[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/) › Portal hypertension

# Portal hypertension

- Mechanism

If blood cannot pass through the liver, pressure backs up into the gut veins, causing fluid in the belly, varices and a big spleen.

Updated Nov 12, 2026

## Key points

- Four consequences: ascites, portosystemic shunts (varices), congestive splenomegaly, hepatic encephalopathy.
- Shunt sites: esophagogastric varices (left gastric to azygos), rectal (hemorrhoidal), periumbilical (caput medusae), retroperitoneal.
- Variceal bleeding is the most dangerous complication and a leading cause of death in cirrhosis.
- Schistosomiasis causes presinusoidal portal hypertension with pipe-stem (periportal) fibrosis and preserved liver function; it is important in parts of Latin America.
- Nitric oxide-driven splanchnic vasodilation raises portal inflow and lowers effective blood volume.
- Hypersplenism lowers platelets: thrombocytopenia is a common clue to cirrhosis.

## What it is

Portal hypertension is raised pressure in the portal venous system. Resistance can be before the liver (portal vein thrombosis), inside it (cirrhosis, schistosomiasis, sinusoidal obstruction) or after it (hepatic vein obstruction, right heart failure). Cirrhosis is by far the most common cause. Raised resistance combines with increased portal inflow from splanchnic vasodilation to produce ascites, portosystemic shunts, congestive splenomegaly and hepatic encephalopathy.

## Structure

- Varices: dilated tortuous submucosal veins of the distal esophagus and gastric cardia.
- Spleen: enlarged, firm, with congested red pulp, fibrosis and sometimes Gamna-Gandy bodies (iron and calcium deposits).

## Step by step

- Scar, regenerating nodules and contracted stellate cells raise intrahepatic resistance.
- Sinusoidal endothelium makes less nitric oxide and more vasoconstrictors, adding resistance.
- Splanchnic arteries dilate (nitric oxide and other mediators), so more blood enters the portal system.
- Portal pressure rises; collateral veins open between portal and systemic circulations.
- Fluid leaks from sinusoids into the peritoneum, worsened by low albumin and sodium retention: ascites.
- Spleen congests and enlarges, trapping platelets; gut toxins bypass the liver: encephalopathy.

## Where the block is

| Level | Examples | Point to remember |
| --- | --- | --- |
| Prehepatic | Portal vein thrombosis, splenic vein thrombosis, extrinsic compression | Liver itself may be normal; ascites less common |
| Intrahepatic presinusoidal | Schistosomiasis, portal-tract fibrosis, nodular regenerative hyperplasia | Liver function usually preserved |
| Intrahepatic sinusoidal | Cirrhosis of any cause | The most common cause |
| Intrahepatic postsinusoidal | Sinusoidal obstruction syndrome | Zone 3 congestion and necrosis |
| Posthepatic | Budd-Chiari syndrome, constrictive pericarditis, right heart failure | Large tender liver with congestion |

## Clinical notes

- Hematemesis from varices, abdominal distension from ascites, splenomegaly, confusion.
- Ascites can become infected without an obvious source: spontaneous bacterial peritonitis.

## Memory aid

A jammed liver acts like a blocked drain: water floods the yard (ascites), pipes swell around it (varices), the tank upstream bulges (spleen), and dirty water bypasses the filter (encephalopathy).

## Test yourself

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

## Which portosystemic anastomosis causes life-threatening bleeding in portal hypertension?

The esophagogastric one (left gastric vein to azygos system), which forms varices of the distal esophagus and gastric cardia.

## Why does schistosomiasis cause portal hypertension with good liver function?

Eggs trapped in portal venules cause periportal pipe-stem fibrosis: the block is presinusoidal and the parenchyma is largely spared.

## What links portal hypertension to thrombocytopenia?

Congestive splenomegaly sequesters platelets (hypersplenism); low thrombopoietin from the failing liver adds to it.

## What are the four main consequences of portal hypertension?

Ascites, portosystemic shunts with varices, congestive splenomegaly and hepatic encephalopathy.

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## Elsewhere in DurgiPedia

- [Splanchnic and portal circulation](https://durgical.com/en/physiology/splanchnic-and-portal-circulation/)

## Connections

## Related 6

- [Cirrhosis: morphology](https://durgical.com/en/general-pathology/cirrhosis-morphology/)
- [Liver failure: acute, chronic and acute-on-chronic](https://durgical.com/en/general-pathology/liver-failure-acute-chronic-and-acute-on-chronic/)
- [Hepatic inflow disorders: artery, portal vein, sinusoids](https://durgical.com/en/general-pathology/hepatic-inflow-disorders-artery-portal-vein-sinusoids/)
- [Hepatic venous outflow obstruction](https://durgical.com/en/general-pathology/hepatic-venous-outflow-obstruction/)
- [Liver infections: bacterial, fungal and parasitic](https://durgical.com/en/general-pathology/liver-infections-bacterial-fungal-and-parasitic/)
- [Edema and effusions: the four mechanisms](https://durgical.com/en/general-pathology/edema-and-effusions-the-four-mechanisms/)

## Related conditions 8

- [Portal hypertension](https://durgical.com/en/conditions/portal-hypertension/)
- [Cirrhosis](https://durgical.com/en/conditions/cirrhosis/)
- [Ascites and spontaneous bacterial peritonitis](https://durgical.com/en/conditions/ascites-and-spontaneous-bacterial-peritonitis/)
- [Upper gastrointestinal bleeding](https://durgical.com/en/conditions/upper-gastrointestinal-bleeding/)
- [Schistosomiasis](https://durgical.com/en/conditions/schistosomiasis/)
- [Portal vein thrombosis](https://durgical.com/en/conditions/portal-vein-thrombosis/)
- [Budd-Chiari syndrome](https://durgical.com/en/conditions/budd-chiari-syndrome/)
- [Hepatic encephalopathy](https://durgical.com/en/conditions/hepatic-encephalopathy/)

## Microorganisms 1

- [Schistosoma mansoni / S. haematobium / S. japonicum](https://durgical.com/en/microbiology/schistosoma-mansoni-s-haematobium-s-japonicum/)

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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: [Portal Hypertension](https://www.ncbi.nlm.nih.gov/books/NBK507718/) (StatPearls (NCBI Bookshelf), 2025); [Bleeding esophageal varices: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000268.htm) (MedlinePlus, US National Library of Medicine, 2026).

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