[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Liver and gallbladder](https://durgical.com/en/general-pathology/areas/liver/) › Hepatic venous outflow obstruction

# Hepatic venous outflow obstruction

- Lesion

If blood cannot leave the liver, it swells, becomes painful and congested, and the cells near the central vein die.

Updated Nov 12, 2026

## Key points

- Budd-Chiari: thrombosis of two or more major hepatic veins; causes are myeloproliferative neoplasms (JAK2), PNH, pregnancy, oral contraceptives, inherited thrombophilia, tumours.
- Triad: hepatomegaly, abdominal pain, ascites.
- Sinusoidal obstruction syndrome (veno-occlusive disease): endothelial injury from chemotherapy before stem cell transplant or pyrrolizidine alkaloids ('bush tea').
- Nutmeg liver: dark congested centres and pale periportal areas, from right heart failure.
- Ischemic hepatitis (shock liver): very high aminotransferases with zone 3 necrosis that fall quickly.
- Centrilobular hemorrhagic necrosis = left-sided failure or shock plus right-sided congestion.

## What it is

Obstruction to outflow at the level of the hepatic veins (Budd-Chiari syndrome), the small terminal venules and sinusoids (sinusoidal obstruction syndrome) or the heart (right heart failure) causes centrilobular congestion, hepatomegaly and ascites. Low flow from shock adds centrilobular necrosis. Chronic congestion leaves the classic nutmeg liver and, in long-standing heart failure, cardiac sclerosis.

## Structure

- Acute: enlarged, tense, red-purple liver; centrilobular congestion and hemorrhage.
- Chronic: nutmeg pattern on cut surface; zone 3 fibrosis and sinusoidal dilation.

## Step by step

- Venous outflow is blocked or right atrial pressure rises.
- Sinusoids around central veins dilate and fill with red cells.
- Pressure and low oxygen injure zone 3 hepatocytes; they atrophy or die.
- Plasma leaks into the space of Disse and peritoneum: hepatomegaly and ascites.
- Persistent block: perivenular fibrosis, nodular regeneration, sometimes cirrhosis.

## Disorders of hepatic venous outflow

| Disorder | Level of block | Causes | Liver |
| --- | --- | --- | --- |
| [Budd-Chiari syndrome](https://durgical.com/en/conditions/budd-chiari-syndrome/) | Large hepatic veins or suprahepatic cava | Myeloproliferative neoplasms, PNH, pregnancy, contraceptives, tumours | Swollen red-purple liver, zone 3 congestion and necrosis |
| Sinusoidal obstruction syndrome | Sinusoids and terminal hepatic venules | Myeloablative chemotherapy, pyrrolizidine alkaloids | Zone 3 congestion, obliterated venules, necrosis |
| [Passive congestion](https://durgical.com/en/conditions/heart-failure/) | Heart | Right heart failure, constrictive pericarditis | Nutmeg liver; cardiac sclerosis if chronic |
| Ischemic hepatitis | Low inflow plus congestion | Shock, left heart failure | Centrilobular coagulative necrosis |

## Memory aid

Block the exit and the back rooms flood first: zone 3 fills with blood and its cells drown.

## Test yourself

Think of the answer, then tap the question to see it.

## Which hematologic disorders most often cause Budd-Chiari syndrome?

Myeloproliferative neoplasms such as polycythemia vera (often JAK2-mutated) and paroxysmal nocturnal hemoglobinuria.

## What is sinusoidal obstruction syndrome?

Toxic injury to sinusoidal endothelium that obliterates terminal venules, seen after myeloablative chemotherapy or pyrrolizidine alkaloid ingestion.

## What gives the nutmeg pattern of chronic passive congestion?

Dark red congested centrilobular regions alternating with paler, sometimes fatty, periportal parenchyma.

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## Connections

## Related 6

- [Hepatic inflow disorders: artery, portal vein, sinusoids](https://durgical.com/en/general-pathology/hepatic-inflow-disorders-artery-portal-vein-sinusoids/)
- [Portal hypertension](https://durgical.com/en/general-pathology/portal-hypertension/)
- [Hyperemia and congestion (the nutmeg liver, heart-failure cells)](https://durgical.com/en/general-pathology/hyperemia-and-congestion/)
- [Shock: types, stages and the organs it damages](https://durgical.com/en/general-pathology/shock-types-stages-and-the-organs-it-damages/)
- [Thrombosis and Virchow's triad](https://durgical.com/en/general-pathology/thrombosis-and-virchow-s-triad/)
- [Hypercoagulable states: inherited and acquired](https://durgical.com/en/general-pathology/hypercoagulable-states-inherited-and-acquired/)

## Related conditions 6

- [Budd-Chiari syndrome](https://durgical.com/en/conditions/budd-chiari-syndrome/)
- [Heart failure](https://durgical.com/en/conditions/heart-failure/)
- [Polycythaemia vera](https://durgical.com/en/conditions/polycythaemia-vera/)
- [Paroxysmal nocturnal haemoglobinuria](https://durgical.com/en/conditions/paroxysmal-nocturnal-haemoglobinuria/)
- [Inherited thrombophilia](https://durgical.com/en/conditions/inherited-thrombophilia/)
- [Hypovolaemic shock](https://durgical.com/en/conditions/hypovolaemic-shock/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Hepatic vein obstruction (Budd-Chiari): MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000239.htm) (MedlinePlus, US National Library of Medicine, 2026); [Hepatic ischemia: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000214.htm) (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/hepatic-venous-outflow-obstruction/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/hepatic-venous-outflow-obstruction/