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Thứ Sáu, 20 tháng 4, 2012

CDUS in Budd Chiari Syndrome

Download fulltext: http://onlinelibrary.wiley.com/doi/10.1111/j.1754-9485.2012.02341.x/full#f2#f2

Summary

Budd Chiari syndrome is an uncommon heterogeneous group of disorders which occur due to obstruction at any level from the hepatic venules to the junction of inferior vena cava and right atrium of heart which has significant morbidity and mortality. An early diagnosis of the disease is required for appropriate treatment. Due to the diffuse nature of the disease, normal biopsy findings do not exclude the disease. Proper clinical history and imaging are essential for definitive diagnosis. In this pictorial essay, we discuss the imaging spectrum of Budd Chiari syndrome.

Introduction

Budd Chiari syndrome (BCS) is a heterogeneous group of disorders characterized by hepatic venous outflow obstruction from the level of the hepatic venules to the junction of inferior vena cava (IVC) and right atrium of heart.1 It is an uncommon condition which has significant morbidity and mortality. It was originally described by Budd in the mid nineteenth century, and after 50 years Chiari described the classic triad of hepatomegaly, ascites and abdominal pain.2 An early diagnosis of the disease is required for appropriate treatment. Diagnosis is based on clinical evaluation and findings on imaging studies such as Color Doppler Ultrasonography (CDUS), Multidetector Computed Tomography (MDCT) and Magnetic Resonance angiography (MRA), and Digital Subtraction Angiography (DSA).

Etiopathogenesis
Hypercoagulable states are the most common cause of BCS.3 These include myeloproliferative disorders like polycythemia vera and essential thrombocytosis and prothrombotic conditions like factor V Leiden mutation, antiphospholipid antibody syndrome and antithrombin III deficiency. Other causes are oral contraceptive pills, pregnancy and neoplasms.2,3 For clinical manifestation of BCS, at least two hepatic veins should be thrombosed.4 Thrombosis of hepatic veins results in an increase in the sinusoidal pressure, sinusoidal dilatation and filtration of interstitial fluid that results in ascites. Decrease in portal perfusion results in hypoxic damage and centrilobular necrosis of liver parenchyma. Reperfusion injury with release of free oxygen radicals also contributes to hepatic damage and necrosis. Nodular regeneration is the predominant finding in the periportal area in a few months, followed by fibrosis and cirrhosis of liver.3,4 The caudate lobe has direct venous drainage to the IVC and hence undergoes compensatory hypertrophy.4,5 Portal vein thrombosis is seen in 10–20% of cases of BCS and may be due to slow blood flow and hypercoagulable state.1,4

Classification
BCS is classified according to the level of obstruction.5

  • Occlusion of the IVC with or without involvement of hepatic veins
  • Occlusion of major hepatic veins
  • Obstruction of the small centrilobular venules (considered by some as veno-occlusive disease)
However, veno-occlusive disease which is also known as sinusoidal obstruction syndrome should be considered separate from BCS. It occurs following high dose of chemotherapy, total body irradiation in patients of haematopoietic stem cell transplantation, and the primary site of injury is the sinusoidal endothelial cell.4,6 Thus, a simple classification in which BCS into three types based on lesions in the IVC and the hepatic veins is suggested.5,7

·     Type I: Lesions of the IVC
·       Type II: Lesions of the hepatic veins including two subtypes
 o          IIa – short segment occlusion (<4 cm)
 o          IIb – diffuse occlusion
·        Type III: Mixed type with lesions of the IVC and the hepatic veins.


Clinical features
Clinical manifestations of BCS include classic triad of hepatomegaly, right upper quadrant pain and ascites.2,3 Presentation of the disease can be fulminant, acute, subacute or chronic.3,5 Fulminant form of disease presents with hepatic encephalopathy within 8 weeks of development of jaundice.5 The acute form of BCS is characterized by pain in abdomen, tender hepatomegaly, rapidly worsening encephalopathy and ascites within a short duration of time. Subacute BCS is the most common type, presenting with insidious onset ascites.3 Chronic BCS presents with manifestations of end-stage liver disease, portal hypertension and cirrhosis. Duration of the illness is usually more than 6 months.8

Spectrum of CDUS imaging

CDUS of the liver is the modality of choice in suspected cases of BCS with sensitivity and specificity of 85% or greater.5 In acute BCS, B mode US shows enlarged and bulbous liver with heterogeneous echo texture due to haemorrhagic infarction. Intrahepatic venovenous collaterals are not seen.5
In subacute BCS, B mode US shows heterogeneous echo texture of liver, enlarged caudate lobe, atrophy or hypertrophy of other lobes, ascites and splenomegaly. The visualization of a caudate lobe vein ≥3 mm in diameter (Fig. 1) on greyscale sonography strongly suggests the diagnosis of BCS. Liver shows heterogeneous echo texture in chronic BCS. The contour of liver is irregular with presence of regenerative nodules.

Figure 1. B mode ultrasonography transaxial scan of liver showing enlarged caudate lobe with prominent draining vein (arrow).

Hepatic venous B mode findings include absence, stenosis, dilatation or irregularity of the hepatic veins, or their abnormal or absent junction with the IVC in both subacute and chronic BCS. CDUS studies show absent or reversed flow, high velocity flow at site of stenosis or loss of phasic variation in the hepatic veins. Intrahepatic (comma shaped) venous collaterals are typical of BCS and may constitute the ring sign on CDUS.1,9 Such collaterals are either intrahepatic veins that communicate with systemic vessels via sub capsular collaterals or vessels that shunt blood from the occluded hepatic veins to the patent hepatic veins, including inferior right hepatic vein (Fig. 2).5

Figure 2. B mode ultrasonogaphy transaxial scan of liver showing thrombosed proximal left hepatic vein (LHV) with distal part draining into the ostium of middle hepatic vein (MHV) via collateral (arrow). IVC, inferior vena cava; RHV, right hepatic vein.

Inferior vena cava should be simultaneously examined while evaluating a patient for BCS. On real time ultrasound (US), short segment stenosis of IVC is seen as an area of narrowing with loss of respiratory phasicity in distal IVC. There can be long segment narrowing due to compression by an enlarged caudate lobe. In case of BCS due to IVC involvement, CDUS can show reversed flow (Fig. 3a), uniphasic flow at the site of stenosis, no flow in IVC with thrombotic occlusion (Fig. 4a), turbulent flow, very slow flow or balanced bidirectional flow.10 The portal venous flow is slow, continuous or reversed which depends on development of portal hypertension.




Conclusion

BCS is an uncommon disease and usually presents with non-specific symptoms and signs. Thus radiological imaging plays an important role in its early diagnosis. CDUS is widely available in all institutions and allows a correct diagnosis of this syndrome. So it should be used as initial screening method in suspected cases of BCS. MDCT venography and MRA helps to evaluate IVC, hepatic veins and to plan subsequent endovascular management. DSA is the definitive method for diagnosis of BCS and is performed to provide guidance for interventional therapeutic approaches.

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