In an adult with unilateral lower‑extremity edema, could this be a sign of pulmonary embolism?

Unilateral Lower Extremity Edema as a Sign of Pulmonary Embolism

Yes, unilateral lower extremity edema can be a sign of pulmonary embolism and should raise clinical suspicion, as it indicates deep vein thrombosis (DVT), which is the source of PE in 70% of cases. 1

Understanding the DVT-PE Connection

Unilateral leg swelling is a critical clinical finding that directly connects to PE pathophysiology:

• In 70% of patients with proven PE, DVT can be detected in the lower extremities, though the thrombus may have partially or completely embolized by the time of presentation 1
• Compression ultrasonography demonstrates proximal DVT in 30-50% of patients presenting with acute PE 1
• The majority of symptomatic DVT involves proximal clots, which are complicated by PE in 40-50% of cases, often without clinical manifestations 1

The absence of leg symptoms does NOT exclude PE—many patients with PE have asymptomatic DVT that has already embolized.

Clinical Significance in Risk Stratification

Unilateral leg swelling carries substantial diagnostic weight in validated prediction rules:

• The Wells score assigns 3 points for "clinical signs of DVT" (leg swelling and pain on deep palpation), making it one of the highest-weighted variables in the scoring system 1, 2
• The revised Geneva score includes "unilateral lower-limb pain" and "pain on deep venous palpation with unilateral edema" as separate scored items 1, 2
• Unilateral leg swelling adds 0.80 coefficient points (odds ratio 2.23) in the Pisa prediction model for PE 1

Diagnostic Implications

When unilateral lower extremity edema is present in a patient with suspected PE:

• Finding a proximal DVT by compression ultrasonography is considered sufficient to warrant anticoagulant treatment without further PE testing, as the treatment is identical 1
• Lower extremity venous ultrasound has 96% specificity for DVT and can be used as initial imaging in patients with obvious signs of DVT 2
• The presence of asymmetric leg swelling is not explained by alternative diagnoses like pneumonia and points specifically toward thromboembolic disease 2

Important Clinical Context

Several caveats apply to interpreting leg edema:

• Symptoms suggestive of DVT include unilateral calf, leg, or thigh swelling or pain, with diagnosis generally based on lower-extremity Doppler ultrasound 1
• Upper extremity venous thrombosis (from central lines or catheters) may be associated with PE in up to 40% of cases, though this typically presents with arm rather than leg swelling 1
• The clinical signs and symptoms of acute PE are non-specific—dyspnea, chest pain, or syncope are the typical presenting complaints, not leg symptoms 1

Practical Diagnostic Approach

For an adult presenting with unilateral lower extremity edema and concern for PE:

• Calculate the Wells score or revised Geneva score to determine clinical probability 2
• If DVT signs are prominent, consider starting with lower extremity venous ultrasound, which if positive for proximal DVT, confirms venous thromboembolism and justifies anticoagulation 1, 2
• If ultrasound shows proximal DVT, patients should still undergo risk assessment for PE severity and risk of early death, as the presence and extent of PE affects prognosis and may influence treatment intensity 1
• If clinical probability is high based on leg swelling plus other PE symptoms, proceed directly to CT pulmonary angiography without D-dimer testing 2

The key pitfall is assuming that leg symptoms must be present for PE to occur—in reality, most PE patients do not have clinically apparent DVT at presentation because the thrombus has already embolized 1.