Investigation of Underlying Causes of Thrombosis

Introduction to Thrombosis Investigation

The American College of Radiology emphasizes that investigating the underlying cause of thrombosis is crucial for treatment decisions, duration of anticoagulation, and risk of recurrence 1

Thrombosis can be classified as provoked by major transient factors, with an annual recurrence risk of less than 1% after 3 months of anticoagulation, and extended therapy is generally not needed 2, 3
Unprovoked thrombosis has an annual recurrence risk of more than 5% and requires consideration for long-term or indefinite anticoagulation 2, 4
Thrombosis provoked by persistent factors, such as active cancer or antiphospholipid syndrome, has the highest recurrence risk and typically requires indefinite anticoagulation 2, 3

The initial assessment for all patients with venous thromboembolism (VTE) should include confirmation of therapeutic anticoagulation status and evaluation of compliance with anticoagulation therapy 1
Patients with acute arterial thrombosis should be evaluated for hypercoagulability, including prothrombin time, partial thromboplastin time, platelet count, and factor V Leiden 5, 6

The American College of Radiology recommends that patients with septic emboli be managed differently than those with VTE, and guidelines for VTE should not be extrapolated to septic thrombosis 5, 6
Hormone-associated VTE in women has a lower recurrence risk if hormones are discontinued, but this should be considered in the context of overall management 4
Cancer-associated thrombosis requires different anticoagulation strategies, typically low-molecular-weight heparin (LMWH) over warfarin, and has higher bleeding risks requiring individualized assessment 8

Bleeding risk should be assessed in all patients, particularly those with cancer, and should include evaluation of platelet count, renal function, liver function, and potential bleeding sources before initiating anticoagulation 8

The clinical algorithm for investigation of thrombosis should include immediate assessment of anticoagulation status, categorization of thrombosis as provoked or unprovoked, and screening for thrombophilia in high-risk patients 1, 2, 3, 5, 6
Anticoagulation duration should be adjusted based on findings, with 3 months of anticoagulation for major transient factors and indefinite anticoagulation for unprovoked or persistent factors 2, 4