portal hypertension
HISTORY
The Egyptians recognized an association between liver disease and ascites. This complication of portal hypertension has been frequently documented in the Middle Ages. The first bleeding varices, confirmed by autopsy, was described in 1840 by Power, who did not recognize the liver. In a series of 60 autopsies in 1900, Preble established the relationship between cirrhosis, varices and gastrointestinal bleeding. The term portal hypertension was first used by Gilbert and Villaret in 1906.
PATHOPHYSIOLOGY
Portal hypertension is a serious complication of cirrhosis, contributing to some of the complications of chronic liver disease.
The portal vein is derived from the splenic vein and superior mesenteric vein and inferior. So get the blood that drains the splanchnic circulation to the liver. The liver is the major site of resistance to portal venous flow and acts as a vascular network extendable low resistance. The portal venous pressure is usually low (5-10 mmHg) and portal hypertension defined as greater than 10 mmHg.
Changes in portal pressure in the system are governed by Ohm's Law, which states that changes in pressure (P1-P2) in a vessel depends on the interaction between blood flow (Q) and vascular resistance (R).
(P1-P2) = Q x R
The increase in portal resistance can occur anywhere along the venous system, ie in the portal vein or its tributaries before the blood reaches the liver (prehepatic obstruction) in the vascular spaces within the liver (intra-obstruction liver) or after (post-hepatic obstruction). The intra-hepatic obstruction, in turn, is much more complex. Occlusion of small portal branches within the portal triad (pre-sinusoidal obstruction may complicate liver diseases where there is extensive infiltration or fibrosis inflammatory portal and peri-portal. Alternatively, blood flow can be prevented by narrowing of the sinusoids by collagen deposition or occlusion by the same cellular contractile elements (sinusoidal obstruction). Finally, the portal venous flow can be prevented at the terminal hepatic venules, due to occlusion induced by toxins (post-sinusoidal obstruction).
Causes of portal hypertension
Pre-hepatic obstruction
Splenic vein thrombosis
Portal vein thrombosis
Obstruction, intrahepatic;
Pre-sinusoidal schistosomiasis, sarcoidosis, congenital hepatic fibrosis
Sinusoidal fibrosis, alcoholic sickling crisis infiltration in bone marrow, myelofibrosis;
Post-sinusoidal perivenular fibrosis induced by alcohol, veno-occlusive disease by chemotherapy
Post-hepatic obstruction:
Right heart failure;
Constrictive pericarditis;
Budd-Chiari syndrome.
The pathogenesis of portal hypertension were partially elucidated in the last decade. First, the obstruction to portal blood flow increases vascular resistance in the splanchnic vascular bed. This increased resistance results in the formation of portosystemic collaterals. Second, splanchnic vasodilatation occurs with an associated increase in splanchnic inflow. These changes lead to the development of a hyperkinetic systemic circulation.
CLINICAL
When there is obstruction to portal blood flow, blood begins to accumulate in vascular beds that normally drain into the portal vein. Omental congestion contributes to the formation of ascites. Kidnapping blood by the spleen causes splenomegaly and hypersplenism with thrombocytopenia, neutropenia and anemia. Eventually, one side circulatory system (eg varicose veins), is developed to decompress the portal system. The increased flow through the varices and hemorrhoids can lead to rupture, with devastating hemorrhage.
If there is extensive development of varicose veins, a significant amount of portal blood is diverted from the liver, which increasingly will depend more on nutrition for hepatic artery. This deficit limits the regenerative capacity of the liver, which leads to atrophy. It also makes the liver more susceptible to changes in blood pressure. The blood from the intestines passes to the collateral circulation without the necessary clearance by the liver, contributing to hepatic encephalopathy and sepsis.
GASTROINTESTINAL HEMORRHAGE
Gastrointestinal bleeding is a serious complication of portal hypertension. Although many potential causes of bleeding (peptic ulcer, hypertensive gastropathy, varicose veins) coexist in cirrhotic patients, the bleeding comes from the most abundant rupture of varicose veins.
Side esophageal, gastric and haemorrhoid are those who are more prone to profuse bleeding, despite the veins can appear in other locations (surgical scars, ostomies, umbilical vein). The varices are connections between the coronary veins and short gastric and azygos vein. The haemorrhoid veins occur between the portal system and veins haemorrhoid upper and middle.
(P1-P2) = Q x R
The increase in portal resistance can occur anywhere along the venous system, ie in the portal vein or its tributaries before the blood reaches the liver (prehepatic obstruction) in the vascular spaces within the liver (intra-obstruction liver) or after (post-hepatic obstruction). The intra-hepatic obstruction, in turn, is much more complex. Occlusion of small portal branches within the portal triad (pre-sinusoidal obstruction may complicate liver diseases where there is extensive infiltration or fibrosis inflammatory portal and peri-portal. Alternatively, blood flow can be prevented by narrowing of the sinusoids by collagen deposition or occlusion by the same cellular contractile elements (sinusoidal obstruction). Finally, the portal venous flow can be prevented at the terminal hepatic venules, due to occlusion induced by toxins (post-sinusoidal obstruction).
Causes of portal hypertension
Pre-hepatic obstruction
Splenic vein thrombosis
Portal vein thrombosis
Obstruction, intrahepatic;
Pre-sinusoidal schistosomiasis, sarcoidosis, congenital hepatic fibrosis
Sinusoidal fibrosis, alcoholic sickling crisis infiltration in bone marrow, myelofibrosis;
Post-sinusoidal perivenular fibrosis induced by alcohol, veno-occlusive disease by chemotherapy
Post-hepatic obstruction:
Right heart failure;
Constrictive pericarditis;
Budd-Chiari syndrome.
The pathogenesis of portal hypertension were partially elucidated in the last decade. First, the obstruction to portal blood flow increases vascular resistance in the splanchnic vascular bed. This increased resistance results in the formation of portosystemic collaterals. Second, splanchnic vasodilatation occurs with an associated increase in splanchnic inflow. These changes lead to the development of a hyperkinetic systemic circulation.
CLINICAL
When there is obstruction to portal blood flow, blood begins to accumulate in vascular beds that normally drain into the portal vein. Omental congestion contributes to the formation of ascites. Kidnapping blood by the spleen causes splenomegaly and hypersplenism with thrombocytopenia, neutropenia and anemia. Eventually, one side circulatory system (eg varicose veins), is developed to decompress the portal system. The increased flow through the varices and hemorrhoids can lead to rupture, with devastating hemorrhage.
If there is extensive development of varicose veins, a significant amount of portal blood is diverted from the liver, which increasingly will depend more on nutrition for hepatic artery. This deficit limits the regenerative capacity of the liver, which leads to atrophy. It also makes the liver more susceptible to changes in blood pressure. The blood from the intestines passes to the collateral circulation without the necessary clearance by the liver, contributing to hepatic encephalopathy and sepsis.
GASTROINTESTINAL HEMORRHAGE
Gastrointestinal bleeding is a serious complication of portal hypertension. Although many potential causes of bleeding (peptic ulcer, hypertensive gastropathy, varicose veins) coexist in cirrhotic patients, the bleeding comes from the most abundant rupture of varicose veins.
Side esophageal, gastric and haemorrhoid are those who are more prone to profuse bleeding, despite the veins can appear in other locations (surgical scars, ostomies, umbilical vein). The varices are connections between the coronary veins and short gastric and azygos vein. The haemorrhoid veins occur between the portal system and veins haemorrhoid upper and middle.
The natural history of varicose veins suggests that they will develop in approximately 30% of compensated cirrhotic patients and 60% of decompensated. Will appear in 8% of cirrhotic patients each year. Small varicose veins evolve to large. The risk of massive variceal bleeding is 20 to 30% per year. Risk factors are a sign of red on endoscopy, portal pressure gradient greater than 12 mmHg and hepatocytic failure. After the first episode of bleeding, the risk of recurrence is 75 to 80%, especially in the first 6 weeks.
TREATMENT
Medical treatment of portal hypertension is mainly aimed at reducing pressure in the portal system and, consequently, the varicose veins (by vasodilation of the splanchnic venous bed), with reduced risk of fracture (as a preventive measure) and possible reduction or cessation of bleeding asset. In the first case, it is particularly recommended beta-blockers did not cardio-selective (especially propranolol or nadolol), and you can also use isosorbide mononitrate (but with a higher rate of side effects). No active bleeding, the goal is to reduce severe and rapidly portal pressure without causing systemic vasodilatation using somatostatin analogs (octreotide or terlipressin). The treatment and prevention of bleeding varices with other methods than those that act directly on the portal hypertension, are described in a separate article.
Esophageal varices with active bleeding (arrow)
Another treatment option is the shunts ( "short circuit"). This is to divert the flow of one of the major splanchnic veins to reduce portal hypertension, improving liver function and preventing complications. Different forms of shunting of portal to systemic circulation (portosystemic shunt), were described in the treatment, the choice depending on the patent inferior vena cava and the pressure gradient between the portal vein and vena cava, as a minimum gradient of 10 mmHg is necessary to maintain shunt patency in the long term.
In portacaval shunt, the construction portacaval side-to-side is the procedure of choice only if the pressure in the IVC is substantially less than the portal. It has the highest rate of maintenance of the shunt. In mesocava shunt, the shunt in "H" is simple and avoids hilar resection, as the portal vein and IVC adrenal infrastructure liver are not manipulated, allowing liver transplantation in the future. However, it has a high rate of thrombosis (24-53%). In mesoatrial shunt, bypass the liver and the IVC is indicated in patients in whom the IVC is totally or partially occluded, especially if there concomitnte occlusion of hepatic veins.
The TIPS shunt (intrahepatic portosystemic shunt) is a radiological procedure which is performed in a "deviation" between the portal vein and inferior vena cava, through the placement of a prosthesis (stent) that is installed on site by a catheter that was introduced through the jugular vein in the neck to the inferior vena cava. With this derivation, there is reduction in portal hypertension, leading to reduction in ascites, decreased risk of bleeding varices and gastric improvement in hepatorenal and hepatopulmonary syndromes. There is a risk of triggering or worsening hepatic encephalopathy the same if the patient already had, but that can usually be controlled if it is mild. The role of TIPS is usually the "bridge" until the completion of liver transplantation in severe cases (advanced cirrhosis, fulminant hepatic failure), since there is a risk of obstruction of the prosthesis over time (up to 67% on 1 years) and the procedure does not affect the performance of a transplant (as opposed to surgical shunts). TIPS is also effective in controlling bleeding from esophageal varices is difficult to control with medication and / or endoscopic treatment.
Liver transplantation is indicated in place of the shunt for signs of liver failure, especially in cases of fulminant hepatic failure, advanced liver cirrhosis and those who deteriorated rapidly after the shunt was performed.
TREATMENT
Medical treatment of portal hypertension is mainly aimed at reducing pressure in the portal system and, consequently, the varicose veins (by vasodilation of the splanchnic venous bed), with reduced risk of fracture (as a preventive measure) and possible reduction or cessation of bleeding asset. In the first case, it is particularly recommended beta-blockers did not cardio-selective (especially propranolol or nadolol), and you can also use isosorbide mononitrate (but with a higher rate of side effects). No active bleeding, the goal is to reduce severe and rapidly portal pressure without causing systemic vasodilatation using somatostatin analogs (octreotide or terlipressin). The treatment and prevention of bleeding varices with other methods than those that act directly on the portal hypertension, are described in a separate article.
Esophageal varices with active bleeding (arrow)
Another treatment option is the shunts ( "short circuit"). This is to divert the flow of one of the major splanchnic veins to reduce portal hypertension, improving liver function and preventing complications. Different forms of shunting of portal to systemic circulation (portosystemic shunt), were described in the treatment, the choice depending on the patent inferior vena cava and the pressure gradient between the portal vein and vena cava, as a minimum gradient of 10 mmHg is necessary to maintain shunt patency in the long term.
In portacaval shunt, the construction portacaval side-to-side is the procedure of choice only if the pressure in the IVC is substantially less than the portal. It has the highest rate of maintenance of the shunt. In mesocava shunt, the shunt in "H" is simple and avoids hilar resection, as the portal vein and IVC adrenal infrastructure liver are not manipulated, allowing liver transplantation in the future. However, it has a high rate of thrombosis (24-53%). In mesoatrial shunt, bypass the liver and the IVC is indicated in patients in whom the IVC is totally or partially occluded, especially if there concomitnte occlusion of hepatic veins.
The TIPS shunt (intrahepatic portosystemic shunt) is a radiological procedure which is performed in a "deviation" between the portal vein and inferior vena cava, through the placement of a prosthesis (stent) that is installed on site by a catheter that was introduced through the jugular vein in the neck to the inferior vena cava. With this derivation, there is reduction in portal hypertension, leading to reduction in ascites, decreased risk of bleeding varices and gastric improvement in hepatorenal and hepatopulmonary syndromes. There is a risk of triggering or worsening hepatic encephalopathy the same if the patient already had, but that can usually be controlled if it is mild. The role of TIPS is usually the "bridge" until the completion of liver transplantation in severe cases (advanced cirrhosis, fulminant hepatic failure), since there is a risk of obstruction of the prosthesis over time (up to 67% on 1 years) and the procedure does not affect the performance of a transplant (as opposed to surgical shunts). TIPS is also effective in controlling bleeding from esophageal varices is difficult to control with medication and / or endoscopic treatment.
Liver transplantation is indicated in place of the shunt for signs of liver failure, especially in cases of fulminant hepatic failure, advanced liver cirrhosis and those who deteriorated rapidly after the shunt was performed.
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