Extrahepatic Portal Vein Obstruction

Extrahepatic portal vein obstruction is chronic occlusion of the extrahepatic portal vein, with or without extension into the splenic or mesenteric veins, and development of a cavernoma of collateral veins, in the absence of cirrhosis. Liver function remains largely normal.

It is a leading cause of variceal bleeding in children and young adults, especially in developing regions, and accounts for most portal hypertension in children. Onset is often in childhood, with bleeding by the first or second decade.

Causes are in children: umbilical sepsis, umbilical vein catheterisation, dehydration and congenital anomalies. In adults: prothrombotic disorders (JAK2 V617F mutation and other myeloproliferative neoplasms, factor V Leiden, antiphospholipid syndrome, protein C or S deficiency, paroxysmal nocturnal haemoglobinuria), abdominal infection and surgery, pancreatitis, inflammatory bowel disease and malignancy. A cause remains unknown in a share.

Pathophysiology.

Occlusion raises prehepatic portal pressure, and collaterals form around the thrombosed vein (cavernous transformation) within weeks. Hepatic arterial flow rises to compensate. Compression of the bile duct by collaterals causes portal biliopathy.

Haematemesis or melaena from oesophageal, gastric or ectopic varices, splenomegaly, hypersplenism with low blood counts, growth failure in children, and abdominal discomfort. Ascites is uncommon and usually transient after bleeding. Portal biliopathy may cause jaundice, cholangitis or biliary stones.

Red flags.

• Acute variceal bleeding.
• Acute abdominal pain with vein extension (mesenteric ischaemia).
• Jaundice with fever (cholangitis).

Doppler ultrasound shows absent portal flow and a cavernoma. CT or MR angiography maps the occlusion, collaterals and spleen size. Endoscopy shows oesophageal, gastric and ectopic varices and portal hypertensive gastropathy. Liver tests and synthetic function are usually normal; test blood counts and clotting. Screen for thrombophilia, JAK2 mutation, antiphospholipid antibodies, paroxysmal nocturnal haemoglobinuria and malignancy. Assess portal biliopathy with magnetic resonance cholangiography.

Differential diagnosis.

• Cirrhosis with portal vein thrombosis.
• Tumour invasion of the portal vein.
• Budd-Chiari syndrome.
• Porto sinusoidal vascular disease.
• Splenic vein thrombosis alone.
• Schistosomiasis.

Acute variceal bleeding:

• Terlipressin: 2 mg IV every 4 hours for the first 24 to 48 hours, then 1 mg every 4 hours; up to 5 days; maximum 12 mg daily initially; monitor ischaemia, sodium and ECG; avoid in ischaemic heart disease and peripheral vascular disease.
• Ceftriaxone: 1 g IV once daily; up to 7 days; maximum 2 g daily; monitor renal function and rash.

Add endoscopic band ligation, restrictive transfusion (threshold 70 g/L) and airway protection as needed.

Prevention of rebleeding and primary prophylaxis (large varices): band ligation until eradication, with a non-selective beta blocker.

• Propranolol: 20 to 40 mg orally twice daily, titrated to a resting heart rate of 55 to 60/min; long term; maximum 160 mg daily; monitor heart rate, blood pressure and glucose; avoid in asthma and heart block. Children: 0.5 to 1 mg/kg every 8 to 12 hours, maximum 4 mg/kg daily.

Anticoagulation:

• Enoxaparin (recent thrombosis within 6 months): 1 mg/kg subcutaneously every 12 hours; 3 to 6 months, then long term in a persistent thrombophilia; maximum 150 mg for each dose; monitor platelets, bleeding and anti-Xa in renal impairment; use 1 mg/kg once daily when creatinine clearance is under 30 mL/min. Oral anticoagulants can follow in stable patients.

Shunt surgery (mesenterico left portal bypass, or Rex shunt, in children; splenorenal shunt in adults) is used for refractory bleeding or when variceal control fails. Treat hypersplenism by splenic embolisation if severe. Portal biliopathy treatment is symptomatic with endoscopic therapy or biliary decompression.

Monitoring. Endoscopy every 3 to 6 months until varices are eradicated, then yearly; blood counts, growth in children and Doppler yearly.

Referral and escalation. Hepatology (paediatric hepatology in children), haematology for thrombophilia and surgery for shunt options.