Hepatic Sinusoidal Dilatation: A Review of Causes With Imaging-Pathologic Correlation☆
Introduction
The hepatic sinusoids are vascular conduits connecting the portal triad with the central vein lined by fenestrated endothelial cells and Kupffer cells (Fig. 1). The sinusoids have a key role in the regulation of the hepatic microcirculation: oxygen, nutrients, and toxins are transported between the vascular space and the hepatocytes through sinusoids.1, 2
Multiple conditions can lead to sinusoidal dilatation and sinusoidal congestion with erythrocytes.1, 2, 3, 4 Stasis of blood within hepatic sinusoids and the altered hemodynamics that occur with decreased venous outflow-compensatory increased arterial inflow manifest as heterogeneous enhancement of the hepatic parenchyma on contrast-enhanced computed tomography (CT) and magnetic resonance (MR) imaging (MRI)—an appearance commonly referred to as a “mosaic” enhancement pattern.5, 6, 7, 8 The affected parenchyma shows reticular areas of enhancement interleaved with ill-defined areas of hypoenhancement. The pattern is generally more conspicuous on images acquired during the late arterial and portal venous phase.5, 9
In this article, we review the different etiologies of hepatic sinusoidal dilatation and their imaging manifestations on contrast-enhanced CT and MR.
Section snippets
CT and MRI Protocol
The routine CT protocol for the evaluation of liver disease consists of multiple postcontrast phases. Images are commonly acquired during the late hepatic arterial (“portal venous inflow”) and portal venous phases, 30-35 seconds and 70-80 seconds following injection of iodinated intravenous contrast, respectively.10 Additional precontrast and delayed phases (ie, >120 seconds postcontrast administration) may also be acquired, but protocols vary according to indication and institution. The MRI
Hepatic Sinusoidal Dilatation
Sinusoidal dilatation can be classified based upon the most prevalent distribution in the hepatic lobule as centrilobular, periportal, or irregular.12 Most commonly, the process affects the centrilobular zone (zone 3) (Fig. 2). Severe sinusoidal dilatation may have a similar appearance to hepatic peliosis, and the differentiation between the two may be difficult. The latter, however, is characterized by randomly distributed blood-filled spaces (“lakes”) associated with incomplete lining of
Conclusions
A gamut of hepatic and systemic etiologies results in hepatic sinusoidal dilatation. This condition can be seen both in association with, or in the absence of, hepatic outflow venous obstruction. The resulting hepatic congestion and altered hemodynamics usually manifests as a “mosaic” pattern of enhancement at contrast-enhanced CT and MRI. Recognizing additional imaging features helps in the differential diagnosis of these conditions.
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Presented at RSNA 2015—Education Exhibit GI191-ED-X: Stuck in the Liver: Causes of Hepatic Sinusoidal Dilatation Resulting in “Mosaic” Enhancement Pattern.