Recommended Anticoagulation Dose for Portal and Splenic Vein Thrombosis
For symptomatic portal vein and splenic vein thrombosis, use therapeutic-dose anticoagulation with low molecular weight heparin (LMWH) at 1 mg/kg subcutaneously twice daily or 1.5 mg/kg once daily, or alternatively use a direct oral anticoagulant (DOAC) at standard VTE treatment doses. 1, 2
Anticoagulation Indication and Timing
Initiate therapeutic anticoagulation immediately upon diagnosis of symptomatic splanchnic vein thrombosis (portal, mesenteric, and/or splenic vein thromboses), as this is a strong recommendation with moderate-certainty evidence. 1
Early anticoagulation prevents thrombus extension in virtually all patients and prevents the catastrophic complication of mesenteric venous infarction. 2
Delayed initiation of anticoagulation is associated with failure to achieve recanalization. 2
For incidentally detected (asymptomatic) splanchnic vein thrombosis, anticoagulation is generally not recommended. 1
Specific Dosing Regimens
LMWH Dosing (Preferred Initial Agent)
Enoxaparin 1 mg/kg subcutaneously twice daily is the most extensively studied regimen for splanchnic vein thrombosis. 3, 4, 5
Alternative dosing: Enoxaparin 1.5 mg/kg subcutaneously once daily has equivalent efficacy and safety. 4
In cirrhotic patients specifically, enoxaparin 200 U/kg/day (approximately 1 mg/kg twice daily) has demonstrated safety and efficacy with complete recanalization in 75% of patients. 3
DOAC Dosing (Alternative)
For patients without cirrhosis or with Child-Pugh A/B cirrhosis, standard VTE treatment doses of DOACs are appropriate:
DOACs are endorsed by the International Society on Thrombosis and Haemostasis for Child-Pugh A and B cirrhosis, representing the most current evidence. 2
Pre-Anticoagulation Assessment
Screen for esophageal varices via endoscopy before initiating anticoagulation, particularly in cirrhotic patients. 2
Ensure varices are adequately treated with beta-blockers or band ligation before starting anticoagulation. 2
If variceal bleeding has occurred, start LMWH only after endoscopic eradication of varices by band ligation. 3
Assess platelet count: Full-dose anticoagulation is appropriate when platelets >50 × 10⁹/L. 2
Do not withhold anticoagulation for moderate thrombocytopenia, as the risk of NOT anticoagulating (intestinal infarction, death) exceeds the bleeding risk. 2
Duration of Therapy
Minimum duration: 3 months of therapeutic anticoagulation for all patients with symptomatic splanchnic vein thrombosis. 1, 6
Treat for at least 6 months in all patients with acute portal vein thrombosis according to European guidelines. 2
Continue beyond 6 months if any of the following are present: 2
- Liver transplant candidates
- Superior mesenteric vein involvement with history of intestinal ischemia
- Underlying permanent prothrombotic conditions
- Incomplete recanalization in transplant candidates
Reassess the need for continued anticoagulation periodically, at least annually. 1, 6
Monitoring Strategy
Assess thrombus extension with CT or MRI at regular intervals during the first 6 months. 2
Monitor for recanalization: Complete recanalization occurs in approximately 33-39% of patients, with partial recanalization in an additional 50%. 3, 7
Poor prognostic indicators for recanalization include delayed anticoagulation initiation, presence of ascites, and occluded splenic vein. 2, 7
Critical Safety Considerations
Active bleeding is the primary contraindication to anticoagulation. 2
Major hemorrhage rates with therapeutic LMWH are low (1.3-2.1%), similar to unfractionated heparin. 4
No significant bleeding complications were observed in cirrhotic patients treated with enoxaparin 200 U/kg/day for at least 6 months. 3
Consider platelet support in the initial 30 days if platelet count is borderline. 2