Editing Portal hypertension

Defined as portal pressure gradient > 5mm Hg

* Portal pressure gradient: the difference in pressure between PV and the hepatic veins
* Measuring the gradient:
** Best method - transfemoral hepatic vein catheterisation with a balloon tip catheter

== Aetiology ==

* Increased PV resistance
** Pre-sinusoidal
*** PV, splenic or SMV thrombosis
**** Most common pre-hepatic cause
**** If PV is thrombosed in the absence of liver disease, bypassing collateral vessels develop to restore portal perfusion - cavernomatous transformation of the portal vein
**** Isolated splenic vein thrombosis is usually caused by pancreatic inflammation or neoplasm - easily reversed by splenectomy alone
*** Idiopathic
*** Mass effect
*** Schistosomiasis
*** Primary biliary cirrhosis
*** Alcoholic central sclerosis
*** Endothelitis (liver rejection, radiation injury)
*** Arterioportovenous fistula (traumatic or Osler-Weber-Rendu)
*** Hyperdynamic splenomegaly (infectious or myelodysplastic)
*** Nodular regenerative hyperplasia
*** Congenital extra-hepatic PV occlusion
** Peri-sinusoidal
*** Cirrhosis 
**** Alcoholic cirrhosis - most common cause of portal HTN
***** Deposition of collagen in the space of Disse, and post-sinusoidal (regenerating nodules distorting small hepatic veins)
*** Congenital hepatic fibrosis
*** Cystic liver disease
*** Sarcoidosis
** Post-sinusoidal
*** Budd-Chiari
*** Veno-occlusive disease (sinusoidal obstruction syndrome)
*** Chronic passive congestion (nutmeg liver)
*** Mass effect

== '''Pathophysiology - two main factors''' ==

* Increased resistance to portal venous blood flow at the level of sinusoids
** Structural
*** Pre-hepatic
*** Hepatic - most common - disturbed architecture of the liver and perivascular fibrosis
*** Post-sinusoidal
** Dynamic
*** Increased hepatic vascular resistance caused by active vasoconstriction and reduced release of vasodilators from endothelial cells
*** Stellate cells and myofibroblasts can contract in response to vasoconstrictors, leading to dynamic changes
* Also hyperdynamic circulation i.e. increased splanchnic blood flow
** Increased portal inflow - increased release of splanchnic vasodilators (VEGF, NO, etc.), in turn because of increased shear stress and reduced effective arterial volume
** These mediators also cause systemic hypotension, vascular underfilling, expansion of plasma volume, and increased cardiac output -> which are all implicated in development of ascites
** In particular, peripheral vasodilation leads to activation of RAAS and subsequent sodium retention and expansion of volume, worsening the hyperdynamic circulation

== '''Diagnosis''' ==

* Gold standard is hepatic vein wedge pressures
* Secondary signs are splenomegaly, cirrhotic-appearing liver, and intra-abdominal varices, with marked cytopaenias

== '''Assessment''' ==

* Diagnosis of the underlying liver disease
* Estimation of functional hepatic disease
* Definition of portal venous anatomy and hepatic haemodynamic evaluation
* Identification of the site of UGIB, if present

== '''Complications''' ==

* Ascites
* Splenomegaly
* SBP
* Portal hypertensive gastropathy
* Hepatopulmonary syndrome
* Varices/portosystemic shunts
** See 'liver' under 'anatomy'
** Develop where the portal and systemic venous circulations are in close apposition
** Most clinically significant is between left gastric and short gastric veins to the azygos vein - results in oesophago-gastric varices
** Recanalised umbilical vein from left portal vein to the epigastric venous system (caput medusae)
** Retroperitoneal collaterals
** Haemorrhoidal venous plexus
** Intra-hepatic venous shunts can also develop via capillarized hepatic sinusoids
**
** Management of non-bleeding varices
*** See varices topic under UGIS
** Bleeding varices
*** See 'UGIB' topic
*** The single most life-threatening complication of portal HTN - responsible for about a third of deaths in cirrhotic patients. 
*** If endoscopy fails, TIPS/surgical shunt may be needed


== '''TIPS (Transjugular Intrahepatic Portosystemic Shunt)''' ==

* Covered metal stent between right hepatic and portal veins
* Rescue therapy for uncontrolled variceal bleeding after failed endoscopic management or rebleeding
* Corrects underlying problem of portal HTN
* Indications/contraindications - see full list at bottom
** Variceal bleeding 
*** Can treat the underlying cause of varices at expense of hepatic encephalopathy
*** TIPS is good for variceal bleeding refractory to medical/endoscopic treatment
** Ascites refractory to medical management - very effective
** Hepatic hydrothorax (>500mL of pleural fluid in a cirrhotic patient with no cardiopulmonary disease) non-responsive to medical management
** Hepatorenal syndrome that occurs secondary to an extravascular fluid shift (i.e. type 2 HRS)
** Hepatopulmonary syndrome
** Budd-Chiari syndrome - difficult placement - may require so-called DIPS (Direct Intrahepatic Portosystemic Shunt)
** Portal hypertensive gastropathy
* Basically shunting from portal vein to hepatic vein: 
** Percutaneous guidance of a wire from right internal jugular vein to right hepatic vein through hepatic parenchyma into a portal branch, then expandable covered stent inserted
** Most frequently right portal vein
* Preparation
** Confirm absence of portal vein thrombosis, via CT. also allows definition of anatomy.
** G+H
** Start anti-encephalopathic medication
** Check right atrial pressure (should be less than 20mmHg to avoid precipitating right heart failure with extra preload)
* Complications 
** Recurrent variceal bleeding
*** Likely TIPS restenosis or occlusion - needs diagnostic venogram or intervention
** Stenosis/thrombosis
** Bleeding
** Encephalopathy
** Sepsis
** Liver infarction/liver failure
** Ongoing portal HTN
*** Can consider placing a second TIPS

*

[[Category:Liver]]