Initial Workup for Leg Swelling
The initial workup for a patient presenting with leg swelling should include assessment of pretest probability using the Wells score, followed by D-dimer testing and/or compression ultrasound based on risk stratification. 1
Clinical Assessment
Wells Score Assessment
Calculate the Wells score to determine pretest probability of DVT:
| Factor | Points |
|---|---|
| Active cancer | 1 |
| Paralysis, paresis, or recent immobilization | 1 |
| Bedridden ≥3 days or major surgery within 12 weeks | 1 |
| Localized tenderness along deep veins | 1 |
| Entire leg swollen | 1 |
| Calf swelling ≥3 cm larger than asymptomatic side | 1 |
| Pitting edema confined to symptomatic leg | 1 |
| Collateral superficial veins | 1 |
| Previous DVT | 1 |
| Alternative diagnosis at least as likely | -2 |
- Score ≥2: DVT likely
- Score <2: DVT unlikely
Key Clinical Features to Evaluate
- Unilateral vs. bilateral swelling (bilateral suggests systemic causes)
- Acute vs. chronic onset
- Associated symptoms (pain, redness, warmth)
- Left-sided swelling (85% of DVTs are left-sided due to compression of left iliac vein) 2
- Specific patterns:
- Isolated buttock/groin/flank pain may indicate iliac vein thrombosis 2
- Entire leg swelling suggests proximal venous obstruction
- Calf-predominant swelling may indicate distal DVT
Diagnostic Algorithm
For Low Pretest Probability (Wells score <2):
- Perform highly sensitive D-dimer test
- If negative: No further testing needed, DVT ruled out 2
- If positive: Proceed to compression ultrasound (CUS) of proximal veins
For High Pretest Probability (Wells score ≥2):
- Proceed directly to compression ultrasound (CUS)
- If positive: Treat for DVT
- If negative with high clinical suspicion: Consider additional testing
Additional Testing Based on Initial Results:
For negative proximal CUS with high suspicion:
- Option 1: Repeat proximal CUS in 1 week
- Option 2: Whole-leg ultrasound
- Option 3: Highly sensitive D-dimer test 2
For extensive unexplained swelling with negative ultrasound:
- Image iliac veins to exclude isolated iliac DVT 1
Specific Imaging Recommendations
First-Line Imaging
- Complete duplex ultrasound is the first-line diagnostic study 1
- Should include compression of deep veins from inguinal ligament to ankle
- Assessment of posterior tibial and peroneal veins in calf
- Spectral Doppler waveforms and color Doppler images
Alternative Imaging Options
When ultrasound is impractical or nondiagnostic:
- CT venography
- MR venography
- MR direct thrombus imaging 2
Special Considerations
Pregnancy
For pregnant patients with suspected DVT:
- Assess for specific risk factors (left leg presentation, >2 cm calf difference, first trimester) 2
- Perform compression ultrasound
- Consider serial ultrasound evaluations (days 0,3, and 7) if initial test is negative 2
- Consider MR venography for suspected isolated pelvic DVT 2
Non-Vascular Causes
Consider non-vascular causes when venous pathology is ruled out:
- Lymphedema (primary or secondary)
- Lipedema (often misdiagnosed, affects approximately 20% of cases in specialized clinics) 3
- Cardiac failure
- Hypoproteinemia (liver or renal failure)
- Medication-induced edema 4
Common Pitfalls to Avoid
- Failing to assess pretest probability using the Wells score 1
- Relying solely on symptoms without structured assessment
- Missing isolated iliac DVT by not imaging iliac veins in patients with extensive swelling 1
- Inappropriate use of D-dimer testing (false positives common in elderly, pregnant patients, etc.)
- Unnecessary venography (rarely required with modern diagnostic algorithms) 1
- Prescribing diuretics without determining underlying cause (particularly problematic in older patients) 4
By following this structured approach to the workup of leg swelling, clinicians can efficiently diagnose or exclude DVT while considering other potential causes, leading to appropriate treatment decisions that will improve patient outcomes.