Makindo Medical Notes.com

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About

• Normal Portal Pressure is about 2-5 mmHg and in Portal Hypertension this rises to 12 mmHg and above.

Anatomy

• The causes can be separated anatomically. If one remembers the portal system is made up of the venous drainage from the GI tract. If you remember your anatomy you will recall that the inferior mesenteric vein joins the splenic vein.
• The splenic vein then joins with the superior mesenteric vein to form the portal vein. The portal vein enters the liver and feeds into the liver sinusoids. From this, the venous blood supply then passes to the IVC through the hepatic vein.
• The usual gradient across the liver venous outflow from the portal vein to the hepatic vein is usually 3 mmHg. This is the wedged hepatic venous pressure. Portal hypertension leading to bleeding occurs when the pressure is > 12 mmHg

Causes

• Pre sinusoidal Extrahepatic usually due to Portal vein thrombosis, Sepsis, Surgery, Pro coagulopathy, Abdominal trauma/surgery, Malignancy, Pancreatitis, Congenital
• Intrahepatic pre sinusoidal : Schistosomiasis, Sarcoidosis, Congenital hepatic fibrosis, Vinyl chloride, Drugs
• Sinusoidal: Cirrhosis, Malignancy, Cystic disease
• Intrahepatic post sinusoidal : Veno-occlusive disease
• Extrahepatic post sinusoidal: Budd-Chiari syndrome

Aetiology

• As with any system of flow the Portal pressure is proportional to flow x resistance. The causes are shown below
• The main component in Portal hypertension is increased resistance.
• There is compensatory portosystemic circulation set up so that most of the portal blood supply goes directly into the systemic circulation.
• Across the world the main cause is schistosomiasis which causes Portal hypertension but without liver failure.

Clinical

• Splenomegaly is the classic finding of portal hypertension and would be very unusual not to be present. Splenomegaly can be diagnosed clinically and confirmed by USS.
• Cruveilhier-Baumgarten disease where there is a patent umbilical vein that acts as a portosystemic shunt in a patient with underlying cirrhosis causing a venous hum over the liver or at the xiphisternum.
• The venous hum is known as the Cruveilhier-Baumgarten sign. Interestingly allegedly ascites does not occur in the classical syndrome. In Portal Hypertension varices occur in the lower oesophagus and also at the anus and may be mistaken for haemorrhoids.

Investigations

• Hypersplenism with reduced platelet counts of about 50-100 x10⁹/L. There may also be some mild leucopenia.