Portal Vein Thrombosis

Thrombotic occlusion, partial or complete, of the portal vein or its branches, occurring in cirrhotic and non-cirrhotic liver disease, and as a manifestation of systemic prothrombotic states or local abdominal pathology.

Causes

• Cirrhosis: the commonest setting, from a combination of reduced portal flow velocity (stasis), local endothelial injury, and the complex "rebalanced" haemostatic state of advanced liver disease which despite prolonged INR is not protective against thrombosis.
• Hepatocellular carcinoma with tumour invasion into the portal vein, an important and prognostically significant differential that must be actively excluded (distinguished from bland thrombus by imaging characteristics).
• Local factors: intra-abdominal infection/inflammation (pylephlebitis --- septic portal vein thrombosis from appendicitis, diverticulitis, pancreatitis, cholangitis), abdominal surgery (particularly splenectomy and bariatric surgery), pancreatitis, and malignancy causing local compression or invasion.
• Systemic prothrombotic states: myeloproliferative neoplasms (a JAK2 mutation should always be sought in unexplained portal vein thrombosis, even with a normal blood count, since splanchnic thrombosis can be the presenting feature of an otherwise occult myeloproliferative neoplasm), inherited thrombophilia, paroxysmal nocturnal haemoglobinuria, antiphospholipid syndrome, and pregnancy/oral contraceptive use.
• Idiopathic in a meaningful minority even after thorough workup.

• Acute presentation: abdominal pain, fever (particularly with septic/pylephlebitic thrombosis), and in extensive thrombosis with mesenteric venous extension, features suggesting bowel ischaemia (severe pain disproportionate to examination, bloody diarrhoea, peritonism --- a surgical emergency).
• Chronic/insidious presentation: often asymptomatic or discovered incidentally on imaging, or presenting with complications of portal hypertension that develop as collateral circulation (cavernous transformation) forms over weeks to months.
• Variceal bleeding (oesophageal or, characteristically, ectopic/portal biliopathy-related), splenomegaly, and ascites (less pronounced than in cirrhotic portal hypertension given preserved hepatic synthetic function in non-cirrhotic portal vein thrombosis).
• Portal biliopathy: biliary strictures/dilation from compression by collateral venous channels (cavernoma) in chronic disease, occasionally causing jaundice or cholangitis.
• In cirrhotic patients, may be entirely asymptomatic and found on surveillance imaging, or may present with decompensation (new/worsening ascites, variceal bleeding) attributable to the thrombosis superimposed on the underlying liver disease.

• Doppler ultrasound is the initial investigation of choice, showing absent or reduced portal venous flow, with an echogenic thrombus visible in the vein; also assesses for cavernous transformation in chronic disease.
• Contrast-enhanced CT or MRI confirms the diagnosis, defines the extent (main portal vein, branches, splenic/mesenteric vein extension), and critically distinguishes bland thrombus from tumour thrombus (enhancement pattern, and the presence of a discrete hepatocellular carcinoma lesion) --- essential in any patient with cirrhosis or risk factors for hepatocellular carcinoma.
• Alpha-fetoprotein if hepatocellular carcinoma is a concern.
• Thrombophilia workup in patients without an obvious local precipitant (particularly younger patients or those without cirrhosis): JAK2 V617F mutation (essential, even with a normal blood count), paroxysmal nocturnal haemoglobinuria flow cytometry, antiphospholipid antibodies, and inherited thrombophilia screen (factor V Leiden, prothrombin gene mutation, protein C/S and antithrombin --- recognising these natural anticoagulants may be reduced due to liver synthetic dysfunction rather than true deficiency in cirrhotic patients, complicating interpretation).
• Assess for underlying local intra-abdominal cause: inflammatory markers, blood cultures if septic thrombosis (pylephlebitis) is suspected, and imaging/history for pancreatitis, appendicitis, diverticulitis or recent abdominal surgery.
• Endoscopy to assess for varices in patients with established chronic portal vein thrombosis and portal hypertension.

• Anticoagulation is the mainstay for acute portal vein thrombosis in non-cirrhotic patients, typically with low molecular weight heparin transitioning to a vitamin K antagonist or direct oral anticoagulant, aiming for recanalisation and to prevent extension/mesenteric ischaemia; generally continued for at least 3-6 months, with indefinite anticoagulation considered for those with an identified persistent prothrombotic state (myeloproliferative neoplasm, antiphospholipid syndrome) or extensive/recurrent thrombosis.
• Anticoagulation in cirrhotic patients with portal vein thrombosis is more nuanced given bleeding risk, but is increasingly recommended for acute or progressive thrombosis, particularly in transplant candidates (where thrombosis complicates surgical anastomosis and worsens outcomes) --- decisions should involve hepatology and be individualised balancing variceal bleeding risk against thrombotic progression.
• Anticoagulation is contraindicated or requires extreme caution with active bleeding, and variceal risk should be assessed (and varices banded/treated) before or concurrently with anticoagulation initiation in cirrhotic patients.
• Septic (pylephlebitic) portal vein thrombosis requires treatment of the underlying intra-abdominal source (antibiotics, drainage of any abscess, surgery if indicated) alongside anticoagulation.
• Suspected mesenteric ischaemia from extensive thrombosis is a surgical emergency requiring urgent surgical assessment, resuscitation, and likely laparotomy.
• Management of portal hypertension complications as they arise: variceal band ligation and non-selective beta blockade for bleeding prophylaxis, management of ascites, and surveillance endoscopy.
• Hepatocellular carcinoma with portal vein tumour thrombus is managed per hepatocellular carcinoma staging and treatment protocols (systemic therapy in most cases given advanced stage), distinct entirely from anticoagulation of bland thrombus.
• Long-term monitoring for recanalisation, cavernous transformation, and portal biliopathy with periodic imaging.
• Liver transplant assessment in appropriate cirrhotic candidates, with portal vein thrombosis status factored into surgical planning (may require thrombectomy or alternative venous reconstruction techniques).