Budd-Chiari syndrome: imaging review
Abstract
Budd-Chiari syndrome (BCS), also known as hepatic venous outflow tract obstruction includes a group of conditions characterized by obstruction to the outflow of blood from the liver secondary to involvement of one or more hepatic veins (HVs), inferior vena cava (IVC) or the right atrium. There are a number of conditions that lead to BCS-ranging from hypercoagulable states to malignancies. In up to 25% patients, no underlying disorder is identified. Diagnosis of BCS is based on a combination of clinical and imaging features. A major part of the literature in BCS has been devoted to interventions; however, a detailed description of various imaging manifestations of BCS is lacking. In this review, we highlight the importance of various imaging modalities in the diagnosis of BCS.
Introduction
Budd-Chiari syndrome (BCS) comprises a heterogeneous group of conditions characterized by partial or complete hepatic venous outflow obstruction.1–3 There is an increase in hepatic sinusoidal pressure secondary to hepatic venous outflow obstruction. This results in portal hypertension and liver congestion. The latter leads to hypoxia and hepatocyte dysfunction.2, 3 If the obstruction is severe and not corrected timely, hepatocyte necrosis sets in. This finally progresses to hepatic fibrosis and cirrhosis.2, 3
There are several causes of BCS. The most common condition is an underlying hypercoagulable or a prothrombotic state.4–6 These include various congenital conditions (including protein C deficiency, protein S deficiency, antithrombin deficiency, factor V Leiden mutation), myeloproliferative disorders, paroxysmal nocturnal hemoglobinuria, pregnancy, oral contraceptive intake, antiphospholipid antibody, malignancy, and few other conditions.4–6 Secondary BCS comprises of the conditions like the extension of thrombus from the renal cell carcinoma or hepatocellular carcinoma as well as a direct mass effect by liver lesions including liver tumors and abscesses. No underlying condition is found in up to 25% patients.6 However, recent literature reports an identifiable cause in 90% patients due to the availability of testing for a greater number of gene mutations.4
The clinical presentation ranges from mild symptoms to fulminant liver failure with a majority of patients manifesting as chronic liver disease.7, 8 The type of clinical presentation is determined by the extent and acuteness of venous obstruction and the adequacy of the patent primary and collateral venous outflow pathways.9, 10 Imaging evaluations play an important role in the diagnosis and classification of the disease.11 This is particularly important as the presentation in some patients may be non-specific and imaging may provide the first clue to the underlying condition. The management in BCS is heavily dependent on the imaging findings.11 Besides, imaging plays a very crucial role of follow up in patients following shunt procedures as well as those on medical management.12
Classification of BUDD-CHIARI SYNDROME
BCS is classified based on the etiology, the site of obstruction as well as the duration of disease. According to etiology, it is classified into primary (obstruction due to endoluminal venous lesion-thrombosis, webs, endophlebitis) and secondary (lesion outside venous system-tumor, abscess, cyst). Two classifications have been proposed based on the site of obstruction.7, 9
Several investigators have classified BCS into fulminant, acute, subacute, and chronic; however, others tend to divide them into acute, subacute, and chronic.7, 9 Differentiation of acute, subacute, and chronic is mainly based on clinical features.
Tables 1–3 highlight the types of BCS.
| Type | Level of obstruction |
| I | Obstruction of IVC with or without secondary hepatic vein occlusion |
| II | Obstruction of major hepatic veins |
| III | Obstruction of the small centrilobular venules (considered by some as veno-occlusive disease) |
| Type | Level of obstruction |
| I | Hepatic vein obstruction or thrombosis without IVC obstruction or compression |
| II | Hepatic vein obstruction or thrombosis with IVC obstruction or thrombosis |
| III | Isolated hepatic venous webs |
| IV | Isolated IVC webs |
| Type | Duration |
| Fulminant | Present with hepatic encephalopathy within 8 weeks of development of jaundice |
| Acute | Short duration (<1 month), ascites, hepatic necrosis without formation of venous collaterals |
| Subacute | Insidious onset (1–6 months), ascites, minimal hepatic necrosis, and portal and hepatic venous collaterals |
| Chronic | (>6 months) Complications of cirrhosis in addition to findings in the subacute form |
Imaging features of BCS
Imaging features are mainly determined by the duration of disease, the number of hepatic veins (HVs) involved, and the degree of obstruction.13–17
The imaging features of different stages of BCS are illustrated in Figures 1–8.
Ultrasound changes in BCS: Abnormal hepatic veins that are not seen along their entire course and show slightly echogenic lumen (arrows, A). Short segment stenosis of the right hepatic vein (arrow, B). Echogenic right hepatic vein (arrow, C). Enlarged caudate lobe (arrow, D). BCS, Budd-Chiari syndrome.
Doppler findings in BCS: Dilated caudate lobe vein is seen in a patient with chronic BCS (arrow, A). Doppler ultrasound in another patient with chronic BCS shows marked extrinsic compression of IVC (arrow, B). Doppler ultrasound image in the same patient shows intrahepatic comma-shaped veno-venous collateral between the hepatic veins (arrow, C). Monophasic flow in right hepatic vein that shows normal color flow (arrow, D). BCS, Budd-Chiari syndrome; IVC, inferior vena cava.
CT findings in BCS: Axial CT image in a patient with subacute BCS shows non-opacified hepatic veins (arrows, A). In another patient with chronic BCS, the abnormal confluence of hepatic veins with IVC is seen on axial CT image (arrow, B). Venovenous and perihepatic collaterals are seen on axial CT in a patient with chronic BCS (arrows, C). Sagittal CT image shows short segment stenosis of IVC with azygous-lumbovetebral collaterals (arrows, D). BCS, Budd-Chiari syndrome; IVC, inferior vena cava.
CT findings in BCS: (A) Axial CT image in a patient with subacute BCS shows thrombosis of main portal vein seen as filling defect (arrow, A). Coronal CT image in a patient with acute BCS shows filling defect in the middle HV (arrow, B). Ascites is also seen (short arrows, A and B). Axial and coronal CT images in a patient with thrombosis of IVC seen as filling defect causing expansion of the lumen (arrows, C and D). BCS, Budd-Chiari syndrome; HV, hepatic veins; IVC, inferior vena cava.
Collateral pathways in BCS: Coronal CT image in a patient with chronic BCS shows dilated azygous vein draining the lumbovertebral veins (arrow, A). In another patient with chronic BCS, pericardiophrenic venous collaterals is seen on axial CT image (arrow, B). Also seen are dilated azygous (short arrow, B) and hemiazygous veins (arrow head, B). Abdominal wall venous collaterals (short arrows, C) draining the hepatic capsular veins (arrow, C) and markedly dilated tortuous epigastric collaterals (arrow, D) are seen in a patient with chronic BCS. BCS, Budd-Chiari syndrome.
MR findings in BCS: Axial T2W in a patient with subacute BCS shows heterogeneous signal intensity of the liver (arrow, A). Axial T2W image in the same patient at a different level shows caudate lobe enlargement (arrow, B). Axial T1W image shows nodular liver outline (arrows, C). Post-gadolinium image in the arterial phase shows heterogeneous enhancement of liver (arrow, D). BCS, Budd-Chiari syndrome; T1W, T1 weighted; T2W, T2 weighted.
MR findings in BCS: Axial contrast enhanced MR image in a patient with chronic BCS shows non-opacified hepatic veins (arrows, A). Axial and coronal contrast-enhanced MR images show filling defect in IVC (arrows, B and C). Non-opacified hepatic veins are seen in another patient with chronic BCS (arrows, D). BCS, Budd-Chiari syndrome; IVC, inferior vena cava.
MR findings in BCS: Heterogeneous signal intensity of the liver is seen on axial T2W and T1W images in a patient with subacute BCS (arrow, A and B). Enhancement of the caudate lobe with non-enhancing periphery is seen in the arterial phase axial MR image in the same patient (arrow, B). Also note tiny hyper-enhancing nodules in right lobe (short arrows, C) suggestive of nodular regenerative hyperplasia. In the venous phase in the same patient, there is some enhancement of the liver periphery (arrows, D). BCS, Budd-Chiari syndrome; T1W, T1 weighted; T2W, T2 weighted.
Acute BCS
In the acute form of BCS, patients present with a rapid development of upper abdominal pain, abdominal distension secondary to ascites and liver enlargement, renal failure, and jaundice.8, 18 The imaging features of acute BCS are discussed below and highlighted in Table 4.
| Modality | Findings |
| Ultrasound (Figure 1) | Liver is large and bulbous |
| Altered regional echogenicity (due to hemorrhagic infarction) | |
| Sparing of caudate lobe (emissary veins drain directly into IVC) with caudate hypertrophy | |
| Ascites | |
| CT (Figure 3) | Patchy, decreased peripheral enhancement caused by portal and sinusoidal stasis and stronger enhancement of the central portion of liver parenchyma |
| Caudate size ranges from normal to moderately increased | |
| Ascites | |
| MRI (Figures 4–6) | T1W-decreased signal intensity within liver periphery and preservation of more normal, higher SI within the central liver and caudate lobe |
| T2W-heterogeneously increased signal intensity in the peripheral portion of the liver and caudate lobe. | |
| Post-gadolinium images-increased enhancement within caudate lobe on arterial phase which persists on delayed phase images. Enhancement of liver periphery is heterogeneously decreased throughout early and late post-contrast sequences which persists on delayed phase images. |
Parenchymal changes
As a result of acute obstruction of hepatic venous outflow (attenuation/ thrombosis of HVs and/or IVC), there is hepatomegaly and ascites. Venous thrombosis leads to an elevation of sinusoidal pressure and delay or reversal of portal venous blood inflow. In the acute form, venous collaterals have not developed and hepatocellular necrosis occurs rapidly.11,13–17 The liver becomes non-homogeneous with delayed enhancement of periphery. The peripheral zones of the liver usually appear hypodense on contrast enhanced CT and hypointense on contrast-enhanced MRI in the arterial phase, which results from the increased post-sinusoidal pressure produced by hepatic venous obstruction. Caudate lobe demonstrates increased contrast enhancement compared with the remainder of the liver.18–20 The sparing of caudate lobe is explained by its separate venous drainage. In the portal venous phase, a “flip-flop” pattern ensues, with low attenuation of the central part of the liver because of washout, while attenuation in the peripheral part of the liver gradually increases with the accumulation of contrast material from capsular veins.14, 15 The caudate lobe enlargement is seen in 80–91% of all cases.16, 17
Vascular changes
A recent thrombus is hypoechoic on ultrasound and leads to expansion of the lumen of the involved HVs.17 It produces signal void on Doppler ultrasound. Over a few days, the thrombus becomes echogenic with retraction of the lumen of the involved hepatic veins.17, 21 On CT and MRI, filling defect is seen within the HVs seen as hypodensity (on CT) or hypointensity (on MRI).21–23 Stenosis is best detected with Doppler ultrasound as it allows interrogation of the hemodynamic effects of the stenosis in the form of color aliasing and a local increase in flow velocity.17 Directional alterations in flow may also be detected with Doppler. These changes are difficult to detect on CT or MRI.17 The vascular changes in acute BCS are discussed in detail in Table 5.
| Modality | Hepatic veins | IVC | Additional findings |
| Ultrasound (Figure 1) | Partial or complete inability to see hepatic veins | Narrowing due to compression by the enlarged caudate lobe | Caudate vein ≥3 mm in diameter strongly suggests the diagnosis in appropriate clinical setting.13 |
| Stenosis with proximal dilatation | Long segment narrowing without associated caudate lobe enlargement | ||
| Intraluminal echogenicity | Localized, marked narrowing consistent with a web | ||
| Thickened walls | Focal localized thrombus | ||
| Membranous web is seen as echogenic areas or focal obliteration of the lumen | |||
| An aneurysm may be seen in IVC | |||
| Color Doppler (Figure 2) | No flow in part or all hepatic veins | Partial IVC obstruction or extrinsic IVC compression leads to pseudoportal flow | Portal flow may be affected, is dampened or reversed. |
| Flow in the abnormal direction in part or all hepatic veins | |||
| High flow velocity is seen at the site of stenosis | |||
| Change in flow from phasic to absent, reversed, turbulent or continuous. | |||
| Continuous flow called “pseudoportal Doppler” signal | |||
| CT (Figure 3) | Thrombosed hepatic veins/IVC seen as filling defect (partial/complete) | IVC compressed by enlarged caudate lobe | |
| MRI (Figures 4–6) | Abnormal appearance of hepatic veins on T2W images | Extrinsic compression of the IVC | |
| Non-visualisation of hepatic veins | Filling defect | ||
| Non-opacification of one or more hepatic veins | Non-opacification | ||
| Filling defects within one or more hepatic veins | |||
| Focal stenosis of hepatic veins |
Subacute BCS
It is the most common clinical type of BCS. This form has an insidious onset and may take up to 3 months to become symptomatic.5, 6,24,25
Imaging features are characterized by volume redistribution as well as the development of collateral vessels.10–14 These changes overlap with those of chronic BCS and distinction between the two may not be possible based solely on imaging and clinical presentation needs consideration. These changes are discussed in detail in the section below and Table 6.
| Modality | Findings |
| Ultrasonography (Figure 1) | Enlargement of the caudate lobe with liver surface nodularity with hetero-echoic pattern of the peripheral liver parenchyma |
| Ascites | |
| CT (Figure 3) | Liver volume redistribution with a nodular surface |
| Heterogeneous enhancement of the peripheral liver in the early contrast enhanced phase with homogeneous attenuation in delayed phases | |
| Homogeneous enhancement of the enlarged caudate lobe | |
| MRI (Figures 4–6) | Preservation of normal signal intensity in the caudate lobe on all sequences Heterogeneously decreased SI within the peripheral liver on T1 weighted images and heterogeneously increased SI within the peripheral liver on T2 weighted images. |
| Post-contrast enhancement of caudate lobe is less prominent than the heterogeneously increased enhancement observed in the peripheral liver. Overall enhancement pattern becomes more homogeneous on more delayed imaging sequence. |
Chronic BCS
Parenchymal changes
In the chronic BCS there is bridging fibrosis from HV to portal tracts.26 In the chronic stage of BCS, there are features of chronic liver parenchymal disease. Parenchymal edema which was a prominent feature in the acute and subacute stage is not a prominent feature of chronic BCS.19, 25 Differential attenuation (on CT)/signal intensities (on MRI) observed in patients with acute and subacute stages of disease are more subtle in chronic stage. Differential enhancement pattern between center and periphery of the liver is also more subtle. Caudate lobe is markedly enlarged in chronic disease. Ascites, and collateral vessels are other ancillary findings (may also be seen in subacute stage) of chronic BCS.16, 17
Another typical feature is the development of regenerative nodules. These are usually multiple and range in diameter from 0.5 to 4 cm. Pathogenesis involves insufficient blood supply to the hepatocytes leading to atrophy. Compensatory nodular hyperplasia occurs in areas where blood supply is adequate.27 These regenerative nodules are predominantly supplied by arteries and hence show marked arterial hyperenhacement and may be sometimes difficult to differentiate from adenoma.28 Most of the lesions are likely to be reactive than neoplastic.29 Hepatocellular carcinoma can develop in patients with chronic BCS and accounts for 0.7% of all hepatocellular carcinoma.30
The parenchymal changes of chronic BCS are described in Table 7.
| Modality | Finding |
| Ultrasound (Figure 1) | Features of cirrhosis NRH nodules are iso-echoic and may be difficult to visualize |
| CT (Figure 3) | Regenerative nodules are multiple, ranging in size from 0.5 to 4 cm. |
| Multiphasic CT – nodules are homogeneous. Show marked arterial phase enhancement. Enhancement persists in portovenous phase.17 | |
| MRI (Figures 4–6) | Changes of fibrosis and chronic liver parenchymal disease. Regenerative nodules: T1 bright T2 isointense to hypointense Post-contrast – hypervascular in arterial phase, no washout in the venous phase |
Vascular changes
Direct evidence of venous thrombosis is not much appreciated in the chronic stage. There is the development of small, bridging intrahepatic and capsular hepatic venous collaterals. These are well developed in chronic, not seen in acute, and may be present to a lesser extent in subacute forms.16, 17Table 8 highlights the vascular changes in chronic BCS.
| Modality | Findings |
| Ultrasound Doppler (Figure 2) | Intrahepatic veno-venous collaterals – specific diagnosis. Seen as comma-shaped channels showing color flow |
| Intrahepatic collaterals – communicate with systemic vessels via subcapsular collaterals | |
| Collaterals from an occluded hepatic vein to a non-occluded hepatic vein | |
| Collaterals form occluded hepatic vein to caudate lobe veins | |
| Rarely from hepatic veins to suprahepatic IVC close to the right atrium. | |
| CT venography (Figure 3) | The diameter of the hepatic artery is enlarged compared to the splenic artery. |
| Multiple collateral channels as described above may be seen though less confidently | |
| MR venography (Figures 4–6) | Venous collateralization may be seen with the same or higher degree of sensitivity and specificity as the ultrasound Doppler |
| Venography | Spiderweb pattern of collateral vessels |
| Long segment compression of IVC caused by caudate lobe hypertrophy | |
| Thrombus within hepatic veins seen as filling defect | |
| Dilated hepatic artery with arterioportal shunts | |
| Thrombus in IVC |
Features of chronic liver disease and portal hypertension may develop. Portal vein and splenic veins are dilated. The paraumbilical vein is dilated. Multiple collaterals are seen in periportal, peripancreatic, near splenic hilum region.11 Esophageal and rectal varices may be seen. Besides, the collaterals that develop secondary to portal hypertension, the extrahepatic collaterals are a part of chronic BCS. The pattern of these extrahepatic collaterals is characteristic of BCS.17 These are discussed in detail in the section below.
Role of individual imaging modalities
Doppler ultrasound
Doppler ultrasound is the first line imaging study for evaluation of patients with BCS.17 The advantages of Doppler ultrasound are easy availability, cost-effectiveness, and lack of ionizing radiations. It has a sensitivity and specificity of 85% for the diagnosis of BCS.31 It allows accurate evaluation of the vascular changes including the cause, site, and the extent of the block (Figure 1). It also allows depiction of intrahepatic venovenous collaterals, a highly specific finding for BCS (Figure 2). Besides, it provides information about the blood flow direction and flow pattern.17 It is also fairly accurate in the demonstration of morphological changes in the liver as well as the demonstration of changes of portal hypertension. It is less accurate in mapping the extrahepatic collateral pathways and characterization of focal liver lesions in the setting of BCS.11 The limitations of Doppler ultrasound include operator dependence, technical difficulty posed by obesity and bowel gas, and inability to provide a reproducible roadmap for various endovascular and surgical interventions.32 It remains the imaging test of choice in follow up of patients with BCS.
CT
CT is one of the most widely performed imaging tests in patients with suspected BCS. It delineates the vascular abnormality, evaluates the hepatic morphological changes as well as allows mapping of the vascular anatomy prior to endovascular interventions or surgery.32 While CT is accurate in depicting the indirect signs of BCS, the venous abnormality (direct signs) may not be consistently and accurately depicted.17
Direct sign
The most common sign of BCS on CT is non-visualized HVs (Figure 3A).17 While undetectable HVs on CT are indicative of BCS, false positive or indeterminate results have been reported in 50% of cases.17 Acute HV thrombosis is seen as a filling defect within the HV, which is hypodense on CT (Figure 4).22 Thrombosis is more easily demonstrated during the acute phase because the involved HVs are distended. Direct identification of ostial stenosis is difficult on CT. Delayed hepatic parenchymal enhancement with HV dilatation may point towards ostial stenosis (Figure 3B).17 Concomitant portal vein thrombosis may be seen in up to 15% patients (Figure 4A).11
The initial studies reported CT to be a less sensitive modality in evaluation of IVC involvement in BCS. Lim et al compared the findings of ultrasound, CT, and catheter venography in the evaluation of patients with suspected membranous obstruction of IVC.33 15 patients were evaluated and CT was found to be less sensitive in detecting obliteration of intrahepatic veins and collateral vessels. Ultrasound was superior to CT in demonstrating the IVC membranes and in the depiction of the pathological hepatic venous anatomy.33 In another study, CT failed to detect IVC membrane in 23 patients.34 Zhang et al compared the performance of ultrasound and CT in the evaluation of BCS using surgical exploration as the reference standard.35 70 patients with BCS were evaluated. Ultrasound was significantly more accurate than CT in detecting membranous lesions of the inferior vena cava, hepatic vein openings, and short-segment lesions (thrombosis and fibrous tissue without the membrane). There was no significant difference between ultrasound and CT in the detection of long segment lesions of the hepatic veins.35
However, recent studies report good diagnostic performance of CT in BCS. Zhou et al compared image quality and anatomy delineation by CT venography under fixed or flexible delayed scan times in BCS patients with IVC obstruction.36 A total of 209 patients with BCS with IVC obstruction underwent either a CT venography study with a fixed delayed (180 s; n = 87) or a flexible delayed scan time according to IVC blood flow in color Doppler ultrasonography (n = 122). The flexible delayed scan time of CT venography allowed better detection and characterization of IVC obstruction compared to a fixed delayed scan time.36 High diagnostic accuracy has also been reported by Liu et al in 108 BCS patients with partial IVC obstruction who underwent CT venography.32 Virmani et al also reported an excellent correlation between CT venography and catheter venography in predicting the presence as well as grading the degree and length of IVC stenosis in 25 patients with BCS.37 IVC membranes were accurately depicted in all the patients (n = 4). CT has also been shown to be highly accurate in detection of HV abnormalities. In a study by Faraoun et al 171 patients with BCS with HV abnormalities with or without IVC abnormalities were evaluated using Doppler ultrasound, CT, and MRI.38 Perfect agreement amongst the three imaging modalities was reported for detecting long-standing HV thrombus. Slight to moderate agreement was reported for revealing the type of HV abnormality.
Indirect signs
CT is highly accurate in demonstrating the indirect signs of BCS. These include abnormal parenchymal enhancement, morphological alterations, abnormal perfusion, and intrahepatic and extrahepatic collaterals.17
Abnormal parenchymal enhancement
During the acute stage, the liver appears hypoattenuating and heterogeneous due to the predominance of venous congestion.17 There is a difference in the degree and timing of enhancement of central and peripheral liver. During the subacute and chronic stages of BCS, fibrosis sets in and leads to changes of cirrhosis. The heterogeneity persists and is more uniformly distributed while differences in the pattern of enhancement are more subtle.
Morphological alterations
During the acute stage, uniform hepatomegaly with a smooth liver outline is present.16 During the subacute and chronic stages, morphological alterations are typified by nodular outline and volume redistribution with atrophic and hypertrophic segments. Caudate lobe is markedly enlarged.
Perfusion abnormalities
Perfusion abnormalities are produced by elevation of sinusoidal pressure. These are visible during the portal venous phase in the acute stage as diffuse hyperattenuating areas or mosaic areas.39 The diffuse hyperattenuating areas are initially seen around the portal vessels. Later, these extend to the surrounding liver parenchyma. As the intrahepatic collateral vessels develop during the course of long-standing BCS, there is a hemodynamic balance between pre- and post-sinusoidal pressures and these hyperattenuating areas are no longer seen.17
Intrahepatic collaterals
This is a highly specific sign of BCS.17 The collaterals form in the chronic stage in an attempt to decongest the liver parenchyma. The veno-venous collaterals may form between two or more HVs, HVs and pericapsular veins, HVs and IVC, and HVs and veins of caudate lobe.40 CT is accurate in the depiction of veno-venous collaterals that are seen during the portal venous phase as comma-shaped enhancing channels bridging the vascular structures (Figure 3C). Sometimes, these channels may remain unenhanced due to the marked alteration in blood flow dynamics.
Extrahepatic collaterals
The pattern of extrahepatic collaterals in the setting of BCS is different from that seen in portal hypertension from other causes. The venous channels that drain the kidneys, diaphragm, vertebral plexus, and deep pelvic network form the extrahepatic collateral pathways in BCS (Figure 3C,D).41 They can be divided into three deep and one superficial venous pathway. The former allows the communication between IVC and the superior vena cava via the left renal vein (to hemiazygos vein), the lumbovertebral venous plexus (to azygos vein), and the phrenic vein (to pericardiophrenic vein) (Figure 5A,B).41 The superficial drainage pathway allows drainage of intrahepatic collaterals to veins of the chest and abdominal wall via hepatic capsular veins (Figure 5C,D). These channels include superior and inferior epigastric veins. CT allows adequate visualization of all the extrahepatic draining veins and in cases where the diagnosis of BCS is uncertain, the characteristic pattern of extrahepatic collaterals may suggest this diagnosis.
MRI
In some centers, MR venography is preferred over CT venography for the initial evaluation of patients suspected to have BCS. Besides, MR venography may be utilized as an adjunct to Doppler ultrasound in the assessment of patients with BCS. MRI is an excellent modality for the depiction of all the aspects of BCS including vascular changes, morphological changes, mapping of intrahepatic and extrahepatic collaterals, as well as characterization of liver nodules (Figures 6–8).17, 42 It is also useful in follow up of patients following endovascular or surgical interventions.
Catheter venography
Venography is useful in the assessment of the extent of outflow obstruction and also allows for pressure measurements.1 Also, endovascular interventions can be performed at the same sitting. It is however invasive, time-consuming, and needs expertise.43 It is usually not used for diagnosis alone except in situations where the results of other studies are equivocal or conflicting.
The diagnostic performance of various imaging techniques in BCS is highlighted in Table 9.
The dilemma in imaging of BCS (conditions mimicking diagnosis of BCS or posing potential problems in diagnosis of BCS)
- Chronic liver parenchymal disease: In chronic liver parenchymal disease, there is IVC pseudostenosis which may mimic BCS.44 There may be non-visualization of the hepatic vein near confluence which may lead to the false label of BCS.
- Obesity: one limiting factor in these patients is inadequate insonation of ultrasound waves.32 So there may be a diagnostic dilemma in these patients, particularly when the patient is being worked up for cryptogenic cirrhosis and imaging needs to rule out the possibility of BCS. These patients may undergo MR venography. However, MR venography may have its own limitations including claustrophobia, patients with aneurysmal clips, inability to hold breath which leads to degraded quality of images.
- The angle of insonation in Doppler: in author experience, 0o angle can be achieved only with the right hepatic vein. Angle can be achieved to a satisfactory level in middle hepatic vein. But due to the inherent angle of the left hepatic vein, appropriate Doppler angle may not be achieved which may lead to erroneous results and false interpretation.
- Unstable patients (fulminant/ acute BCS): Inability to hold breath which leads to diagnostic difficulties both in ultrasound Doppler and MR venography.
In author experience, contrast-enhanced ultrasound (Figure 9) is an important problem-solving tool in patients who are suspected to be having BCS clinically but there are issues with other imaging techniques as discussed above.
Contrast-enhanced ultrasound: Normal hepatic veins are seen as enhancing structures (arrows, A). Stenosis is seen at the junction of the middle-left hepatic vein and IVC in a patient with subacute BCS (arrow, B). BCS, Budd-Chiari syndrome; IVC, inferior vena cava.
Imaging-guided therapeutic maneuvers
Endovascular treatment is the most important therapeutic option in patients with BCS.45 Endovascular interventions include angioplasty, stenting, catheter-directed thrombolysis, and creation of transjugular intrahepatic portosystemic shunts (TIPSS).16, 45 Cross-sectional imaging including CT and MR venography play an important role in patient selection and treatment planning.11 If all HVs are occluded, angioplasty or stenting is not feasible while TIPSS may be considered. Short segment stenosis or occlusion are predictors of the success of angioplasty and stenting. Additional information sought on imaging prior to treatment planning includes the presence and size of intrahepatic venous collaterals, permeability of the IVC and intra and extrahepatic portal veins as well as the size of the caudate lobe vein and accessory right hepatic veins.11
Acute BCS
Catheter-directed thrombolysis
In acute BCS, radiological interventions allow thrombolysis of the involved HV.45 This can be achieved by using pharmacological agents. Mechanical thrombolysis may also be utilized to restore deteriorating liver function. Thrombolysis technique is determined by the age of the thrombus; pharmacological agents alone may be effective for a hyperacute thrombus while older thrombus may additionally require mechanical thrombolysis.45
TIPSS
TIPSS has been extensively studied and found to be effective in patients with chronic BCS.46, 47 Few studies have described its favorable results in the acute BCS. He et al reported the results of TIPSS in 91 patients including 14 with acute BCS. TIPSS was technically successful in 12 patients with a reduction of portosystemic pressure gradient to normal and significant improvement in the liver function and serum bilirubin.48 In another study by He et al comprising 37 patients with acute BCS, TIPSS was performed in 21 patients with 100% technical success.49 No major procedure-related complications were reported. There was a significant reduction in the portosystemic pressure gradient as well as serum bilirubin. However, in the study by Mancuso et al, out of the eight patients with acute BCS and hepatic failure who underwent TIPSS, deaths were reported in four patients soon after the TIPSS.50
Chronic BCS
Patients are categorized into two groups for planning interventions. Patients having membranous or short segment occlusion of HV/IVC are the ideal candidates for angioplasty with or without stenting (Figure 10).45 In general, balloon angioplasty is sufficient for short segment stenosis or occlusion. If there is residual stenosis following balloon angioplasty, stenting may be required.45 The patients in whom all the HV are replaced by intrahepatic collaterals are not suitable for angioplasty and require the creation of TIPSS (Figure 11).16
Inferior vena cava angioplasty and stenting: Venogram performed via transfemoral route shows lack of opacification of IVC. There is filling of multiple collaterals (arrows, A). Following balloon angioplasty, there is significant residual stenosis and stent is placed (arrows, B). Stent is seen in situ (arrows, C). Post-angioplasty and stenting venogram reveals normal opacification of the IVC (arrow, D). IVC, inferior vena cava.
TIPSS in a patient with subacute BCS: Axial CT image shows lack of opacification of the hepatic veins; IVC is normally opacified (arrow, A). Right portal vein is accessed via the right transjugular approach (arrow, B). A parenchymal tract is created (arrows, C). Venogram reveals the TIPSS tract (arrow, D). Post-procedure CT shows normal opacification of the TIPSS stent (arrow, E). BCS, Budd-Chiari syndrome; IVC, inferior vena cava; TIPSS, transjugular intrahepatic portosystemic shunts.
Post-treatment imaging
Follow-up imaging test of choice is ultrasound Doppler (Figure 12A–C). Morphologically, response to treatment is manifest in the form of a reduction in ascites and the size of caudate lobe.51 The demonstration of color flow along the entire length of stent/ shunt is critical.51 The whole length of the shunt may be difficult to visualize on Doppler because of body habitus and overlying bowel gas. In these cases, MR venography allows reliable assessment52 . The blockage may be seen as stenosis or filling defect (Figure 12D). Reversal of blood flow in portal vein serves as an indirect evidence of shunt patency.
Post-treatment imaging: Normal opacification of the mesocaval shunt (arrow, A) is seen on coronal MR venography image. Middle hepatic vein stent (arrow, B) on ultrasound. It shows aliasing (arrow, C) and increased flow velocity on Doppler ultrasound evaluation suggestive of the stenosis. Non-opacified meso-caval shunt in another patient on axial post-contrast MR image (arrow, D).
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