, and the thin medial line contiguous to the diaphragm.

Pseudolipoma of the IVC refers to localised collection of adipose tissue adjacent to the intrahepatic portion of the IVC. It is regarded as an uncommon incidental normal variant with a prevalence of 0.5-0.55% in adults undergoing abdominal CT. It occurs more commonly in patients with liver disease and might be related to obesity or anatomical variation. [1, 2]
It usually appears as an oval or round collection in transverse sections, with attenuation values in the range as those for fat tissue.
It is typically located at or superior to the confluence of the hepatic veins and the IVC, usually observed medial or posterior to the IVC, and contiguous to the subdiaphragmatic fat tissue. [1, 3]
It is suggested that atrophy of the right hepatic lobe creates a pericaval space between the diaphragm and the IVC, and this space becomes filled by juxtacaval fat. [1, 3]
On axial images it may simulate serious intraluminal lesions of the IVC such as thrombus, tumours or intraluminal lipoma.
Reformatted images and ultrasound are used in identifying its juxtacaval location. Therefor awareness of the radiologists of this entity is important to avoid misdiagnosis and subsequent unnecessary intervention. [1, 2, 3, 4]

In this case, the juxtacaval fat appeared to be intraluminal on axial images, however, coronal reformatted images revealed its true position to be juxtacaval and a review of previous CT abdomen images of the patient revealed no changes in its appearance and size.