Flashcards in Hepatology - Portal hypertension Deck (20):
What is portal hypertension?
Portal hypertension is characterised by prolonged elevation of portal venous pressure (normally 5-6mmHg). Clinically significant portal hypertension is present when the gradient exceeds 10 mmHg and risk of variceal bleeding increases over 12 mmHg.
What veins form the hepatic portal vein?
The portal vein is formed by the union of the superior mesenteric (from the gut) and the splenic vein (from the spleen) and carries blood to the liver. It accounts for 75% of vascular inflow to the liver, 25% is by the hepatic artery. Blood vessels enter the liver via the hilum (porta hepatis) and blood passes into the hepatic sinusoids via the portal tracts and leaves the liver through the hepatic veins to join the IVC. The normal portal pressure is 5-8mmHg.
What are the main sites of obstruction of the portal vein leading to portal hypertension?
The inflow of portal blood to the liver can be partially or completely blocked at a number of sites, leading to high pressure proximal to the site of obstruction and the diversion of blood into portosystemic anastamoses. The main sites of obstruction are:
1) Prehepatic - due to blockage of the portal vein BEFORE the liver
2) Intrahepatic - resulting from distortion of the liver architecture
3) Posthepatic - due to venous blockage outside of the liver (rare)
The MCC of portal hypertension is cirrhosis.
Give some examples of pre hepatic causes of portal hypertension
1) Portal vein thrombosis due to sepsis (umbilical, portal pyaemia)
- inflammation of the portal vein is most commonly due to acute appendicitis; air present in the portal vein from bacterial gas
- Polycythaemia vera
- HCC (tumour invasion into portal vein)
3) Secondary to cirrhosis
In these cases there is portal hypertension, splenomegaly and ascites but NO hepatomegaly.
Name some intrahepatic causes of portal hypertension
Intrahepatic pre sinusoidal:
- Congenital hepatic fibrosis
- Vinyl chloride
- Polycystic liver disease
- Nodular regenerative hyperplasia
- Metastatic malignant disease
- peliosis hepatis (sinusoidal dilation due to blood; caused by anabolic steroids or Bartonella henselae causing bacillary angiomatosis)
Intrahepatic post sinusoidal:
- Veno-occlusive disease (complication of bone marrow transplantation, collagen develops around venules)
Posthepatic causes of portal hypertension?
What are the clinical features of portal hypertension?
The only evidence of portal hypertension may be splenomegaly in a patient with chronic liver disease. A diagnosis of portal hypertension is unlikely if splenomegaly cannot be detected on USS. The spleen is rarely enlarged >5 cm below the left costal margin in adults.
Collateral vessels may be visible on the anterior abdominal wall and occasionally several radiate to the umbilicus to form caput medusae. The most important collateral vessels occur in the stomach and oesophagus, where they can cause severe bleeding.
Other clinical features include:
- ascites (due to renal sodium retention)
- hepatic encephalopathy
- Fector hepaticus results from portosystemic shunting of blood, which allows mercaptans to pass directly to the lungs
Where are the porto-systemic anastamoses located?
Portacaval anastomoses occur when there is reversed blood flow in portal hyper- tension. These lead to the development of oesophageal varices (via anastomoses of the left gastric vein [portal] and the azygous vein [systemic]), caput medusae (via anastomoses of the paraumbilical vein [portal] with the superficial veins of the anterior abdominal wall [systemic]), and hemorrhoids (via anastomoses of the superior rectal vein [portal] and inferior rectal [systemic] veins).
How is portal hypertension investigated?
Endocsopic examination of the upper GIT: used to check and detect varices
USS: can show splenomegaly and collateral vessels and may sometimes indicate the cause such as liver disease or portal vein thrombosis
CT and MRI angiography: can identify portal vein clot and hepatic vein patency
Thrombocytopaenia: common due to hypersplenism - platelet counts are usually 100
- leucopaenia occurs occassionally, but anaemia is more likely to be due to bleeding than hyperpslenism
Portal venous pressure measurements - not routinely needed but can distinguish sinusoidal from pre-sinusoidal forms
How common is variceal bleeding in patients with portal hypertension?
Most patients with cirrhosis will develop varices, but only 1/3 will go on to bleed from them. Bleeding is often massive and mortality can be as high as 50%. Bleeding usually occurs from varices near the gastro-oesophageal junction or in the stomach. Risk of bleeding within 2 yrs varies from 7% for small varices to 30% for large varices.
What is primary prevention of variceal bleeding?
If non-bleeding varices are identified at endoscopy, β-blocker therapy with propranolol (80–160 mg/day) or nadolol is effective in reducing portal venous pressure and preventing variceal bleeding. Prophylactic banding is also effective in patients that are unable to tolerate β-blockers.
Outline the management of acute variceal bleeding
This is similar to and follows the management of acute upper GI bleeding. Patients should be resuscitated and undergo urgent gastroscopy to confirm the diagnosis and exclude bleeding from other sites.
1) Resuscitate + prophylactic cephalosporin
- give Terlipressin or somatostatin for emergency control before endoscopy
2) Urgent endoscopy with sclerotherapy or banding
- if bleeding stops, assess for beta blockade, if contraindication/ intolerance use banding
- if early rebleeding:
repeat endoscopic therapy
---> if bleeding stops, see above
---> if bleeding continues try passing Sengstaken tube
3) TIPS (transjugular intrahepatic portosystemic shunt) is used if there is a second rebleed occurs after treatment
What endoscopic procedures are used to treat active variceal bleeding?
Endoscopic therapy is the first line treatment for bleeding varices and will stop bleeding in 80% of cases. The common endoscopic methods are band ligation (small elastic bands are placed over the varices) or sclerotherapy (injection of a sclerosant solution, e.g. ethanolamine, into the varices).
When is pharmacological treatment used in acute variceal bleeding?
Pharmacological treatment is used for emergency control of bleeding while waiting for endoscopy and in combination with endoscopic techniques. Terlipressin (a synthetic analogue of vasopressin) restricts portal inflow by splanchnic arterial constriction. It is given by i.v. bolus injection (2mg every 6 hours) and is contraindicated in patients with ischaemic heart disease. Somatostatin, an i.v. infusion of 250-500 micrograms/h lowers portal pressure by a similar mechanism to terlipressin but is less effective. It is used when there are contraindications to terlipressin.
When is a balloon tamponade used in variceal bleeds?
Balloon tamponade with a Sengstaken-Blakemore tube is used if medical or endoscopic treatment described above has failed or contraindicated, or if there is exsanguinating haemorrhage. The gastric balloon is inflated and pulled back against the gastro-oesophageal junction to prevent cephalad variceal blood flow to the bleeding point. It can have serious complications such as aspiration pneumonia, oesophageal rupture and mucosal ulceration. To reduce complications the airway should be protected and tube left in situ for not longer than 12 hours. It is removed immediately prior to endoscopy.
What is TIPS?
TIPS (transjugular intrahepatic portosystemic shunting) is used when there is a second rebleed after treatment. A metal stent is passed over a guidewire in the internal jugular vein. The stent is then pushed into the liver substance, under radiological guidance, to forma shunt between the portal and hepatic veins, thus lowering portal pressure.
What additional treatment is needed for patients with variceal bleeding?
Patients require high-dependency/ intensive care
unit nursing. Antibiotic prophylaxis, e.g. cefotaxime, is given to prevent infection, and reduce rebleeding and early mortality. Lactulose is given to prevent portosystemic encephalopathy, and sucralfate to reduce oesophageal ulceration, a complication of endoscopic therapy.
How are recurrent variceal bleeds treated?
Followinganepisodeofvariceal bleeding there is a high risk of recurrence (60–80% over a 2-year period), and treatment is given to prevent further bleeds (secondary prophylaxis). The main options are:
1) Oral propranolol (in a dose sufficient to reduce the resting pulse rate by 25%), lowers portal pressure, but some patients are intolerant of treatment because of side effects
2) Repeated courses of variceal banding at 2-weekly intervals until the varices are obliterated. Varices may recur so follow-up endoscopy is required
3) TIPS or occasionally a surgical portosystemic shunt is performed if endoscopic or medical therapy fails. Hepatic encephalopathy is a complication of both procedures. Liver transplantation should always be considered when there is poor liver function
How can heart failure contribute to portal hypertension?
Left sided and right sided heart failure can cause intrahepatic obstruction to blood flow by cause centrilobular haemorrhagic necrosis.
LHF decreases cardiac output, causing hypoperfusion of the liver ---> leads to ischaemic necrosis of hepatocytes located round the central venules (zone III).
RHF causes a backup of systemic venous blood into the central venules and sinusoids and portal vein.
Clinically this produces:
1) painful hepatomegaly with or without jaundice
2) increased serum transaminases caused by ischaemic necrosis
3) may progress to cardiac cirrhosis (fibrosis around central venules)