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Portal Vein Thrombosis

What is the portal vein?

The portal vein is a very large vein in the abdomen which is responsible for carrying blood from the bowels and other abdominal organs to the liver.



Why is it medically important?


For some unknown reason(s) the portal vein is prone to developing a blood clot. This blood clot usually completely blocks the portal vein. When the vein is blocked, it causes blood to back up in the vein causing high pressures in all the veins below it. The condition is medically known as portal vein thrombosis (PVT). In addition, the organs returning blood to the portal vein, like the spleen, get engorged with blood. In many cases, the body attempts to bypass this blocked vein by developing thin walled veins (collaterals). These collaterals are large and appear like varicosities. The majority of these varicose veins are seen at the lower end of the esophagus (eating tube) but may appear anywhere in the abdomen.

How common is portal vein thrombosis (PVT)?

In the US, PVT is a relatively rare condition with an overall incidence of 5 per 10,000 individuals. The highest incidence of portal vein thrombosis is in Africa and India- probably due to a high incidence of liver infections, parasites and liver cancers. The condition occurs in all ethnic groups and there are no sex differences.

What conditions are associated with PVT?

- Heart failure

- Budd chiari (a childhood condition)

- Constrictive pericarditis (the heart is encased with a stiff covering which

Prevents the heart from beating well)

- Live cirrhosis or scarring

- Cancers of the liver, pancreas, stomach and bile ducts

- Pus in the liver

- Infection of the pancreas (Pancreatitis)

- Infection of the umbilical cord (in babies)

- Pregnancy-pre eclampsia

- Trauma

- Clotting disorders

- Severe dehydration

- Birth control pill

In more than 50% of cases, there is no cause identified. PVT predominantly affects young children, but it can occur in persons of any age. In adults, cancer is a common cause of PVT.

What is life expectancy after PVT?

If there is no liver disease or failure, then the risk of death is low. If bleeding occurs in the presence of liver failure, there is a high chance of dying within a year. More than 30% of individuals with bleeding and liver failure are dead within 2 years.

In children with PVT, the prognosis is much better overall, with a 10-year survival rate greater than 70%, which is attributable to the low incidence of underlying malignancy and cirrhosis.

How does portal vein thrombosis present?

The symptoms of PVT depend on whether the blood clot formation in the portal vein is sudden or a gradual process.

Acute: When the thrombus is acute, the condition is frequently missed. The signs and symptoms are vague. Patients can present emergently with:

- Sudden onset of right upper quadrant pain

- Nausea

- Fever

- Progressive ascites (fluid accumulation in abdomen)

- Intestinal ischemia resulting from propagation of thrombus, or lack of

Intestinal perfusion secondary to acute portal hypertension

- Occasionally, patients may vomit blood (if there is preexisting varices

With liver failure)

Chronic:Individuals with long standing PVT typically always present with vomiting of bright red blood. The amount of bleeding is frightening, even for the physician. Vomiting of blood usually occurs 3-4 years after the initial diagnosis. A few may develop fluid accumulation in the abdomen and others may develop confusion, memory and even coma.

When there is combined liver failure, the condition can deteriorate fast and lead to poor outcomes. When there is a cancer, most individuals do not vomit blood because patients do not survive that long.

Weight loss, loss of appetite, nausea and pain in the abdomen are other common features. Rarely, patients with portal vein obstruction present with a fever of unknown origin.

Can PVT resolve spontaneously?

Spontaneous resolution of the acute thrombus may occur and the symptoms improve. In others, the body may start to develop other vessels (collaterals) to by pass the blockage and the symptoms may not appear. The chronic variety never resolves on its own.

Do all individuals with portal vein thrombosis develop symptoms?

No. In about one third of people with portal vein thrombosis, blockage of the portal vein develops slowly, allowing other blood channels (collateral channels) to become established around the block.

How does one make diagnosis of portal vein thrombosis?

The physical exam and the presentation may give a clue. But if suspected, the diagnosis has to be confirmed by other tests.Diagnosis can be confirmed with:



Ultrasound, MRI or computed tomography (CT) scans may show the blockage. The diagnosis is confirmed by angiography (a dye is injected) and then x rays are obtained. This test is rarely done today because of the availability of CT and MRI

Liver biopsy: To confirm the diagnosis, a liver biopsy is required. This is done by inserting a small needle through the skin and obtaining a small piece of the liver.

Treatment

Acute Bleeding

Many times patients with severe vomiting of blood require urgent treatment and therapy is undertaken to prevent further bleeding.

Sclerotherapy: In the acute setting, treatment is most effective with variceal banding or sclerotherapy, often requiring several sessions to obliterate the bleeding. Both Sclerotherapy and/or banding require the use of a flexible camera placed in the swallowing tube (esophagus). The physician may then either apply a rubber band to ligate or inject the varices with a chemical. This has a success rate of 95% for the acute bleed.

Octreotide: Sometimes a chemical called Octreotide is administered. In the majority of individuals it stops the bleeding but recurrence is high with this approach.

Blood thinners: Sometimes if a recent blood clot has occurred, medications to dissolve the clot are administered. However, this is a very risky procedure because if vomiting of bright red blood is occurring at the same time, the blood thinner will make things worse. The majority of physicians stay away from this therapy because of the tendency to make the bleeding worse.

Surgery: The major aim of surgery is to prevent the thin walled varicosities from rupture and bleeding. There are many surgical techniques to treat these, but since most patients are in poor shape surgery is not a great option. In addition, surgery for PVT requires a multidisciplinary approach with a backup from many specialties. However, the surgery is of high risk and associated with many complications. Surgery is a last resort treatment because of availability of better non surgical methods. Whenever surgery is done in the presence of liver failure, the chances of death and complications are extremely high.

TIPS: Today, newer radiological techniques are available which can make a connection between the liver and the high pressure veins (shunt). This leads to decompression of the varices and a decrease in symptoms. The procedure is done in a radiology suite using x rays. However, TIPS is also associated with some complications which include:

- bleeding inside the abdomen

- failure of the shunt

- dead liver (infarction)

- re blockage of the shunt

The choice of TIPS over shunt surgery depends upon the expertise of the center in these techniques and the availability of a radiologist who is trained in this procedure. TIPS usually occludes over time and requires revision. However, TIPS has the advantage of being less invasive than shunt surgery.

Transplantation

Liver transplant is a great option for those with liver damage. However, the lack of donors and the difficult surgery has limited the option to a few individuals. It is probably the most effective treatment available. Survival is good after a liver transplant but one has to be on life long toxic chemotherapeutic drugs.

What are complications of untreated portal vein thrombosis?

- persistent vomiting of bright red blood

- collection of fluid in the abdomen (ascites)

- dead bowel

- worsening of the liver

- brain confusion, coma

- death

What is the prognosis of individuals with portal vein thrombosis?

Today, we have better treatments and the overall prognosis is good, with 75% of patients alive after 10 years and an overall mortality rate of less than 10%. However, in those individuals who have cancer or liver failure, the prognosis is poor.





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