Portal vein thrombosis (PVT)
Discuss PVT?
PVT was first described in 1868. PVT consists of two different entities, acute PVT and chronic PVT, which represent successive stages of the same disease.
What are the causes of PVT?
PVT is caused by a combination of local and general risk factors. A local risk factor can be identified in about 30% of patients, and a general risk factor in 70%.
Local risk factors: cancer of any abdominal organ, cirrhosis, inflammatory foci in the abdomen (diverticulitis, appendicitis, cholecystitis, pancreatitis, IBD etc), injury to the portal venous system at surgery
General risk factors: an inherited or acquired prothrombotic condition has been found in many patients with PVT. Thus general thrombophilic factors should be investigated, even when a local factor for portal vein thrombosis is evident. 30%-40% of patients with PVT are affected with chronic, Philadelphia-negative myeloproliferative diseases, usually polycythemia vera, essential thrombocythemia, or unclassified myeloproliferative diseases. Other causes- deficiencies in protein C, in protein S and in antithrombin, gene mutations in factor V Leiden (FVL) and factor II prothrombin. The acquired thrombophilic disorders include malignancy, myeloproliferative disorders, oral contraceptive pills, pregnancy and postpartum, antiphospholipid syndrome and paroxysmal nocturnal haemogobinuria.
Discuss the clinical features of acute PVT?
Diagnosis needs a high index of suspicion and very often radiologist is usually the first physician to suggest the diagnosis on the basis of imaging findings. The patients usually have abdominal pain. Ascites may occur transiently immediately after the thrombotic event. Patients may have abdominal tenderness. Other common complaints of patients with portal vein thrombosis include nausea, vomiting, anorexia, weight loss, diarrhoea and abdominal distension. Liver function is preserved
in patients with acute PVT, however, a transient, moderate increase in serum aminotransferases can be observed in some patients.
The main complication of acute PVT is intestinal ischaemia when thrombosis extends to the mesenteric venules. When the ischaemic is prolonged for several days, intestinal infarction may follow. Clinical features include severe
pain (beyond 5-7 days), bloody diarrhoea, acidosis and ascites. In the absence of treatment, intestinal perforation, peritonitis, shock, and death from multiorgan failure occur.
Discuss the diagnosis of acute PVT?
- CT scan or Doppler sonography
- Investigation of general thrombophilic factors must be extensive because an association of several factors is the rule rather than an exception
Discuss the treatment of acute PVT?
The goal of treatment of acute PVT is to recanalize the obstructed veins, which will prevent intestinal infarction and portal hypertension. Spontaneous repermeation is possible but uncommon, whereas complete or partial repermeation can be achieved with anticoagulant therapy in up to 90% of patients.
- Anticoagulation therapy is recommended for at least 3months in all patients with acute PVT. Anticoagulation therapy should be continued long term in patients with acute PVT and permanent thrombotic risk factors that are not correctable otherwise. Long term anticoagulation should also be considered in patients with acute PVT and thrombus extension distally into the mesenteric vein.
- Correction of the causal factors.
- Emergency laparotomy and resection is needed if intestinal infacrtion occurs.
Discuss chronic PVT?
- The natural history of portal vein thrombosis is not known. Portal hypertension develops when there is no repermeation of the portal vein. The proportion that progress to portal hypertension is not known.
- In patients with chronic PVT, also known as portal cavernoma, the obstructed portal vein is replaced by a network of collateral veins connecting the patent portion of the vein upstream from the thrombus to the patent portion downstream.
- Diagnosis is commonly made after a fortuitous finding of hypersplenism or portal hypertension.
- GI bleeding from varices is better tolerated than in other forms of portal hypertension The occurrence of ascites or encephalopathy in patients with chronic PVT is uncommon.
- A diagnosis of cavernoma is readily made by abdominal imaging with ultrasound, CT or MRI which shows serpiginous structures while the main portal vein and/or its main branches are not visible.
- Consider long-term anticoagulation therapy (to prevent further thrombosis) in patients with chronic PVT, without cirrhosis, and with a permanent risk factor for venous thrombosis, provided there is no major contraindication. In patients with varices, do not initiate anticoagulation until after adequate prophylaxis for variceal bleeding has been instituted.
- Gastroesophageal varices- apply treatment for active variceal haemorrhage and for primary and secondary prophylaxis according to guidelines for patients with cirrhosis.
Discuss PVT and cirrhosis?
PVT is not uncommon in patients with pre-existing cirrhosis. The prevalence of PVT increases with the severity of the cirrhosis. An underlying prothrombotic condition is difficult to detect in cirrhosis because of a nonspecific decrease in the plasma levels of coagulation inhibitors.
Thus, in patients with well-compensated cirrhosis and acute or chronic PVT, there are limited data on the utility of screening for an underlying prothrombotic condition,
and on the benefits of anticoagulation. However, it may be reasonable to consider anticoagulation in the setting of a known prothrombotic condition or in the setting of SMV thrombosis, but only after adequate prophylaxis for gastrointestinal bleeding has been instituted.
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