Confluent Hepatic Fibrosis

Confluent hepatic fibrosis is a mass-like fibrosis seen in approximately 15% of patients with advanced cirrhosis who are candidates for liver transplantation. The imaging findings of confluent fibrosis result in it being characterized due to its specific location in the liver, which is frequently the medial segment of the left and/or right lobe. Calcifications or dilatation of the biliary ducts are very rare.

Imaging techniques such as US are not specific for the diagnosis of confluent hepatic fibrosis; confluent fibrosis typically appears as an ill-defined hyperechoic, heterogeneous area, often with a pseudonodular aspect.

On unenhanced CT, confluent fibrosis often appears as a wedge-shaped focal area of low-density. After contrast material administration the lesion again demonstrates a low level of vascularity but may appear slightly hyperdense in the equilibrium or later phases due to the pooling effect of fibrotic tissue. Typical features such as retraction of the overlying liver capsule are evident on CT (Fig. 19).

Morphologic information on confluent fibrosis is available also after MR imaging, although the MR signal characteristics are not unique and do not permit accurate differentiation of this lesion from hepatic neoplasms. Whereas fibrotic tissue is typically hypointense with either a homogeneous or heterogeneous appearance on unenhanced T1-

and T2-weighted images, confluent hepatic fibrosis appears as a region of lower signal intensity compared to that of the adjacent liver parenchyma on T1-weighted images, and as a region of higher signal intensity on T2-weighted and STIR images. The hyperintense appearance of confluent hepatic fibrosis on T2-weighted images reflects edema within the fibrotic area [40,41].

The appearance of confluent fibrosis on dynamic phase images after the bolus injection of a gadolinium contrast agent is similar to that observed on CT, with hyperintensity typically seen during the equilibrium phase. During the hepato-biliary phase after the administration of a he-patospecific contrast agent, confluent fibrosis typically has a heterogeneously hypointense appearance due to the reduced number of hepatocytes (Fig. 20).

Confluent fibrosis on SPIO-enhanced T2-weighted images characteristically presents as a wedge-shaped area of high signal intensity with internal areas of low signal intensity. While the area of high signal intensity corresponds to the distribution of fibrosis, the low signal intensity regions reflect residual functioning liver parenchyma that is able to take up SPIO particles [33].

The differential diagnosis of confluent fibrosis in cirrhotic patients includes non-neoplastic processes such as segmental fatty liver or hepatic infarction and neoplastic processes such as infil-trative sclerosing HCC. Although irregular fatty infiltration may appear with variable shape and dis-

A d

Fig. 19a-d. Confluent hepatic fibrosis. The pre-contrast CT scan (a) reveals a hypodense area (arrows) located in segment VIII of the liver, associated with capsular retraction. After contrast medium administration, this area shows minor enhancement in the arterial phase (b), while the density increases progressively in the portal venous (c) and equilibrium (d) phases

Fig. 19a-d. Confluent hepatic fibrosis. The pre-contrast CT scan (a) reveals a hypodense area (arrows) located in segment VIII of the liver, associated with capsular retraction. After contrast medium administration, this area shows minor enhancement in the arterial phase (b), while the density increases progressively in the portal venous (c) and equilibrium (d) phases

Fig. 20a-f. Confluent hepatic fibrosis. Same case shown in Fig.19. On the pre-contrast T2-weighted image (a) and on the GRE T1-weight-ed image (b) an area (arrows) located in segment VIII of the liver appears homogeneously, slightly hyperintense and heterogeneously, slightly hypointense, respectively. The enhancement behavior during the dynamic series after administration of Gd-BOPTA is similar to that seen on CT imaging: the area does not show significant enhancement on arterial phase images (c) but shows a progressive increase in signal intensity during the portal venous (d) and equilibrium (e) phases (arrows). On the hepatobiliary phase image (f) after injection of Gd-BOPTA this area appears slightly hypointense compared with the normal liver

Fig. 20a-f. Confluent hepatic fibrosis. Same case shown in Fig.19. On the pre-contrast T2-weighted image (a) and on the GRE T1-weight-ed image (b) an area (arrows) located in segment VIII of the liver appears homogeneously, slightly hyperintense and heterogeneously, slightly hypointense, respectively. The enhancement behavior during the dynamic series after administration of Gd-BOPTA is similar to that seen on CT imaging: the area does not show significant enhancement on arterial phase images (c) but shows a progressive increase in signal intensity during the portal venous (d) and equilibrium (e) phases (arrows). On the hepatobiliary phase image (f) after injection of Gd-BOPTA this area appears slightly hypointense compared with the normal liver tribution, the absence of capsular retraction or segmental shrinkage is often sufficient to distinguish this lesion from confluent fibrosis.Similarly, hepatic infarction can appear as a well-demarcated wedge-shaped area, but these areas typically show little or no enhancement. Moreover, hepatic infarction is rare in cirrhotic patients, occurring more frequently in patients with hematologic disorders after vascular surgery or transplantation. In the case of infiltrative sclerosing HCC, this lesion can be seen as a nearly wedge-shaped or peripheral band-like lesion, although it is usually hypervas-cular during the arterial phase of the dynamic study, showing wash-out in the portal venous phase. Moreover, HCC is frequently associated with a pseudocapsule and often contains areas of necrosis, hemorrhage or fatty metamorphosis within the lesion [40,41].

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