Diagnostic Approach for a 41-Year-Old Patient with Syncope and History of Unilateral Leg Swelling Negative for DVT
In a 41-year-old patient with syncope and history of unilateral leg swelling with negative Doppler for DVT, a comprehensive evaluation for pulmonary embolism (PE) should be performed, as syncope can be a presentation of PE despite negative lower extremity ultrasound. 1
Initial Assessment
- Assess pretest probability for PE using validated clinical prediction rules such as the Wells score or Geneva score, as syncope with prior leg swelling raises concern for possible PE despite negative DVT imaging 2
- Perform D-dimer testing if PE pretest probability is low or moderate; if D-dimer is negative in low-risk patients, PE can be reasonably excluded 1
- Proceed directly to CT pulmonary angiography (CTPA) if PE pretest probability is high, as D-dimer testing alone is not recommended in high-risk patients 2
Further Evaluation of Leg Swelling
- Re-evaluate the prior unilateral leg swelling with whole-leg ultrasound if only proximal compression ultrasound was previously performed, as isolated calf DVT may have been missed 3
- Consider iliac vein imaging (CT venography, MR venography) if there was extensive leg swelling with negative proximal ultrasound, as isolated iliac DVT may be missed on standard ultrasound 3, 1
- Evaluate for non-thrombotic causes of unilateral leg swelling, such as venous compression syndromes, ganglion cysts, or other external compression of veins 4
Syncope Workup
- Perform cardiac evaluation including ECG, echocardiography, and cardiac monitoring to assess for structural heart disease, arrhythmias, or right heart strain that may suggest PE 1
- Consider orthostatic vital signs, as volume depletion can cause both syncope and hemoconcentration leading to increased thrombotic risk 1
- Evaluate for other causes of syncope including neurological, metabolic, and medication-related causes if cardiopulmonary evaluation is negative 1
Laboratory Testing
- Complete blood count to establish baseline values and identify potential contraindications to anticoagulation if PE is diagnosed 5
- Coagulation profile including PT/INR and aPTT to guide potential anticoagulant therapy 5
- Comprehensive metabolic panel to assess kidney and liver function, which will influence anticoagulant selection and dosing if treatment is needed 5
Special Considerations
- If initial testing is negative but clinical suspicion for PE remains high, consider additional imaging such as ventilation-perfusion (V/Q) scan or pulmonary angiography 1
- For patients with recurrent unexplained syncope and negative initial workup, consider extended cardiac monitoring and evaluation for hypercoagulable states 2
- In patients with prior negative DVT studies but persistent symptoms, serial ultrasound testing may be warranted to detect evolving thrombosis 3
Common Pitfalls to Avoid
- Failing to consider PE in a patient with syncope and risk factors for venous thromboembolism, even with negative lower extremity Doppler studies 1
- Relying solely on proximal ultrasound without evaluating iliac veins in patients with extensive leg swelling 3
- Not performing bilateral ultrasound evaluation in patients with unilateral symptoms, as contralateral asymptomatic DVT can be present in 5-15% of cases 6, 7
- Overlooking non-thrombotic causes of unilateral leg swelling that may mimic DVT, such as cellulitis, hematomas, ruptured Baker's cysts, or venous compression syndromes 8