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Portal Vein Thrombosis
Portal vein thrombosis is blockage or narrowing of the portal vein (the blood vessel that brings blood to the liver from the intestines) by a blood clot.
Most people have no symptoms, but in some people, fluid accumulates in the abdomen, the spleen enlarges, and/or severe bleeding occurs in the esophagus.
Doppler ultrasonography can usually confirm the diagnosis.
The cause is treated if possible, related problems are treated, and drugs may be used to dissolve the clot or to prevent the clot from enlarging or recurring.
Because the portal vein is narrowed or blocked, pressure in the portal vein increases. This increased pressure (called portal hypertension—see Portal Hypertension) causes the spleen to enlarge (splenomegaly). It also results in dilated, twisted (varicose) veins in the esophagus (called esophageal varices) and often in the stomach (called gastric varices). These veins can bleed profusely.
Fluid accumulation in the abdomen (called ascites—see Ascites) is not common. But it may develop when people also have liver congestion (backup of blood in the liver) or liver damage, such as severe scarring of the liver (cirrhosis), or when large amounts of fluids are given intravenously to treat massive bleeding from ruptured varicose veins in the esophagus or stomach. If portal vein thrombosis develops in people with cirrhosis, their condition deteriorates.
About 25% of adults with cirrhosis have portal vein thrombosis, usually because blood flow through the severely scarred liver is slow. When blood flow is slow, blood is more likely to clot. Any condition that makes blood more likely to clot can cause portal vein thrombosis.
Common causes differ by age group:
Newborns: Infection of the umbilical cord stump (at the navel)
Older children: Appendicitis (infection can spread to the portal vein and trigger the formation of blood clots)
Adults: Excess red blood cells (polycythemia), certain cancers (liver, pancreas, kidney, or adrenal gland), cirrhosis, injury, disorders that make blood more likely to clot, surgery, and pregnancy
Often, several conditions work together to cause the blockage. The cause is unknown in about one third of people.
Most people do not have any symptoms.
In some people, problems gradually develop, resulting from portal hypertension. If varicose veins develop in the esophagus or stomach, they may rupture and bleed, sometimes profusely. People then vomit blood. The blood may also pass through the digestive tract, making stools black, tarry, and foul-smelling (called melena).
Doctors suspect portal vein thrombosis in people who have some combination of the following:
Blood tests to determine how well the liver is functioning and whether it is damaged (liver function tests) are done, but results are often normal.
Doppler ultrasonography usually confirms the diagnosis. It shows that blood flow through the portal vein is reduced or absent. In some people, magnetic resonance imaging (MRI) or computed tomography (CT) is necessary.
Angiography is done if a procedure to create an alternate route for blood flow is planned. For angiography, x-rays of the veins are taken after a radiopaque dye (which is visible on x-rays) is injected into the portal vein.
If a blood clot suddenly blocks the vein, a drug that dissolves clots (such as tissue plasminogen activator) is sometimes used. The effectiveness of this treatment (called thrombolysis) is unclear.
If the disorder develops gradually, an anticoagulant, such as heparin, is sometimes used over the long term to help prevent clots from recurring or enlarging. Anticoagulants do not dissolve existing clots.
In newborns and children, the cause (usually an infected umbilical cord or acute appendicitis) is treated.
Problems caused by portal hypertension are also treated. Bleeding from varicose veins in the esophagus can be stopped using several techniques (see Control of bleeding):
Usually, rubber bands are inserted through a flexible viewing tube (endoscope), which is passed through the mouth into the esophagus. The bands are used to tie off the varicose veins.
Antihypertensive drugs, such as beta-blockers and nitrates, reduce pressure in the portal vein and thus prevent bleeding in the esophagus.
Octreotide, a drug that reduces blood flow to the liver and thus decreases blood pressure in the abdomen, may be given intravenously to help stop bleeding.
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