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Imaging Features of Perivascular Fatty Infiltration of the Liver: Initial Observations¹

¹ From the Department of Radiology, Division of Body Imaging, UCSD Medical Center San Diego, 200 W Arbor Dr, San Diego, CA 92103-8756. Received September 12, 2004; revision requested November 18; revision received January 24, 2005; accepted February 24. Address correspondence to C.B.S. (e-mail: csirlin{at}ucsd.edu)

View larger version (71K): [in a new window]   Figure 1. Transverse portal venous phase CT images in 45-year-old man with biopsy-proved alcoholic cirrhosis (patient 3) show well-defined hypoattenuating halos of fatty infiltration (white arrows) around hepatic veins in both lobes of liver. The morphologic structure of halos is tramlike on A, the higher-level scan, in which the hepatic veins are parallel to the imaging plane. On B, the more caudal scan, in which hepatic veins are perpendicular to the imaging plane, the halos have a round or ringlike appearance. Small hepatic veins inside some halos (black arrows in B) are poorly depicted because of location at a lower level in the cross section. Attenuation of fatty tissue (37 HU) on these images is distinctly lower than that of spared liver parenchyma (80 HU) and meets imaging criteria for fatty infiltration of the liver.

View larger version (133K): [in a new window]   Figure 2. Coronal (A, B) and transverse (C, D) MR images in 58-year-old woman with biopsy-proved alcoholic cirrhosis (patient 2). In-phase images (A, C) were obtained with 204/4.76 (repetition time msec/echo time msec) and a flip angle of 30°. Opposed-phase images (B, D) were obtained with 204/2.65 and a flip angle of 30°. Fatty tissue (arrows) surrounding the hepatic veins is subtly hyperintense on in-phase images and shows unequivocal signal loss on opposed-phase images, features that confirm perivascular fatty infiltration of the liver. The apparent affinity of infiltration for the upper liver segments as opposed to the lower ones on these images is related to section selection; perivenous fatty infiltration of the liver involved all liver segments. Halos that surround hepatic veins in the imaging plane (coronal images) are tramlike, and those that surround veins perpendicular to the imaging plane (transverse images) are ringlike or round. Note also the evidence of perihepatic ascites on all images.

View larger version (60K): [in a new window]   Figure 3. Oblique coronal (A) and oblique transverse (B) thick-slab reformations from portal venous phase CT scanning in 45-year-old man with biopsy-proved alcoholic cirrhosis (same patient as in Fig 1) help to confirm a perivenous pattern of perivascular fatty infiltration of the liver.

View larger version (125K): [in a new window]   Figure 4. Transverse CT images at level of liver in 45-year-old woman with abdominal pain and history of daily alcohol consumption (patient 1). Images obtained before intravenous administration of contrast material (A) and during the hepatic arterial phase (B), portal venous phase (C), and equilibrium phase (D) show well-defined hypoattenuating halos that tightly cloak the hepatic veins in both lobes on images of all phases. Mean attenuation of hypoattenuating zones on unenhanced images was 28 HU. Infiltration was subjectively considered most conspicuous on portal venous phase and equilibrium phase images.

View larger version (151K): [in a new window]   Figure 5. Coronal (A, B) and transverse (C, D) MR images in 45-year-old woman with abdominal pain and history of daily alcohol consumption (same patient as in Fig 4) show halos with hyperintense signal on in-phase images (A, C; obtained with 204/4.76 and flip angle of 30°) and signal loss on opposed-phase images (B, D; obtained with 204/2.65 and flip angle of 30°), features that confirm the presence of perivascular fatty infiltration. The pattern of infiltration is virtually identical to that on the CT images in Figure 4.

View larger version (72K): [in a new window]   Figure 6. Transverse (A) and sagittal (B) transabdominal gray-scale US images of liver in 58-year-old woman with biopsy-proved alcoholic cirrhosis (same patient as in Fig 2). US images, obtained with a sector transducer, show irregular bands and vaguely nodular areas of hyperechogenicity (arrows). The perivenous distribution is not appreciable, in part because the intrahepatic vessels are poorly depicted. Exclusion of underlying neoplasia is not possible.

View larger version (163K): [in a new window]   Figure 7. Transverse CT images at level of liver in 35-year-old man with history of regular alcohol consumption and clinical diagnosis of human immunodeficiency virus (patient 5). Images obtained before intravenous administration of contrast material (A) and during the hepatic arterial phase (B), portal venous phase (C), and equilibrium phase (D) show hypoattenuating (mean attenuation on unenhanced images, –17 HU) halos around portal tracts (arrows in C), sparing of liver periphery in the right lobe (arrows in D), and ill-defined confluent zones of perivascular infiltration in the left lobe that mimic a diffuse pattern of fatty infiltration of the liver. Careful review of all images indicated a predisposition of periportal zones to fatty infiltration. Infiltration was subjectively considered most conspicuous on hepatic arterial phase and portal venous phase images.

View larger version (65K): [in a new window]   Figure 8. Transverse portal venous phase CT images in 78-year-old woman with no known risk factors for fatty infiltration of the liver (patient 6). Image obtained at initial CT examination (A) shows two portal tracts (arrows) surrounded by well-defined hypoattenuating tissue (30 HU). The abnormality persisted but was less conspicuous on images from follow-up examinations at 52 weeks (B) and 54 weeks (C), as confirmed by quantitative measurements. CNR for spared liver to fatty infiltration was 7, 5, and 1 at the first, second, and third (last) CT examinations, respectively. There were slight differences in depth of inspiration between the serial examinations. The hypoattenuation of central liver segments relative to peripheral liver segments in B and C may represent mild fatty infiltration in these areas but did not fulfill the imaging criteria for diagnosis of fatty infiltration of the liver.