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Hepatic arterioportal shunts: dynamic CT and MR features.

Choi BI, Lee KH, Han JK, Lee JM - Korean J Radiol (2002 Jan-Mar)

Bottom Line: With the increased temporal resolution available in dynamic computed tomography (CT) and magnetic resonance imaging (MRI), hepatic arterioportal shunts are now more frequently encountered than in the past.The condition occurs in various hepatic diseases in which portal or hepatic venous flow is compromised.Familiarity with the pathophysiology of arterioportal shunt also allows investigation of the hepatic hemodynamic changes occurring in various hepatic diseases.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, College of Medicine, Seoul National University Hospital, 28 Yongon-dong, Chongno-gu, Seoul 110-744, Korea. choibi@radcom.snu.ac.kr

ABSTRACT
With the increased temporal resolution available in dynamic computed tomography (CT) and magnetic resonance imaging (MRI), hepatic arterioportal shunts are now more frequently encountered than in the past. The condition occurs in various hepatic diseases in which portal or hepatic venous flow is compromised. The underlying mechanism and the degree of shunt affect its appearance at dynamic imaging. The dynamic CT and MRI findings have been summarized as early enhancement of peripheral portal veins, and wedge-shaped transient parenchymal enhancement during the hepatic arterial phase. Recognition of arterioportal shunt can suggest the presence of a previously unsuspected disorder and avoids false-positive diagnosis or overestimation of a hepatic disease. Familiarity with the pathophysiology of arterioportal shunt also allows investigation of the hepatic hemodynamic changes occurring in various hepatic diseases.

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Related in: MedlinePlus

Attenuation differences secondary to hepatic vein obstruction in a transplanted liver.A. CT scan obtained during portal venous phase shows hypoattenuation of the anterior segment of the transplanted right lobe despite normal enhancement of the portal veins (arrowheads) inside the corresponding area.B. CT scan obtained during the equilibrium phase reveals thrombosed hepatic vein (arrow) which was ligated during surgery. The anterior segment of the transplanted right lobe appears hyperattenuated, producing a negative image of (A). Note that the straight border (small arrows in (A) and (B)) of transient hepatic attenuation difference intersects the portal veins (open arrows in (A) and (B)).
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Figure 2: Attenuation differences secondary to hepatic vein obstruction in a transplanted liver.A. CT scan obtained during portal venous phase shows hypoattenuation of the anterior segment of the transplanted right lobe despite normal enhancement of the portal veins (arrowheads) inside the corresponding area.B. CT scan obtained during the equilibrium phase reveals thrombosed hepatic vein (arrow) which was ligated during surgery. The anterior segment of the transplanted right lobe appears hyperattenuated, producing a negative image of (A). Note that the straight border (small arrows in (A) and (B)) of transient hepatic attenuation difference intersects the portal veins (open arrows in (A) and (B)).

Mentions: Where there is diminished hepatic venous flow, dynamic CT or MRI findings may differ according to the site and chronicity of the occlusion as well as the development of veno-venous collaterals (1, 19). Transient hepatic hyperenhancement may be seen at HAP imaging, and this area has been reported to correspond to a defect seen at CT during arterial portography and/or hyperattenuation seen at CT during hepatic arteriography (12), as in cases of portal venous flow stoppage. The differences are that (a) the straight border of the involved parenchyma intersects with the corresponding branch of the hepatic vein in portal venous occlusion and vice versa in hepatic venous occlusion (16), and (b) the vertex of the wedge-shaped hyperattenuating area points to the hepatic hilum in portal venous occlusion, but to the inferior vena cava in hepatic venous occlusion (1, 16) (Fig. 2). A recent experimental study (19) revealed that acute occlusion of the hepatic vein could induce hypoattenuation in the affected area during PVP imaging, probably because APS occurred at the presinusoidal level (through the transplexal route) and the reversed opacified portal flow escaped from the congested segment. This flow then drained into the segment adjacent to the patent hepatic vein, resulting in transient hyperenhancement. Interestingly, a congested segment was often hyperattenuated at subsequent delayed-phase imaging, a finding which was attributed to delayed washout of the contrast agent (Fig. 2).


Hepatic arterioportal shunts: dynamic CT and MR features.

Choi BI, Lee KH, Han JK, Lee JM - Korean J Radiol (2002 Jan-Mar)

Attenuation differences secondary to hepatic vein obstruction in a transplanted liver.A. CT scan obtained during portal venous phase shows hypoattenuation of the anterior segment of the transplanted right lobe despite normal enhancement of the portal veins (arrowheads) inside the corresponding area.B. CT scan obtained during the equilibrium phase reveals thrombosed hepatic vein (arrow) which was ligated during surgery. The anterior segment of the transplanted right lobe appears hyperattenuated, producing a negative image of (A). Note that the straight border (small arrows in (A) and (B)) of transient hepatic attenuation difference intersects the portal veins (open arrows in (A) and (B)).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2713981&req=5

Figure 2: Attenuation differences secondary to hepatic vein obstruction in a transplanted liver.A. CT scan obtained during portal venous phase shows hypoattenuation of the anterior segment of the transplanted right lobe despite normal enhancement of the portal veins (arrowheads) inside the corresponding area.B. CT scan obtained during the equilibrium phase reveals thrombosed hepatic vein (arrow) which was ligated during surgery. The anterior segment of the transplanted right lobe appears hyperattenuated, producing a negative image of (A). Note that the straight border (small arrows in (A) and (B)) of transient hepatic attenuation difference intersects the portal veins (open arrows in (A) and (B)).
Mentions: Where there is diminished hepatic venous flow, dynamic CT or MRI findings may differ according to the site and chronicity of the occlusion as well as the development of veno-venous collaterals (1, 19). Transient hepatic hyperenhancement may be seen at HAP imaging, and this area has been reported to correspond to a defect seen at CT during arterial portography and/or hyperattenuation seen at CT during hepatic arteriography (12), as in cases of portal venous flow stoppage. The differences are that (a) the straight border of the involved parenchyma intersects with the corresponding branch of the hepatic vein in portal venous occlusion and vice versa in hepatic venous occlusion (16), and (b) the vertex of the wedge-shaped hyperattenuating area points to the hepatic hilum in portal venous occlusion, but to the inferior vena cava in hepatic venous occlusion (1, 16) (Fig. 2). A recent experimental study (19) revealed that acute occlusion of the hepatic vein could induce hypoattenuation in the affected area during PVP imaging, probably because APS occurred at the presinusoidal level (through the transplexal route) and the reversed opacified portal flow escaped from the congested segment. This flow then drained into the segment adjacent to the patent hepatic vein, resulting in transient hyperenhancement. Interestingly, a congested segment was often hyperattenuated at subsequent delayed-phase imaging, a finding which was attributed to delayed washout of the contrast agent (Fig. 2).

Bottom Line: With the increased temporal resolution available in dynamic computed tomography (CT) and magnetic resonance imaging (MRI), hepatic arterioportal shunts are now more frequently encountered than in the past.The condition occurs in various hepatic diseases in which portal or hepatic venous flow is compromised.Familiarity with the pathophysiology of arterioportal shunt also allows investigation of the hepatic hemodynamic changes occurring in various hepatic diseases.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, College of Medicine, Seoul National University Hospital, 28 Yongon-dong, Chongno-gu, Seoul 110-744, Korea. choibi@radcom.snu.ac.kr

ABSTRACT
With the increased temporal resolution available in dynamic computed tomography (CT) and magnetic resonance imaging (MRI), hepatic arterioportal shunts are now more frequently encountered than in the past. The condition occurs in various hepatic diseases in which portal or hepatic venous flow is compromised. The underlying mechanism and the degree of shunt affect its appearance at dynamic imaging. The dynamic CT and MRI findings have been summarized as early enhancement of peripheral portal veins, and wedge-shaped transient parenchymal enhancement during the hepatic arterial phase. Recognition of arterioportal shunt can suggest the presence of a previously unsuspected disorder and avoids false-positive diagnosis or overestimation of a hepatic disease. Familiarity with the pathophysiology of arterioportal shunt also allows investigation of the hepatic hemodynamic changes occurring in various hepatic diseases.

Show MeSH
Related in: MedlinePlus