British Journal of Radiology 75 (2002),69-71 © 2002 The British Institute of Radiology
Ultrasound and CT findings in lipoma of the inferior vena cava
R Grassi, MD,
R Di Mizio, MD,
A Barberi, MD,
S Severini, MD,
A Del Vecchio, MD and
S Cappabianca, MD
Seconda Universitá degli Studi di Napoli, Facoltá di Medicina e Chirurgia, Dipartimento Universitario "F. Magrassi, G. Lanzara", Ex Istituto di Scienze Radiologiche, Italy
Correspondence: Dott. Salvatore Cappabianca, Viale Farnese 36, 80131–Napoli, Italy
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Abstract
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Several cases of a fat mass-like lesion adjacent to and/or projecting into the inferior vena cava have been presented as a normal variant of perioesophageal fat distribution or as intravascular lipoma. We report a case of a lipoma of the inferior vena cava, studied with coronal reformatted CT images, ultrasound and colour Doppler imaging, in a 78-year-old female patient.
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Introduction
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Several cases of a fat mass-like lesion adjacent to and/or projecting into the inferior vena cava (IVC), superior vena cava, brachiocephalic vein and femoral vein, studied with CT, MRI, venography, ultrasound and duplex Doppler have been described previously [1–10]. Between 1992 and 1999, 32 cases of these lesions related to the subdiaphragmatic portion of the intrahepatic portion of the IVC have been reported, mostly presented as a normal variant of perioesophageal fat distribution without clinical significance [1, 2, 6, 8], while others have termed these benign fat structures as intravascular lipoma [3, 4]. Recently, a case of an intraluminal fat mass of the femoral vein, studied with CT, MRI, Doppler ultrasound and venography, has been reported, the surgical resection and pathology examination of which showed a benign lipoma arising from the venous wall [9].
We report a case of a lipoma of the IVC, studied with coronal reformatted CT images, ultrasound and colour Doppler imaging (CDI).
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Case report
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The patient, who was a slightly obese (body mass index=32) female aged 78 years, underwent surgical treatment for carcinoma of the urinary bladder. She underwent a follow-up abdominal ultrasound examination after six cycles of chemotherapy. Biochemical investigations were normal. The patient complained only of non-specific intermittent abdominal pain. Ultrasound demonstrated a hyperechoic mass-like lesion anteromedial to the IVC, and the caval lumen appeared reduced in diameter (Figure 1
). CDI of the region was performed to evaluate the haemodynamic significance of IVC involvement. This demonstrated an intraluminal portion to the mass, while the caval flow showed a mosaic pattern but no signs of absent or turbulent flow (Figure 2). The patient subsequently underwent helical CT (HeliCAT II; Marconi Co, Cleveland, OH) using 5 mm slice collimation and reconstruction, pitch 1.5, before and during intravenous administration of 140 ml of iodinated contrast medium at a flow rate of 3 ml s-1 and a scan delay of 12 s to obtain both arterial and venous phases of contrast medium transit. Helical CT images showed a low attenuation unenhanced mass-like structure anteromedial to the intrahepatic segment of the IVC, contiguous with the fat around the subdiaphragmatic oesophagus but also with an endoluminal rounded portion at the level of cranial scans, mimicking an intracaval fat thrombus (Figure 3). The coronal reformatted images provided a better depiction of the fatty mass; the lesion measured 2.33 cm x 6.05 cm and appeared to lie outside the IVC in the space between the IVC and the diaphragm (Figure 4).
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Figure 1. Ultrasound examination showing an inhomogeneous, slightly hyperechoic mass lesion (arrows) anteromedial to the inferior vena cava. The caval lumen appears reduced in diameter.
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Figure 2. Colour Doppler imaging demonstrates an intraluminal portion of the mass. Caval flow showed a mosaic pattern, but no signs of occluded or turbulent flow are identified.
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Figure 3. Contrast enhanced helical CT showing a low attenuation non-enhancing mass-like structure (arrow), completely within the lumen and having a rounded portion that mimics an intracaval fat thrombus.
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Figure 4. Coronal reformatted image provides a better depiction of the course of the fatty lesion (arrows), which appears to lie outside the inferior vena cava (IVC) in the space between the IVC and the diaphragm.
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The patient refused MRI examination, surgery or other further investigations. CT 18 months prior to surgery had shown that the lesion had the same morphology, density and size.
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Discussion
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In 1992, Miyake et al [1] described the first 11 cases of focal collections of fat appearing as a mass adjacent to the intrahepatic portion of the IVC at or above the level of confluence of the hepatic veins and IVC. These lesions were oval or round in shape and ranged in size from 10 mm to 22 mm. Three of the lesions were studied with MRI, and appeared on T1 weighted images as high intensity signal masses clearly contiguous with the high intensity fat around the oesophagus. Coeliac arteriography performed in three cases showed no abnormality in the area of the fat collection [1]. A further 21 similar cases, studied with different imaging techniques, were reported between 1992 and 1999. These localized caval fat collections were first identified in a series of 2227 consecutive Japanese patients [1] and in another series of 1470 consecutive western patients [3], with a frequency of, respectively, 0.5% and 0.55%. We ourselves have evaluated the upper abdomen and thorax CT studies of 5259 subjects, but observed only this reported case.
Only two cases of IVC lipoma studied with ultrasound had been reported, one appearing slightly hypoechoic relative to liver [2], while the other was hyperechoic and associated with a doubling of the flow velocity in the IVC on duplex Doppler ultrasound, indicating a significant obstruction to venous return [3].
Several factors may account for the small number of cases reported on ultrasound: the usual small size of the IVC fat lesions, their subdiaphragmatic location next to the heart and the presence of surrounding fat tissue, which is relatively isoechoic to the intravascular fatty mass.
Some authors [6] have considered that these fat mass-like lesions show only an apparent intracaval portion on axial ultrasound and CT images because of a right angulation to the vertical plane and the narrowing of IVC at the subdiaphragmatic level. The particular anatomical relationship between the IVC, surrounding fat tissue and the diaphragmatic crus explains the fat mass appearing as an intraluminal collection. Nevertheless, others [3] described fatty masses as intraluminal entities on the basis of standard radiological criteria because they presented an acute angle between its edge and the wall of IVC with a ring of contrast enhanced material around the mass and these authors have consequently termed these benign fat structures as lipomas. In the absence of surgical exploration or autopsy, two distinct processes have been hypothesized: the first, a normal anatomical variant of pericaval fat distribution; the second, a lipoma within the vessel that could be found in patients with various pathologies, particularly hepatic diseases such as cirrhosis, hepatocellular carcinoma and hepatoma [3, 6].
In reality, there is no direct correlation between the lipoma of the IVC and liver pathology, because these lesions were also identified in patients with a number of unrelated pathologies [1, 2, 6, 7]. Only one subject presented with obesity and mediastinal lipomatosis [8] such as our patient. Consequently, these lesions do not represent a manifestation of increased fat body mass.
Only one case of fatty collection in the IVC wassurgically confirmed after blunt abdominal trauma had caused a laceration of the IVC, although there was no pathological examination in this case [7].
Two cases of fatty lesions related to the superior vena cava, appearing on CT and MRI to be clearly intraluminal because of the small amount of fat tissue surrounding the venous wall, have been described in the literature [5, 10].
Recently, a case of femoral vein lipoma was reported and confirmed on resection and pathological examination as arising from the venous wall and associated with local attenuation of the vein wall between the endothelium and adventitia. Obstruction to flow was present despite the benign nature of the lesion [9].
The nature, origin and intraluminal or extraluminal location of the fatty lesions related to the subdiaphragmatic portion of the IVC is still a vexed question because of the absence of any pathological examination. Although an association between IVC lipoma and alteration in flow has been reported [3], the benign nature of these lesions is confirmed by the absence of signs and symptoms of significant obstruction to the IVC. In all reported cases without liver disease, there has been no reported occurrence of Budd–Chiari syndrome [11].
Received for publication June 11, 2001.
Revision received September 11, 2001.
Accepted for publication September 18, 2001.
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References
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Abstract
Introduction
