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Spontaneous Intrahepatic Vascular Shunts

¹ Department of Radiology, Brooke Army Medical Center, 3851 Roger Brooke Dr., Ft. Sam Houston, San Antonio, TX 78234.
² Department of Radiology, Stanford University Medical Center, 300 Pasteur Dr., Stanford, CA 94305.
³ Department of Radiology, Winthrop University Hospital, 259 First St., Mineola, NY 11501.

Received March 1, 1999; accepted after revision June 9, 1999.

 
Address correspondence to M. J. Lane.

Introduction

Top Introduction Portosystemic Venous Shunt Arterioportal Shunts Arteriosystemic Shunts References

 
Multiphase helical CT and multiphase dynamic MR imaging represent advances in cross-sectional imaging that allow evaluation of the liver during arterial and portal venous phases of contrast enhancement. A recent article describes perfusion disorders of the liver as manifestations of increased attenuation [1]. However, abnormal communication between the hepatic arteries, portal veins, or hepatic veins have been described in relatively few reports. Although communication within the liver between the hepatic artery and portal vein has been reported, including transsinusoidal, transvasal, and transplexal routes, these vascular communications are typically small and below the threshold of visualization with cross-sectional imaging [2].

The frequency in which large intrahepatic vascular shunts are visualized on cross-sectional imaging is unknown. Large shunts may appear as hypervascular lesions and may occasionally simulate primary neoplasms of the liver. Recognition of large shunts can provide insight into the patient's pathophysiology, especially in cirrhosis and portal hypertension. This pictorial essay will review conditions associated with known and unknown abnormalities of large intrahepatic shunts, their appearances on multiphase contrast-enhanced CT and MR imaging, and their sonographic and angiographic correlation.

Three types of intrahepatic shunts between the major vessels of the liver are possible: portosystemic venous (portal vein to hepatic vein or vena cava), arterioportal (hepatic artery to portal vein), and arteriosystemic (hepatic artery to hepatic vein). Visualization of these shunts on cross-sectional imaging is unusual. Most shunts, particularly portosystemic shunts, are identified in the setting of cirrhosis. Intrahepatic portosystemic shunts may also be congenital or posttraumatic in origin. Arterioportal shunts are typically associated with hepatocellular carcinoma (HCC), vascular malformations involving the liver, or benign hepatic neoplasms; they may also be iatrogenic after biopsy. Recently, idiopathic nontumoral arterioportal shunts have been researched [3]. Arteriosystemic intrahepatic shunts are rare and are typically associated with hepatic neoplasms.

Portosystemic Venous Shunt

Top Introduction Portosystemic Venous Shunt Arterioportal Shunts Arteriosystemic Shunts References

 
Intrahepatic portosystemic (portal to hepatic) venous shunts are uncommon. Postulated congenital origins of portosystemic shunts include the persistence of an omphalomesenteric venous system with the right horn of the sinus venosus or rupture of a portal vein aneurysm into a hepatic vein [4]. Acquired conditions such as trauma and portal hypertension are also theorized [5]. Portosystemic shunts are typically identified incidentally as part of the workup for cirrhosis or, less commonly, after a patient's condition is diagnosed as hepatic encephalopathy [4] (Fig. 1).

View larger version (123K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1. —65-year-old man with portosystemic shunt undergoing evaluation for cirrhosis. Arterial phase CT scan shows direct communication of left portal vein (curved arrow) and middle hepatic vein (straight arrow).

Patients with severe portal hypertension can develop extensive portosystemic collaterals draining directly into the inferior vena cava by way of a subcapsular route [5] (Fig. 2A, Fig. 2B). Sonography can identify the communication between the portal vein and the hepatic or systemic veins (Fig. 3A, Fig. 3B, Fig. 3C, Fig. 3D).

View larger version (160K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2. —58-year-old woman with hepatic encephalopathy and portosystemic shunt. A, Contrast-enhanced CT scan shows dilated right portal vein (curved arrow) and large subcapsular systemic vein (straight arrow) emptying into inferior vena cava. Note splenic infarcts, splenic artery aneurysm (A), and bilateral pleural effusions.

View larger version (153K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2. —58-year-old woman with hepatic encephalopathy and portosystemic shunt. B, Contrast-enhanced CT scan caudal to A shows dilated right portal vein communicating with large subcapsular systemic vein (curved arrow).

View larger version (117K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3. —47-year-old man with portosystemic shunt undergoing evaluation for cirrhosis. A, Contrast-enhanced portal venous-phase CT scan shows dilated right portal vein (arrow).

View larger version (89K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3. —47-year-old man with portosystemic shunt undergoing evaluation for cirrhosis. B, Contrast-enhanced portal venous-phase CT scan shows aneurysmal site of communication (curved arrow) between right portal vein and right hepatic vein.

View larger version (136K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3. —47-year-old man with portosystemic shunt undergoing evaluation for cirrhosis. C, Contrast-enhanced portal venous-phase CT scan shows dilated right hepatic vein (arrow) and normal-appearing middle and left hepatic veins (arrowheads).

View larger version (162K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3. —47-year-old man with portosystemic shunt undergoing evaluation for cirrhosis. D, Power Doppler sonogram shows direct communication between portal (straight arrow) and hepatic (curved arrow) veins.

Arterioportal Shunts

Top Introduction Portosystemic Venous Shunt Arterioportal Shunts Arteriosystemic Shunts References

 
Arterioportal shunts occur in liver disorders such as cirrhosis, trauma, congenital vascular malformations, and hepatic neoplasms. Arterioportal shunting associated with cirrhosis or HCC is also well documented [6]. The degree of shunting is greater with neoplasms than with cirrhosis and even greater with large tumors. Research shows that the prevalence of arterioportal shunting in HCC is as high as 63% of patients [6]. The hepatic artery supplies HCC almost exclusively, providing the intense early enhancement seen in arterial phase imaging. The tendency for these neoplasms to grow in the portal veins causes the venules to act as efferent vessels for the tumor, establishing the arterioportal shunt. The CT or MR imaging findings of arterioportal shunting include early and prolonged enhancement of the portal vein, transient wedge-shaped enhancement peripheral to the tumor (if one is present), and dilated intrahepatic vessels during arterial phase imaging [6].

Intrahepatic nontumorous arterioportal shunts can be idiopathic, resulting from penetrating trauma, or iatrogenic after liver biopsy or percutaneous catheterization of the bile ducts [3]. The abnormally enhancing vein is often enlarged because of the higher systemic pressures presented by the hepatic artery. Enlarged hepatic arteries may also be seen in the vicinity of the shunt. Idiopathic intrahepatic nontumoral arterioportal shunts are typically subcapsular or peripheral as seen angiographically or on arterial phase helical CT (Fig. 4A, Fig. 4B). They appear as focal increased-attenuation wedge-shaped defects with early portal venous filling [3]. Additionally, small idiopathic nontumoral arterioportal shunts have been shown to simulate small hypervascular masses such as HCC, focal nodular hyperplasia, and hemangiomas.

View larger version (132K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4. —55 year-old man with elevated liver function tests and arterioportal shunt. A, Contrast-enhanced arterial phase CT scan shows wedge-shaped subcapsular region of increased attenuation (straight arrow). Note early portal venous filling (curved arrow), representing small idiopathic nontumoral arterioportal shunt confirmed angiographically (not shown).

View larger version (159K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4. —55 year-old man with elevated liver function tests and arterioportal shunt. B, Corresponding portal venous-phase CT scan shows no abnormalities.

Infrequently, intrahepatic arterioportal shunts may cause life-threatening portal hypertension (Fig. 5A, Fig. 5B, Fig. 5C, Fig. 5D). Surgical intervention is necessary only when interventional radiologic procedures such as emoblization have failed. The shunt or fistula between the hepatic artery and the portal vein is rarely visualized on CT.

View larger version (113K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5. —70-year-old man with hematemesis and arterioportal shunt. A, Contrast-enhanced arterial phase CT scan shows cirrhotic-appearing liver. Note dilatation of peripheral hepatic arterial branch (straight arrow) and dilated right portal vein (curved arrow).

View larger version (119K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5. —70-year-old man with hematemesis and arterioportal shunt. B, Gray-scale sonogram shows dilated hepatic artery branches (straight arrows) and right portal vein (curved arrow). Spectral Doppler imaging (not shown) showed arterial waveform in right portal vein, consistent with arterioportal shunting.

View larger version (111K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5. —70-year-old man with hematemesis and arterioportal shunt. C, Selective hepatic arteriogram shows dilated hepatic arteries (curved arrow) feeding vascular malformation.

View larger version (104K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5. —70-year-old man with hematemesis and arterioportal shunt. D, Delayed selective hepatic arteriogram shows portal venous filling (straight arrow) and esophageal varices (curved arrow).

Hereditary hemorrhagic telangiectasia or Osler-Weber-Rendu disease is an autosomal dominant disorder that may involve virtually every organ and is reported to involve the liver in 8-31% of patients [7]. The hepatic manifestations of this disorder include vascular malformations, cirrhosis, and fibrosis [7]. Arterioportal or arteriosystemic venous shunts are also described as manifestations of this congenital disorder. However, identification of a specific abnormal communication in the presence of multiple hepatic vascular malformations can be challenging. The appearance of an early enhancing portal or hepatic vein during the arterial phase of the CT or MR imaging examination is the clue to the diagnosis. Color and Doppler sonography can identify the presence of vascular malformations and the arterioportal or arteriosystemic venous shunts and their hemodynamic significance. Identifying the arterialized waveform in a portal vein may help direct angiography to determine the need for embolization [7] (Fig. 6A, Fig. 6B, Fig. 6C, Fig. 6D).

View larger version (147K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6. —51-year-old woman with Osler-Weber-Rendu disease and arterioportal shunt. A, Contrast-enhanced arterial phase CT scan shows small vascular malformations throughout liver. Note early filling of dilated left portal vein (straight arrow) adjacent to dilated left hepatic artery (curved arrow), suggestive of arterioportal shunt.

View larger version (165K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6. —51-year-old woman with Osler-Weber-Rendu disease and arterioportal shunt. B, Portal venous-phase CT scan shows lesions to be isodense to healthy hepatic parenchyma.

View larger version (117K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6. —51-year-old woman with Osler-Weber-Rendu disease and arterioportal shunt. C, Color Doppler sonogram shows reversal of flow (arrow) in left portal vein.

View larger version (143K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6. —51-year-old woman with Osler-Weber-Rendu disease and arterioportal shunt. D, Spectral Doppler sonogram (with color assignment change compared with C) shows arterialized portal venous waveform, confirming arterioportal shunt.

Arterioportal shunts are rarely reported in association with hepatic hemangiomas [8]. The characteristic appearance of hemangiomas on CT or MR imaging, coupled with the identification of a dilated feeding artery and early portal venous filling, should lead to the correct diagnosis. The degree of shunting determines whether manifestations of portal hypertension are present [9] (Fig. 7A, Fig. 7B, Fig. 7C, Fig. 7D, Fig. 7E, Fig. 7F). When subcapsular, small hemangiomas may simulate a small arterioportal shunt without a coexisting lesion. Peripheral wedge-shaped regions of increased perfusion that become isodense or isointense on delayed images can be seen with small hemangiomas and arterioportal shunts [3, 8].

View larger version (84K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7. —50-year-old man with hematemesis and arterioportal shunt. A, Contrast-enhanced arterial phase CT scan shows nodular enhancement (arrow) in low-attenuation lesion near dome of liver. Lesion filled with contrast material on delayed images (not shown). Ascites is present.

View larger version (92K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7. —50-year-old man with hematemesis and arterioportal shunt. B, Contrast-enhanced arterial phase CT scan caudal to A shows aneurysmal site of communication between dilated hepatic artery (arrow) and early contrast enhancement in main portal vein (arrowhead).

View larger version (144K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7. —50-year-old man with hematemesis and arterioportal shunt. C, Contrast-enhanced arterial phase CT scan near porta hepatis shows cirrhotic-appearing liver, ascites, splenomegaly, dilated tortuous hepatic artery (straight arrow), and early contrast enhancement of main portal vein (curved arrow).

View larger version (122K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7. —50-year-old man with hematemesis and arterioportal shunt. D, Coronal contrast-enhanced three-dimensional spoiled gradient-recalled MR angiogram during arterial phase shows dilated hepatic artery (straight arrow) arising from celiac axis (C). Note early retrograde filling of main portal vein (curved arrow). Nodular enhancement of hemangioma (arrowheads) is seen near liver dome.

View larger version (114K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7. —50-year-old man with hematemesis and arterioportal shunt. E, Selective arteriogram shows dilated hepatic artery filling hemangioma (arrowheads) near liver dome.

View larger version (128K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7. —50-year-old man with hematemesis and arterioportal shunt. F, Delayed arteriogram shows early filling of portal vein (arrow), consistent with arterioportal shunt within hemangioma.

Arteriosystemic Shunts

Top Introduction Portosystemic Venous Shunt Arterioportal Shunts Arteriosystemic Shunts References

 
Arteriosystemic shunts involving the liver are rare and are typically associated with benign and malignant neoplasms. The first description of arteriosystemic venous shunting with a cavernous hemangioma (Fig. 8A, Fig. 8B, Fig. 8C, Fig. 8D, Fig. 8E) was seen in the setting of HCC and arterioportal shunting [8]. Whether the arteriosystemic shunting was related to the arterioportal shunting was unclear. The actual incidence of arteriosystemic shunting in the setting of HCC is unknown, but the incidence of hepatic venous invasion by tumor is thought to be approximately 15% [10]. Therefore, when arteriosystemic shunting to the hepatic veins is observed, invasion of the hepatic veins by HCC should be suspected (Fig. 9A, Fig. 9B).

View larger version (128K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8. —65-year-old woman with hemangioma and arteriosystemic shunt. A, Contrast-enhanced arterial phase CT scan shows wedge-shaped increased attenuation in right lobe of liver with enlarged right hepatic vein (arrow) and early venous filling representing arteriosystemic venous shunting.

View larger version (122K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8. —65-year-old woman with hemangioma and arteriosystemic shunt. B, Caudal arterial phase CT scan shows vascular subcapsular lesion with peripheral nodular enhancement consistent with hemangioma (arrowheads).

View larger version (103K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8. —65-year-old woman with hemangioma and arteriosystemic shunt. C, Axial T2-weighted fat-saturated MR image shows hyperintense lobular lesion in right lobe of liver (arrow).

View larger version (121K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8. —65-year-old woman with hemangioma and arteriosystemic shunt. D, Arterial phase coronal contrast-enhanced three-dimensional spoiled gradient-recalled MR angiogram shows nodular peripheral enhancement of subcapsular hemangioma (arrow). Wedge-shaped area of increased intensity surrounding lesion is also shown (arrowheads).

View larger version (124K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8. —65-year-old woman with hemangioma and arteriosystemic shunt. E, Portal venous coronal contrast-enhanced three-dimensional spoiled gradient-recalled MR angiogram shows filling of subcapsular lesion (arrow) and wedge-shaped enhancement becoming isointense to healthy hepatic parenchyma.

View larger version (141K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 9. —45-year-old man with hepatocellular carcinoma and arteriosystemic shunt. A, Contrast-enhanced arterial phase CT scan shows hypervascular mass in right lobe of liver with early filling of dilated right hepatic vein (arrow), representing arteriosystemic venous shunting.

View larger version (133K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 9. —45-year-old man with hepatocellular carcinoma and arteriosystemic shunt. B, Portal venous-phase CT scan shows large hepatocellular carcinoma.

References

Top Introduction Portosystemic Venous Shunt Arterioportal Shunts Arteriosystemic Shunts References

 

1. Chen WP, Chen JH, Hwang JI, et al. Spectrum of transient hepatic attenuation differences in biphasic helical CT. AJR 1999:172:419-424[Free Full Text]
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3. Kim TK, Choi BI, Han JK, et al. Nontumorous arterioportal shunt mimicking hypervascular tumor in cirrhotic liver: two-phase spiral CT findings. Radiology 1998;208:597-603[Abstract/Free Full Text]
4. Park JH, Cha SH, Han JK, Han MC. Intrahepatic portosystemic venous shunt. AJR 1990;155:527-528[Free Full Text]
5. Mori H, Hayashi K, Fukuda T, et al. Intrahepatic portosystemic venous shunt: occurrence in patients with and without liver cirrhosis. AJR 1987;149:711-714[Abstract/Free Full Text]
6. Itai Y, Furui S, Ohtomo K, et al. Dynamic CT features of arterioportal shunts in hepatocellular carcinoma. AJR 1986;146:723-727[Abstract/Free Full Text]
7. Buscarini E, Buscarini L, Civardi G, Arruzzoli S, Bossalini G, Piantanida M. Hepatic vascular malformations in hereditary hemorrhagic telangiectasia: imaging findings. AJR 1994;163:1105-1110[Abstract/Free Full Text]
8. Kanazawa S, Niiya H, Mitogawa Y, Yasui K, Hiraki Y. Cavernous hemangioma with arterioportal and arterio-hepatic vein shunts coexisting with hepatocellular carcinoma. Radiat Med 1994;12:83-85[Medline]
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10. Shimokawa Y, Kubo Y, Arishima T, et al. Studies on primary liver carcinoma. III: Clinico-pathological characteristics of gross anatomy of hepatocellular carcinoma according to Nokashima-Okuda classification. Acta Hepatol (Japan) 1975;16:752-762

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