Budd–Chiari Syndrome with Patent Hepatic Veins on Imaging: Clinicoradiological Spectrum of Small Vessel Occlusion and Partial Thrombosis of Large Veins

Abstract

Budd–Chiari Syndrome (BCS) usually involves thrombosis or obstruction of major hepatic veins. However, a subset of patients can present with atypical features where hepatic veins appear patent on imaging. The authors present three such cases demonstrating either exclusive small hepatic vein involvement (SHV-BCS) or partial thrombosis of large veins. Despite patent hepatic veins on imaging, patients exhibited features of portal hypertension, with definitive diagnosis established via hepatic venography and transjugular liver biopsy. Two patients responded well to transjugular intrahepatic portosystemic shunt procedure with resolution of ascites, while one was managed conservatively. These cases underscore the diagnostic challenges posed by SHV-BCS and partial thrombosis of large hepatic veins and emphasize the importance of high clinical suspicion and invasive diagnostics in atypical presentations. Early recognition is crucial for timely intervention and favorable outcomes.

Keywords

Budd–Chiari syndrome - small vessel occlusion - hepatic veins

Introduction

Hepatic venous outflow tract is the anatomical and functional pathway by which blood exits the liver and returns to the systemic circulation. It plays a vital role in hepatic hemodynamics and comprises a hierarchically organized interconnected network of venous channels that collect blood from the liver lobules and ultimately drain into the inferior vena cava (IVC). Within the liver parenchyma, this network can be broadly classified into smaller intrahepatic veins and larger segmental hepatic veins.

The intrahepatic venous drainage begins at the lobular level, with the central (lobular) vein receiving blood from hepatic sinusoids ([Fig. 1]). This central vein drains into the intercalated vein, which subsequently empties into the interlobular (collecting) vein.[1] These finer venous structures converge into the right, middle, and left major hepatic veins that drain larger liver segments directly into the IVC.

Fig. 1 Schematic diagram showing the hepatic lobular architecture and pathway of blood circulation from the sinusoids to the small hepatic veins (created using biorender.com).

The central, intercalated, and interlobular veins—collectively referred to as the small hepatic veins (SHVs)—are typically not visualized on routine imaging modalities due to their diminutive size.[1] Any disruption or impediment to hepatic venous outflow anywhere from the SHVs to the cavoatrial junction results in Budd–Chiari syndrome (BCS), also known as hepatic venous outflow tract obstruction.

The clinical presentation of BCS varies widely and depends on both the extent and rapidity of hepatic venous outflow obstruction. In the appropriate clinical setting, imaging-based demonstration of hepatic vein obstruction is typically sufficient to establish the diagnosis. Most cases of BCS are believed to originate in the large hepatic veins, with subsequent secondary involvement of the smaller intrahepatic veins.[1] However, a small subset of patients may present with atypical forms of BCS, characterized either by isolated involvement of the SHVs or by partial obstruction of the major hepatic veins.[2] [3] [4] These forms often elude detection on standard imaging modalities and require histopathological confirmation via liver biopsy to establish a definitive diagnosis. Herein, we describe our experience with three cases of atypical BCS in which large hepatic veins were patent on imaging.

Case 1

A 49-year-old woman presented to our outpatient department with complaints of abdominal distension, persistent fatigue, and loss of appetite. She had been diagnosed with chronic liver disease and refractory ascites 3 years prior at another facility—based on imaging and liver function tests—and was receiving weekly large-volume paracentesis.

On examination, she exhibited tachycardia, pallor, and severe muscle wasting. Her abdomen was markedly distended with a fluid thrill. Laboratory tests showed significant anemia with hemoglobin at 5.2 g/dL (normal: 12–15 g/dL), thrombocytopenia with a platelet count of 60,000/µL (normal: 150,000–400,000/µL), and hyponatremia at 130 mEq/L (normal: 136–146 mEq/L). Liver function tests were abnormal, revealing low serum albumin (2.1 g/dL; normal: 3.5–5.0 g/dL) and elevated total bilirubin at 2.6 mg/dL (normal: 0.3–1.2 mg/dL), with direct bilirubin at 1.6 mg/dL. Abdominal ultrasound showed irregular, lobulated hepatic contours with gross ascites. Hepatic veins were patent but exhibited monophasic flow ([Fig. 2]). Ascitic fluid analysis revealed a serum-ascitic albumin gradient (SAAG) of 1.7 and high ascitic fluid protein levels (4.5 g/dL). Given the high SAAG, high protein ascitic fluid, and monophasic hepatic vein flow, BCS was suspected, and the patient was admitted for further evaluation.

Fig. 2 Doppler ultrasound image demonstrating patent middle hepatic vein with monophasic flow waveform.

Contrast-enhanced computed tomographic (CECT) scan of the abdomen showed a dysmorphic, heterogeneously enhancing liver. All the three native major hepatic veins appeared mildly attenuated but patent ([Fig. 3]).The right and main portal veins had eccentric, partially occlusive bland thrombi. No hepatic volume redistribution typical of BCS was noted; instead, the caudate lobe was atrophied. An echocardiogram ruled out cardiac causes of posthepatic portal hypertension.

Fig. 3 Axial (A) and coronal (B) images from the contrast-enhanced computed tomographic (CECT) scan of abdomen showing attenuated but patent hepatic veins (solid arrows) with irregular, lobulated hepatic outlines.

Following a multidisciplinary team discussion, a hepatic venogram was performed, followed by a transjugular liver biopsy (TJLB) to conclusively rule out BCS and assess for hepatic fibrosis or cirrhosis. The venogram from the proximal right hepatic vein (RHV) showed a patent, normal-sized vessel. However, the catheter could not be advanced beyond the proximal-middle junction of the RHV and became wedged. Venography from this point revealed a characteristic spider-web pattern of intercalating SHVs within the liver parenchyma, consistent with BCS ([Video 1]; [Fig. 4]).

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Video 1 Video showing patent proximal right hepatic vein with a spider-web pattern of vasculature from the wedged position.

Fig. 4 Digital subtraction angiographic (DSA) image showing patent short segment of the right hepatic vein (arrow) near its confluence with the inferior vena cava. However, the distal part of the right hepatic vein is thrombosed with presence of a spider-web pattern of collaterals on venogram.

Liver biopsy specimen demonstrated hepatocyte loss with fibrosis and hemorrhage, focal regenerative nodules, sinusoidal congestion, and surrounding fibrosis ([Fig. 5]). To identify the cause of BCS, a hematological workup was conducted, including tests for factor V Leiden mutation, JAK2 mutation, and protein C and S deficiencies—all of which were negative or within normal limits. A bone marrow biopsy to rule out myeloproliferative neoplasms was also unremarkable.

Fig. 5 Representational liver histopathology of the patient with Budd–Chiari syndrome due to partial thrombosis of hepatic veins: (A, hematoxylin and eosin, 5 × ) Large areas of parenchymal loss (arrows) with extensive hemorrhage (arrowheads), scattered thin-walled vessels, and regenerative nodules (dashed arrow) with sinusoidal congestion; (B, hematoxylin and eosin, 10 × ) Extensive areas of hepatocyte loss with broad fibrosis, severe hemorrhage (arrowheads), and many scattered thin walled vessels; (C, hematoxylin and eosin, 10 × ) Focal areas of regenerative nodules with patchy sinusoidal congestion (arrow) and adjacent areas of bleed; (D, hematoxylin and eosin, 20 × ) Regenerative nodules of hepatocytes with sinusoidal dilatation (arrows).

Given the refractory ascites, the patient underwent transjugular intrahepatic portosystemic shunt (TIPS) to relieve portal hypertension. She tolerated the procedure well and was discharged after 7 days. Anticoagulation therapy with unfractionated heparin was initiated during the procedure, transitioning to low-molecular-weight heparin to prevent thrombotic stent occlusion. At discharge, she was prescribed apixaban (2.5 mg twice daily) and scheduled for follow-ups every 3 months with Doppler studies and laboratory tests.

Her ascites resolved within a week postprocedure, and liver function tests normalized within a month. She has remained asymptomatic during 30 months of follow-up with a patent TIPS stent.

Case 2

A 32-year-old man from Kazakhstan was referred to our institute with complaints of abdominal distension persisting for the past 3 months. Physical examination was largely unremarkable, except for a markedly distended abdomen with a fluid thrill.

Laboratory investigations revealed an elevated total bilirubin of 2.1 mg/dL (normal range: 0.3–1.2 mg/dL) with a direct bilirubin fraction of 1.4 mg/dL. Abdominal ultrasound showed gross ascites without any other significant findings.

Ascitic fluid analysis indicated a high SAAG of 1.4 and elevated ascitic fluid protein levels of 2.9 g/dL. A CECT scan of the abdomen demonstrated mottled, heterogeneous peripheral liver enhancement on portal venous phase. However, all three major hepatic veins appeared patent on the delayed phase images ([Fig. 6]).

Fig. 6 Axial (A, B) and sagittal (C) contrast-enhanced computed tomographic (CECT) images of the abdomen demonstrating heterogeneous, mottled enhancement of the peripheral liver parenchyma (arrowheads in A) with ascites. All the three major hepatic veins, however, appear patent on the delayed phase images (arrowheads in B, C, and solid arrow in C).

Considering the high SAAG, high protein ascitic fluid, deranged liver functions, and heterogeneous liver enhancement, BCS was suspected. Hepatic venography showed a patent, normal-sized proximal RHV. However, the catheter could not be advanced deeper into the RHV and became wedged. Venography from this point revealed a coarse network of interlacing veins within the liver parenchyma, characteristic of BCS ([Fig. 7]).

Fig. 7 Spider-web pattern of intercalating small intraparenchymal hepatic veins seen on wedge hepatic venogram.

This was followed by a TJLB, which revealed sinusoidal distention, hepatocellular loss, and centrilobular hemorrhage. A comprehensive hematological workup and bone marrow biopsy were performed to identify any hereditary or acquired prothrombotic conditions or myeloproliferative disorders, but all tests were negative.

The patient subsequently underwent a TIPS procedure to relieve portal hypertension. His ascites resolved and liver function tests normalized within 2 weeks postprocedure. He has remained asymptomatic during 18 months of follow-up.

Case 3

A 65-year-old man presented to our outpatient department for evaluation and management of liver cirrhosis, which had been diagnosed elsewhere 1 month prior based on ultrasound findings. He had a known history of polycythemia vera and was undergoing periodic phlebotomy.

At presentation, he was dyspneic at rest, while the remainder of the physical examination was unremarkable. Laboratory investigations were within normal limits. Two-dimensional shear wave elastography (Resona i9, Mindray) indicated features consistent with F2 fibrosis. A CECT of the abdomen showed a dysmorphic liver with irregular, lobulated margins and left lobar hypertrophy. The hepatic veins appeared patent, and no significant focal lesions were identified in the liver ([Fig. 8]).

Fig. 8 Axial contrast-enhanced computed tomographic (CECT) image of the abdomen demonstrating dysmorphic liver parenchyma with a patent right hepatic vein (arrow).

During the hospital stay, his dyspnea worsened. Cardiological and pulmonological evaluations suggested severe hepatopulmonary syndrome (HPS). Given the absence of cirrhotic features on elastography and negative etiological workup for liver cirrhosis, noncirrhotic portal hypertension was suspected.

Venography of the RHV showed a widely patent vessel in its entire length ([Fig. 9A]). However, the wedged hepatic venogram revealed a beaded appearance of small intraparenchymal hepatic veins ([Fig. 9B]) with a spider-web pattern of collateralization. The hepatic venous pressure gradient (HVPG) was mildly elevated at 8 mm Hg.

Fig. 9 Digital subtraction angiographic (DSA) images showing patent right hepatic vein on free venogram (A), while on wedge venogram (B) beaded appearance (arrows) of small hepatic veins is seen.

Liver biopsy demonstrated hepatocyte loss with fibrosis and hemorrhage, focal regenerative nodules, sinusoidal congestion, and surrounding fibrosis suggestive of BCS.

For symptomatic relief of HPS, TIPS was recommended. However, the patient declined the procedure due to financial constraints. He was initiated on symptomatic medical management for HPS and anticoagulation therapy to prevent progression of BCS.

The patient has been under follow-up for the past 9 months, with a fluctuating course of dyspnea.

Discussion

SHV-BCS refers to obstruction localized to the microvasculature within the hepatic lobules, primarily and exclusively affecting the SHVs.[2] [3] [4] This results in sinusoidal congestion, most prominently in the centrilobular (pericentral) region, and is accompanied by hepatocyte necrosis, fibrosis, and slowly progressive hepatic functional impairment. Sustained elevation in sinusoidal pressure eventually gives rise to the clinical features of portal hypertension.

Although SHV-BCS is infrequently reported, limited case studies and small series have identified paroxysmal nocturnal hemoglobinuria as a frequent underlying cause.[2] [3] Clinically, SHV-BCS presents with features of mild portal hypertension such as ascites and variceal bleeding.[2] However, case 3 in our series exhibited an atypical presentation characterized by dyspnea. While HPS has been documented in patients with classical BCS, to our knowledge, it has not been previously reported in association with SHV-BCS.[5]

Imaging in these patients typically show patent large hepatic veins and IVC. No direct evidence of venous obstruction is visualized in small veins due to their size limitations on imaging. However, there may be other findings like heterogeneous enhancement of hepatic parenchyma, delayed opacification of the hepatic veins, caudate lobe hypertrophy, and signs of portal hypertension that may point toward the diagnosis. In such a scenario, other hepatic sinusoidal disorders like veno-occlusive disease (also called sinusoidal obstruction syndrome), perisinusoidal disease, and infiltrative pathologies need to be excluded based on clinical history and presentation.[6]

Liver biopsy is required for definitive diagnosis of SHV-BCS. Histopathological findings include thrombosis or fibrosis of small hepatic venules, centrilobular sinusoidal dilatation and congestion, hepatocyte dropout or necrosis, and variable degrees of perivenular fibrosis and regenerative changes.[4]

Although liver biopsy confirmed the diagnosis of SHV-BCS in case 3 of our series, the venographic findings are noteworthy. The free hepatic venogram demonstrated a patent large hepatic vein; however, the wedge venogram revealed a beaded appearance of the small intraparenchymal hepatic veins—an observation not previously reported.

The therapeutic approach in symptomatic patients with SHV-BCS broadly aligns with established management principles for classical BCS. Initial steps include identification and treatment of the underlying etiology. Anticoagulation should be promptly initiated to mitigate the risk of further thrombotic events, particularly in patients with underlying hypercoagulable conditions. Supportive management is essential to control ascites, hepatic insufficiency, and features of portal hypertension. The role of TIPS in SHV-BCS has been described in limited reports and generally yields favorable results.[4] In cases of progressive hepatic decompensation or end-stage liver disease, liver transplantation may be warranted as a definitive therapeutic option.

An important extension of SHV-BCS is the partial involvement of the major hepatic veins, as demonstrated in cases 1 and 2 of our series. These patients may present with chronic, treatment-resistant ascites, often unresponsive to standard medical therapy. The clinical course in such scenarios is typically indolent, which contributes to delayed recognition and increases the risk of undertreatment if not identified early. Unlike classical BCS, where hepatic veins are typically occluded in their entire length, patients with partial large vein involvement frequently exhibit patent yet attenuated hepatic veins showing delayed opacification on cross-sectional imaging.

It remains a subject of debate whether SHV-BCS, partial occlusion, and complete thrombosis of the major hepatic veins represent three distinct subtypes or sequential stages within the disease spectrum.[2] While the latter interpretation is more commonly accepted, case 1 in our cohort—who exhibited longstanding symptoms of portal hypertension for over 3 years without complete large vein occlusion—highlights the variability in the rate of progression of thrombotic involvement and the fact that patient can become symptomatic at any stage. This underscores the need for a high index of suspicion and timely evaluation to facilitate early diagnosis and appropriate management.

Conclusion

SHV-BCS highlights the importance of maintaining clinical suspicion despite normal hepatic vein on imaging, particularly in patients with prothrombotic conditions who develop unexplained hepatic dysfunction or features of portal hypertension. Transjugular hepatic venography combined with liver biopsy is frequently necessary to establish a definitive diagnosis. TIPS serves as an effective intervention for alleviating portal hypertensive symptoms in such patients.

Conflict of Interest

None declared.

• References

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• 3 Gioia S, De Santis E, Cerbelli B. et al. Small hepatic veins Budd-Chiari syndrome and paroxysmal nocturnal hemoglobinuria - the association of two rare entities: a case report. Pathologica 2020; 112 (02) 102-104
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Publication History

Article published online:
15 October 2025