What is the association between ulcerative colitis and pulmonary embolism?

Association Between Ulcerative Colitis and Pulmonary Embolism

Patients with ulcerative colitis have at least a 2-fold increased risk of venous thromboembolism (VTE), including pulmonary embolism, compared to the general population, with the highest risk occurring during active disease and hospitalization. 1

Magnitude of Risk

The thrombotic risk in UC is substantial and clinically significant:

• UC patients face a 2.0 to 2.85-fold increased risk of VTE compared to healthy controls, with pulmonary embolism being one of the most common manifestations alongside deep vein thrombosis 1
• The risk of thrombosis-related mortality is doubled in UC patients compared to controls 1
• Among hospitalized IBD patients undergoing surgery, VTE occurs in 3.3% of UC patients 1
• VTE-associated mortality is significantly elevated: 37.4 per 1,000 hospitalizations for UC versus 9.9 per 1,000 in non-UC patients (p<0.0001) 1

Pathophysiology and Risk Factors

The mechanism underlying this association involves acquired rather than inherited factors:

• The majority of VTE events occur during active disease phases, as inflammatory activity drives hemostatic alterations that promote thrombosis 1
• Hospitalization independently increases VTE risk 8-fold in UC patients 1
• While inherited thrombophilias (Factor V Leiden, prothrombin mutations) occur at similar rates in UC and general populations, the excess VTE risk stems from acquired inflammatory factors 1
• Most VTE events occur in outpatients who have risk factors such as recent hospitalization, surgery, or active disease 1

Clinical Manifestations

Pulmonary embolism presents alongside other thrombotic complications:

• Deep vein thrombosis and pulmonary embolism are the most common thromboembolic manifestations 1
• Unusual sites include cerebrovascular, portal, mesenteric, and retinal veins 1
• VTE is associated with longer hospitalizations (11.7 vs 6.1 days in non-VTE patients) 1
• Recurrent VTE is increased in UC patients: 33.4% recur within 5 years after unprovoked first VTE versus 21.7% in non-IBD patients (relative risk 2.5, p=0.001) 1

Prevention Strategies

All hospitalized UC patients should receive thromboprophylaxis, particularly those with acute severe disease:

• Prophylaxis with low-molecular-weight heparin (LMWH), unfractionated heparin (UFH), or fondaparinux is recommended for all hospitalized UC patients 1
• Both mechanical thromboprophylaxis and pharmacological prophylaxis should be considered in at-risk patients 1
• Rectal bleeding is NOT a contraindication to VTE prophylaxis in UC patients 1, 2
• Extended thromboprophylaxis following hospital discharge should be considered, especially post-surgery 2

Critical Safety Data

A common pitfall is withholding anticoagulation due to bleeding concerns:

• In a meta-analysis of 8 RCTs evaluating heparin in UC (268 patients), only 6 patients had increased rectal bleeding, with only 3 requiring study withdrawal and 1 requiring urgent surgery 1, 2
• Major gastrointestinal bleeding with anticoagulant therapy is rare 1, 2
• The British Society of Gastroenterology (2025) explicitly states that patients with acute severe UC should receive prophylactic LMWH despite bleeding risk 1

Treatment of Established PE

When pulmonary embolism occurs in UC patients:

• Treatment should follow standard antithrombotic therapy guidelines and is independent of the UC diagnosis 1
• Anticoagulation should continue for at least 3 months using LMWH, UFH, or fondaparinux initially, followed by vitamin K antagonists 1
• Long-term anticoagulation should be considered for patients with a second episode of unprovoked VTE 1
• Novel oral anticoagulants (DOACs) have been successfully used in case reports, though guideline evidence primarily supports traditional agents 3, 4

Clinical Implications

The threshold for investigating VTE should be lower in UC patients, especially those with active disease 1

• Diagnosis follows standard protocols: ultrasound for DVT, ventilation-perfusion scan or CT pulmonary angiography for PE 1
• VTE often presents with non-specific symptoms and should be considered in all UC patients with compatible clinical features 1
• Patient education should address modifiable risk factors including oral contraceptive use and long-distance travel 1

Real-World Implementation Gap

Despite clear guidelines, a critical practice gap exists:

• In one retrospective study of 336 hospitalized severe UC patients, only 7% received adequate pharmacological prophylaxis for >80% of their hospitalization 5
• Factors associated with failure to prescribe prophylaxis included hematochezia, elevated platelets, younger male patients, and admission on biologics 5