Portal vein thrombosis: causes, symptoms, diagnosis and treatment

The portal vein carries blood from the intestines, spleen and pancreas to the liver. A clot (thrombus) in this vein can partly or completely block that flow. The British Society of Gastroenterology (BSG) revision aid describes PVT as having considerable heterogeneity in its presentation and course, and recommends separating acute from chronic PVT, with or without cirrhosis.

Because the liver also receives blood from the hepatic artery, the liver can often compensate. The BSG notes that, because of a compensatory increase in hepatic arterial blood flow, liver function is usually unaltered even in extensive acute PVT. The problems come from raised pressure upstream (portal hypertension) and, if the clot extends into the mesenteric veins, from reduced blood drainage of the bowel.

The BSG says acute PVT is associated with local conditions such as pancreatitis and/or systemic prothrombotic conditions, for example myeloproliferative neoplasm, antiphospholipid syndrome, paroxysmal nocturnal haemoglobinuria and, occasionally, inheritable thrombophilia. Chronic PVT generally occurs in the setting of cirrhosis, where slow flow is a risk factor, and the BSG estimates an annual incidence of 10 to 15% in that setting. Unrecognised acute PVT can lead to chronic PVT.

The NHS lists a blood clot in the blood vessel that brings blood to the liver among the complications of cirrhosis. The BSG also says all patients with chronic PVT must be assessed for hepatocellular carcinoma. In children, outside cirrhosis, chronic PVT is described as an important cause of portal hypertension in parts of the developing world, sometimes after umbilical sepsis or intra-abdominal infection.

Many people have no symptoms of their own. The BSG says patients with acute PVT may present with symptoms of the precipitating condition, with PVT found incidentally on ultrasound, or with recurrent or severe abdominal pain suggesting venous ischaemia of the gut. Chronic PVT commonly presents without symptoms, or as new-onset or worsening decompensation: ascites, variceal bleeding or hepatic encephalopathy, and cholangitis if there is biliopathy.

The NHS cirrhosis page gives the practical red flags for people with liver disease: call 999 or go to A&E if you are vomiting blood, your poo is very dark or black, or you suddenly become confused or have slurred speech, and get urgent advice for yellow skin or eyes, breathing difficulty or a swollen tummy, legs, ankles or feet. Severe abdominal pain should always be assessed urgently.

The BSG says Doppler ultrasonography of the abdomen is usually the initial test. Cross-sectional imaging such as multiphase contrast-enhanced CT and MR cholangiography helps delineate the extent, acuity and often the local cause, such as hepatocellular carcinoma, pancreatitis, intra-abdominal sepsis, intestinal infarction or portal biliopathy. On Doppler ultrasound acute PVT shows absence of flow, while chronic PVT shows a network of collateral vessels (cavernoma) replacing the portal vein.

Most patients benefit from evaluation for systemic prothrombotic conditions, with the extent individualised and guided by the clinical presentation. In practice this involves a hepatologist or gastroenterologist, and often a haematologist.

According to the BSG, anticoagulation and management of any predisposing factors remain the mainstay of treatment. Spontaneous resolution of acute symptomatic non-cirrhotic PVT is highly unlikely, and immediate anticoagulation is recommended. The usual treatment duration is 6 months if only a transient local cause is found, but it may be extended if there is no identifiable local cause or a persisting systemic cause. For non-cirrhotic chronic PVT, current European recommendations support indefinite anticoagulation.

In people with cirrhosis the decision is more individual: the BSG says anticoagulation can be considered in symptomatic patients with extension of the clot into the superior mesenteric vein or a definite pro-coagulant risk factor, and may be used to support patients on the transplant waiting list. Before anticoagulation in chronic PVT, assessment and prophylaxis for gastro-oesophageal varices is recommended.

Regarding drugs, the BSG says low molecular weight or unfractionated heparin are usually started and overlapped with vitamin K antagonists such as warfarin, and that direct oral anticoagulants should be used only in the context of research, because evidence is lacking. For acute PVT, the BSG reports that prompt anticoagulation can result in recanalisation in 38 to 45% of patients in limited data. Advanced options such as TIPSS (a shunt placed through the liver) and surgery are used in selected cases.

The BSG says spontaneous resolution is common in recent PVT, especially if non-occlusive, and these patients are typically asymptomatic. In cirrhosis, PVT reflects the severity of liver disease and its impact on overall outcome is difficult to assess. People with non-cirrhotic chronic PVT typically survive long-term, with a course characterised by variceal bleeding, portosystemic encephalopathy and portal cavernoma with biliopathy.

On the NHS, PVT is usually managed by a hepatology or gastroenterology service, often with haematology. Private hepatology appointments exist, but anticoagulation, endoscopy for varices and any TIPSS procedure involve specialist units. If you have been told you have PVT, ask your team what the likely cause is, how long treatment is planned and which bleeding or clot symptoms need urgent help.