Overall Bottom Line
- PVT can be divided into acute and chronic depending upon the rapidity and cause of the thrombosis.
- PVT is also commonly distinguished according to etiology: tumorous obstruction, that caused by cirrhosis, and hypercoagulable predisposition.
- In patients without cirrhosis, PVT may be the presenting symptom of a myeloproliferative disorder leading to a hypercoagulable state.
- Both local factors and systemic prothrombotic conditions are implicated in the formation of PVT. A local risk factor can be identified in about 30% of patients, and a general risk factor in 70%.
- An abdominal sonogram with Doppler is the imaging study of choice in diagnosing PVT.
Section 1: Background
Definition of disease
- Partial or complete occlusion of the portal vein by a thrombus. Thrombosis of the portal vein is due to a combination of factors, both local and systemic. It may present with a catastrophic ischemia of the bowel or occur in the absence of symptoms in the chronic state with the formation of collateral circulation over time.
Disease classification
- PVT can be classified as acute (thrombus formation without evidence of portal hypertension or collateral circulation) or chronic, also known as portal cavernoma with the formation of a network of collateral circulation.
Incidence/prevalence
- Increasingly recognized as imaging modalities to detect PVT are improving.
- The lifetime risk of developing PVT in the general population is reported to be 1%.
Etiology
- One of the causes of PVT is tumor thrombus. The more common tumors associated with PVT include hepatocellular carcinoma, neuroendocrine tumors, pancreatic cancer and unknown primary.
- Cirrhosis with extended duration of hepatopetal flow may lead to PVT.
- In both the acute and chronic form of PVT (excluding tumors), the cause of PVT is multifactorial with both local and systemic factors contributing to the thrombus formation.
Pathology/pathogenesis
- PVT from tumor is due to a direct extension of the tumor cells into the portal vein. In patients with cirrhosis, thrombus formation is related to increased portal pressure leading to decreased portal blood flow and possibly a decrease in inherent anticoagulants (protein C, protein S, antithrombin III) from decreased hepatic functioning in the setting of cirrhosis.
- In patients without cirrhosis, the most common cause is a systemic hypercoagulable condition in the presence of a prothrombotic disorder. Local factors contributing to the thrombus formation include intra-abdominal infections and inflammatory conditions.
Predictive/risk factors
| Risk factor | Incidence |
|---|---|
| Well compensated cirrhosis | 0.6–16% |
| Decompensated cirrhosis | 35% |
| Non-cirrhotic | 5–10% |
Section 2: Prevention
Clinical Pearls
- In patients with PVT secondary to cirrhosis, anticoagulation is generally not recommended.
- In patients without cirrhosis, long-term anticoagulation is recommended as the most likely cause of thrombus formation in an underlying hypercoagulable condition.
Screening
- Any patient with a previous history of venous thrombus formation should be screened for a prothrombotic condition and anticoagulation should be initiated if the risks of bleeding are low.
Section 3: Diagnosis (Algorithm 28.1)
Clinical Pearls
- History should include symptoms of portal hypertension: abdominal distention, GI bleeding, change in mental status, or in the cases of acute PVT, acute onset of abdominal pain. History should also include any previous episodes of venous thrombus formation. Previous known history of liver disease leading to cirrhosis should also be ascertained.
- Signs of portal hypertension include presence of ascites, varices, encephalopathy and splenomegaly in patients with cirrhosis. In the cases of acute PVT, an acute abdomen with tenderness on examination may be present and liver function is usually preserved.
- Laboratory examinations should include a comprehensive metabolic panel to assess for hepatic functioning (albumin, PT INR, bilirubin), CBC with platelets to reveal elevated white blood cell count possibly indicating an infection as local factors leading to thrombus formation, and evidence of polycythemia or thrombocytosis.
- Color Doppler ultrasonography is the imaging modality of choice. Contrast enhanced CT scan and MRI of the abdomen may also be used for the diagnosis of thrombus in the portal vein.
Differential diagnosis
| Differential diagnosis | Features |
|---|---|
| BCS | Doppler sonography can distinguish location of thrombus |
Typical presentation
- The presentation may differ slightly depending upon the acuteness of the thrombosis.
- In acute PVT (symptoms develop within 60 days of presentation), signs and symptoms of portal hypertension/collateral circulation may be absent. Typically, the patient presents with acute abdominal pain and fever. If the thrombus extends to the mesenteric veins, mesenteric ischemia may ensue leading to life-threatening complications of infarction and sepsis.
- In chronic PVT, the presentation is usually that of complications of portal hypertension including variceal bleeding, ascites and encephalopathy.
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