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 reocurring.
(See also Overview of Blood Vessel Disorders of the Liver Overview of Blood Vessel Disorders of the Liver The liver receives the oxygen and nutrients it needs in blood that comes from two large blood vessels: Portal vein Hepatic artery The portal vein provides about two thirds of the blood. This... read more .)
Because the portal vein is narrowed or blocked, pressure in the portal vein increases. This increased pressure (called portal hypertension Portal Hypertension Portal hypertension is abnormally high blood pressure in the portal vein (the large vein that brings blood from the intestine to the liver) and its branches. Cirrhosis (scarring that distorts... read more ) causes the spleen to enlarge (splenomegaly). It also results in dilated, twisted (varicose) veins in the esophagus (called esophageal varices Gastrointestinal Bleeding Bleeding may occur anywhere along the digestive (gastrointestinal or GI) tract, from the mouth to the anus. Blood may be easily seen by the naked eye (overt), or blood may be present in amounts... read more 
) and often in the stomach (called gastric varices). These veins can bleed profusely.
Fluid accumulation in the abdomen (called ascites Ascites Ascites is the accumulation of protein-containing (ascitic) fluid within the abdomen. Many disorders can cause ascites, but the most common is high blood pressure in the veins that bring blood... read more ) 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 Cirrhosis of the Liver Cirrhosis is the widespread distortion of the liver's internal structure that occurs when a large amount of normal liver tissue is permanently replaced with nonfunctioning scar tissue. The scar... read more 
), 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.
Causes of Portal Vein Thrombosis
About 25% of adults with cirrhosis Cirrhosis of the Liver Cirrhosis is the widespread distortion of the liver's internal structure that occurs when a large amount of normal liver tissue is permanently replaced with nonfunctioning scar tissue. The scar... read more 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 Polycythemia Vera Polycythemia vera is a myeloproliferative neoplasm of the blood-producing cells of the bone marrow that results in overproduction of all types of blood cells. Polycythemia vera is due to mutations... read more ), 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.
Symptoms of Portal Vein Thrombosis
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).
Diagnosis of Portal Vein Thrombosis
Doctors suspect portal vein thrombosis in people who have some combination of the following:
Bleeding from varicose veins in the esophagus or stomach
An enlarged spleen
Conditions that increase the risk of developing portal vein thrombosis (for example, umbilical cord infection in newborns or acute appendicitis in older children)
Blood tests to determine how well the liver is functioning and whether it is damaged (liver tests Liver Blood Tests Liver tests are blood tests that represent a noninvasive way to screen for the presence of liver disease (for example, viral hepatitis in donated blood) and to measure the severity and progress... read more ) are done, but results are often normal.
Doppler ultrasonography Doppler ultrasonography Ultrasonography is a type of medical imaging that uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. During an ultrasound, a device called a... read more 
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 (see Imaging Tests of the Liver and Gallbladder Imaging Tests of the Liver and Gallbladder Imaging tests of the liver, gallbladder, and biliary tract include ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), endoscopic retrograde cholangiopancreatography... read more ).
Treatment of Portal Vein Thrombosis
Drugs (to dissolve or prevent blood clots)
Treatment of cause of blockage and complications
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 reocurring 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 Portal Hypertension Portal hypertension is abnormally high blood pressure in the portal vein (the large vein that brings blood from the intestine to the liver) and its branches. Cirrhosis (scarring that distorts... read more are also treated. Bleeding from varicose veins in the esophagus Control of bleeding Portal hypertension is abnormally high blood pressure in the portal vein (the large vein that brings blood from the intestine to the liver) and its branches. Cirrhosis (scarring that distorts... read more can be stopped using several techniques:
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.
