Are there other vessels besides the pulmonary vessels that need to be evaluated to rule out pulmonary embolism (PE)?

Evaluating Vessels Beyond Pulmonary Arteries for Pulmonary Embolism Diagnosis

When evaluating for pulmonary embolism (PE), lower extremity deep vein thrombosis (DVT) should be assessed in addition to the pulmonary vessels, particularly in patients with contraindications to CT pulmonary angiography or those with high clinical suspicion despite negative pulmonary imaging. 1

Lower Extremity Venous System Evaluation

• Compression ultrasonography of the lower extremities is the primary method for evaluating DVT and should be considered as part of the PE diagnostic workup in specific clinical scenarios 1
• Finding a proximal DVT in a patient with symptoms consistent with PE can be considered diagnostic of venous thromboembolic (VTE) disease and may preclude the need for additional pulmonary imaging 1
• Approximately 30-50% of patients with confirmed PE have detectable DVT on lower extremity ultrasound, making this an important complementary diagnostic approach 1

When to Consider Lower Extremity Ultrasound First

Lower extremity ultrasound may be considered as the initial imaging modality in:

• Patients with obvious signs of DVT for whom venous ultrasound is readily available 1
• Patients with relative contraindications for CT scan (e.g., borderline renal insufficiency, contrast allergy) 1
• Pregnant patients to reduce radiation exposure 1

Role of Lower Extremity Ultrasound After Negative CT Pulmonary Angiography

• For patients with intermediate pretest probability for PE and a negative CT angiogram, consider lower extremity venous ultrasound as an additional test if clinical concern for PE persists 1
• In patients with high pretest probability for PE and a negative CT angiogram, additional testing including lower extremity venous ultrasound should be performed to exclude VTE disease 1

Limitations of Lower Extremity Ultrasound

• A normal ultrasound examination of the leg veins does not rule out PE due to its limited sensitivity (30-50%) in suspected PE patients 1
• Ultrasound cannot completely rule out DVT because it is not sensitive for distal (calf-vein) DVT, though the embolic risk associated with isolated distal DVT is lower unless the thrombus extends proximally 1

CT Venography Considerations

• CT venography can be performed in sequence directly after CT pulmonary angiography to evaluate both the pulmonary arteries and deep veins of the legs, pelvis, and abdomen 1
• This combined approach is rarely used in current practice due to the accuracy of performing separate ultrasound for DVT and the increased burden of contrast and radiation exposure 1
• Unlike venous ultrasound, CT venography allows evaluation of the abdominal and pelvic venous systems, which may be relevant in some cases 1

Diagnostic Strategy Recommendations

• In patients with low clinical probability of PE, a D-dimer test should be the initial approach, with imaging reserved for those with positive results 1
• For patients with high clinical probability of PE, proceed directly to imaging without D-dimer testing 1
• When venous ultrasound is positive in a patient with symptoms consistent with PE, this confirms VTE disease and anticoagulation should be initiated 1

Clinical Relevance of DVT in PE Patients

• Interestingly, patients with high and intermediate risk PE may present with lower incidence of DVT compared to those with low risk PE 2
• In PE patients with comorbid DVT, asymptomatic DVT has been identified as an independent risk factor for high and intermediate risk of PE 2

By incorporating evaluation of the lower extremity venous system alongside pulmonary vessel assessment, clinicians can improve diagnostic accuracy and reduce the need for more invasive or radiation-exposing tests in specific patient populations.