Portal vein obstruction results from thrombosis (blood clot) or narrowing of the portal vein, which brings blood to the liver from the intestines.
- Most people have no symptoms. Fluid may accumulate in the abdomen, the spleen may enlarge, and severe bleeding may occur in the esophagus.
- Doppler ultrasonography can usually confirm the diagnosis.
- If possible, the cause is treated, and drugs may be used to prevent the clot from enlarging or to dissolve the clot.
Because the portal vein is narrowed or blocked, pressure in the portal vein increases. This increased pressure (called portal hypertension) causes the spleen to enlarge (splenomegaly). It also results in dilated, twisted (varicose) veins in the esophagus (esophageal varices) and often in the stomach (portal hypertensive gastropathy). These can bleed profusely. Fluid accumulation in the abdomen (called ascites) is not common but may develop when the blockage of the portal vein is accompanied by liver congestion or damage or when large amounts of fluids are given intravenously to treat major bleeding from ruptured varices in the esophagus or stomach. Portal vein thrombosis that develops in people with cirrhosis will cause their condition to deteriorate.
About 25% of adults with cirrhosis have portal vein thrombosis, likely from sluggish blood flow. Portal vein thrombosis also can be caused by any condition that makes blood more likely to clot. Common settings differ by age group:
- Newborns: Infection of the umbilical cord stump (at the navel)
- Older children: Appendicitis
- Adults: Excess red blood cells (polycythemia), certain cancers (liver, pancreas, kidney, or adrenal gland), 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). Another vascular complication of portal hypertension is the development of abnormal small veins and capillaries in the stomach (portal hypertensive gastropathy), which may result in gastrointestinal bleeding.
Doctors suspect portal vein thrombosis in people who have some combination of the following:
- Bleeding from esophageal or gastric varices
- An enlarged spleen
- High-risk conditions (for example, children with umbilical cord infection or acute appendicitis)
Blood tests to evaluate the liver often are quite normal.
Doppler ultrasonography usually confirms the diagnosis. It shows that blood flow through the portal vein is reduced or absent. In some, 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 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:
- Usually, rubber bands are inserted through a flexible viewing tube (endoscope), placed 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. (Beta blockers also are used in portal hypertensive gastropathy.)
- Octreotide Some Trade Names
, a drug that also lowers blood flow to the liver and thus decreases blood pressure in the abdomen, may be given intravenously to help stop bleeding.
Occasionally, when these treatments are ineffective, a procedure to create an alternate route for blood flow, bypassing the liver, may be done. Here, the intent is to decompress the portal venous system through creation of a shunt (connection) to the inferior vena cava. The difficulty is creating a shunt when the portal vein is blocked. Also, shunts tend to become blocked.
For some people, liver transplantation is necessary.
Adapted from: Merck & Co., Inc.