Etiology of Portal and Hepatic Vein Thrombosis

The cause of portal and hepatic vein thrombosis are multifactorial. With the exception of cancer, myeloproliferative diseases are the most common cause.

Portal Vein Thrombosis

An etiologic factor is present in about 80% of the cases. The two most frequent causes are hepatocellular carcinoma and pancreatic cancer. In the abscence of a neoplastic disease, factors like cirrhosis or a prothrombotic disease must be ruled out.





Chirrosis

The diagnosis of cirrhosis is not always easy, because portal vein thrombosis can be the cause of hepatic dysmorphism, coagulation problems, hypersplenism, and all the other manifestations of portal hypertension. In case of doubt, a liver biopsy should be performed. The best way is to use the transvenous route, this is, with a transjugular liver biopsy. This procedure may help measure the pressure gradient inside the liver parenchyma and thus, distinguish between the different etiologies.

Only 1% of patients with cirrhosis without liver insufficiency have portal vein thrombosis, but 70% of patients with prothrombotic diseases are encountered with the illness. Patients with cirrhosis and some degree of liver insufficiency have a much larger chance of having thrombosis.

Local Causes

The most frequent causes are intraabdominal sepsis, portal vein trauma, splenectomy (for myeloproliferative diseases or hemolytic anemia), pancreatic diseases, and perihilar adenopathies due to tuberculosis.

Intraabdominal sepsis leads to septic pylephlebitis, when the portal vein is in contact with the abscess. It is rare, but can be the cause of extrahepatic PVT in children in up to 50% of the cases. This, usually associated to umbilical vein catheterization or omphalitis. In adults this is seen in about 10-25% of the cases, and usually associated with appendicitis, diverticulitis and cholangitis.

Prothrombotic Diseases

They can be either hereditary diseases or acquired, and are the main cause of PVT in 70% of the cases. Myeloproliferative disease constitute the main cause, but other diseases such as the antiphospholipid syndrome, familiar deficits of coagulation inhibitors (antithrombine III, Protein C), factor V of Leyden, mutations in factor II gene, etc. In every case, a multidisciplinary approach must be set in place for the best treatment.

Hepatic Vein Thrombosis

The primary obstruction of the hepatic veins (HV) due to thrombosis correspond to the 75% of all the causes of HV obstruction in Western countries. The majority are associated to prothrombotic states, but other pathologies can be implicated, such as extrinsic compression, endoluminal tumoral invasion and the membranous obstruction of the inferior vena cava. An etiologic factor can be diagnosed in 90% of the cases.

Classic and occult myeloproliferative diseases are the most common cause and current literature shows that the cause of HV thrombosis is a myeloproliferative disease in two thirds of the cases.

















Other causes especially Budd-Chiari syndrome should be looked for in young women with HVT, Behçet’s disease, Nocturnal Paroxistic Hemoglobinuria, coagulation diseases, etc. A diagnosis of two or more of these diseases is seen in 28% of the cases.

An interesting phenomenon is seen in pregnant women or in the obese, where factor V of Leyden is a frequent cause. In the rest of the cases the cause is not found, and hypothetical suggestions of hepatic vein trauma during labor or because of contractions have been made.



The extrinsic compression as the cause of HVT is rare in Western countries. Usually is secondary to a bening, infectious disease, rather to malignancy.

Japan and India have the highest incidence of membranous obstruction of the vein cava. In most cases the obstruction occurs at the level of the hepatic vein ostium, with one free hepatic vein draining the liver. The hypothesis of a membranous transformation of a thrombus is most probable.

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