The portal vein and its tributaries
|Classification and external resources|
Portal hypertension is hypertension (high blood pressure) in the hepatic portal system, which are the portal vein and its branches, which draining from most of the intestines to the liver. Portal hypertension is defined as a hepatic venous pressure gradient equal to or greater than 6 mmHg. Cirrhosis (a form of chronic liver failure) is the most common cause of portal hypertension; other, less frequent causes are therefore grouped as non-cirrhotic portal hypertension. When it becomes severe enough to cause symptoms or complications, treatment may be given to decrease portal hypertension itself or to manage its complications.
Signs and symptoms
Signs and symptoms of portal hypertension include:
- Ascites (free fluid in the peritoneal cavity),
- Increased spleen size (Splenomegaly), which may lead to lower platelet counts (thrombocytopenia)
- Swollen veins of the oesophagus (Oesophageal varices), which may bleed and cause vomiting of blood (haematemesis)
- Swollen veins on the anterior abdominal wall (sometimes referred to as Caput medusae) 
- Hemorrhoids (swollen or dilated hemorrhoidal veins)
The causes for portal hypertension are classified as originating in the portal venous system before it reaches the liver (prehepatic causes), within the liver (intrahepatic) or between the liver and the heart (post-hepatic). The most common causes is cirrhosis (chronic liver failure). Other causes include:
|Conditions associated with non-cirrhotic portal hypertension|
|Prehepatic causes||Portal vein thrombosis or splenic vein thrombosis|
|Splenomegaly (increased portal blood flow)|
|Hepatic causes||Any cause of cirrhosis, e.g. alcohol abuse, chronic viral hepatitis, biliary atresia, etc.|
|Primary biliary cirrhosis|
|Primary sclerosing cholangitis|
|Hereditary haemorrhagic telangiectasia|
|Congenital hepatic fibrosis|
|Nodular regenerative hyperplasia|
|Fibrosis of space of Disse|
|Granulomatous or infiltrative liver diseases (Gaucher, mucopolysaccharidosis, sarcoidosis, lymphoproliferative malignancies, amyloid deposition, …)|
|Toxicity (from arsenic, copper, vinyl chloride monomers, mineral oil, vitamin A, azathioprine, dacarbazine, methotrexate, amiodarone, …)|
|Fatty liver disease|
|Posthepatic causes||Inferior vena cava obstruction|
|(Right-sided) heart failure, e.g. from constrictive pericarditis|
|hepatic vein thrombosis|
The pathophysiology of portal hypertension is indicated by increasing vascular resistance via different etiologies; additionally, stellate cells and myofibroblasts are activated. Increased endogenous vasodilators in turn promote more blood flow in the portal veins.
Nitric oxide is an endogenous vasodilator and it regulates intrahepatic vascular tone (it is produced from L-arginine). According to Maruyama, et al., in laboratory studies nitric oxide inhibition increases portal hypertension and hepatic response to norepinephrine is increased.
The diagnosis of portal hypertension can be done via HVPG (hepatic venous pressure gradient) measurement has been accepted as the gold standard for assessing the severity of portal hypertension. Portal hypertension is defined as HVPG greater than or equal to 5 mm Hg and is considered to be clinically significant when HVPG exceeds 10 to 12 mm Hg.
In clinical practice the pressure is not measured directly until the decision to take a liver biopsy for suspected cirrhosis (chronic liver failure), or to place a transjugular intrahepatic portosystemic shunt has been made. Part of the procedure, a hepatic vein wedge pressure is measured with the assumption of no pressure drop across the liver yielding portal vein pressure.[medical citation needed]
The treatment of portal hypertension is divided into:
Selective shunts select non-intestinal flow to be shunted to the systemic venous drainage while leaving the intestinal venous drainage to continue to pass through the liver. The most well known of this type is the splenorenal. This connects the splenic vein to the left renal vein thus reducing portal system pressure while minimizing any encephalopathy. In an H-shunt, which could be mesocaval (from the superior mesenteric vein to the inferior vena cava) or could be, portocaval (from the portal vein to the inferior vena cava) a graft, either synthetic or the preferred vein harvested from somewhere else on the patient's body, is connected between the superior mesenteric vein and the inferior vena cava. The size of this shunt will determine how selective it is.
It should be noted that with the advent of transjugular intrahepatic portosystemic shunting (TIPS), portosystemic shunts are less performed. TIPS has the advantage of being easier to perform and doesn't disrupt the liver's vascularity.
Prevention of bleeding
Both pharmacological (non-specific β-blockers, nitrate isosorbide mononitrate, vasopressin such as terlipressin) and endoscopic (banding ligation) treatment have similar results. TIPS (transjugular intrahepatic portosystemic shunting) is effective at reducing the rate of rebleeding.
This should be gradual to avoid sudden changes in systemic volume status which can precipitate hepatic encephalopathy, renal failure and death. The management includes salt restriction, diuretics (spironolactone), paracentesis, and transjugular intrahepatic portosystemic shunt.
A treatment plan may involve lactulose, enemas, and use of antibiotics such as rifaximin, neomycin, vancomycin, and the quinolones. Restriction of dietary protein was recommended but this is now refuted by a clinical trial which shows no benefit. Instead, the maintenance of adequate nutrition is now advocated.
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