Should I order an ultrasound (US) for swollen and tender legs?

Ultrasound for Swollen and Tender Legs

Yes, you should order an ultrasound for legs that are swollen and tender to palpation, as this is the first-line diagnostic test to evaluate for deep vein thrombosis (DVT). 1

Rationale for Ultrasound

Complete duplex ultrasound (CDUS) is the recommended first-line diagnostic test for evaluating patients with suspected DVT for several reasons:

• High sensitivity (95%) and specificity (100%) for proximal DVT 2
• Non-invasive procedure with no radiation exposure
• Widely available and cost-effective
• Can identify alternative diagnoses causing similar symptoms

Diagnostic Approach

Assessment of DVT Risk

First, consider the clinical probability of DVT using the Wells score:

• 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)

Ultrasound Protocol

The Society of Radiologists in Ultrasound recommends:

1. Complete Duplex Ultrasound (CDUS) which includes:

   • 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 1

2. Examination components:

   • Compression ultrasound to assess vein compressibility
   • Color Doppler to evaluate flow patterns
   • Spectral Doppler to assess waveforms 1

Management Based on Ultrasound Results

If DVT is Confirmed:

• For proximal DVT: Initiate anticoagulation therapy 1
• For isolated distal DVT (calf veins): Consider anticoagulation based on risk factors 1

If Ultrasound is Negative but Clinical Suspicion Remains High:

• Consider repeat ultrasound in 5-7 days 1
• Consider imaging of iliac and pelvic veins if whole-leg swelling persists with normal compression ultrasound 1

Special Considerations

Isolated Distal DVT

For isolated distal DVT, factors favoring anticoagulation include:

• Extensive thrombosis (>5 cm in length, multiple veins, >7 mm diameter)
• Proximity to proximal veins
• Absence of reversible provoking factors
• Active cancer
• History of VTE
• Highly symptomatic presentation 1

Iliac Vein Involvement

If there is whole-leg swelling with normal compression ultrasound of the leg veins, consider imaging of iliac and pelvic veins with:

• Pelvic venous ultrasound
• CT venography
• MR venography 1

Pitfalls to Avoid

1. False negatives can occur with:

   • Partial occlusions
   • Extensive collateral circulation 3
   • Recent thrombosis (<24 hours)

2. False positives can occur due to:

   • External compression of veins
   • Excessive tenderness preventing adequate examination 3

3. Incomplete examination:

   • Failure to assess calf veins can miss isolated distal DVT
   • Failure to assess iliac veins can miss isolated iliac DVT 1

Remember that a single, standardized complete duplex ultrasound examination will simplify the workup and follow-up of most patients with suspected DVT 1.