Workup for Suspected Deep Vein Thrombosis (DVT) in a Patient with Right Calf Pain
The optimal workup for a patient with right calf pain suspected to be DVT should begin with risk stratification using the Wells score, followed by either D-dimer testing or compression ultrasound depending on pretest probability. 1
Risk Stratification Using Wells Score
First, assess the patient's pretest probability using the Wells score:
| 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
Diagnostic Algorithm Based on Pretest Probability
For DVT Unlikely (Wells Score <2):
- Order a highly sensitive D-dimer test
- If D-dimer is negative: No further testing needed (DVT ruled out)
- If D-dimer is positive: Proceed to compression ultrasound (CUS) of proximal veins 1
For DVT Likely (Wells Score ≥2):
- Proceed directly to compression ultrasound (either proximal CUS or whole-leg US) 1, 2
- Proximal CUS examines veins from inguinal ligament to popliteal vein
- Whole-leg US includes calf veins (posterior tibial and peroneal veins)
Interpretation of Ultrasound Results
If Proximal CUS is Positive:
- Treat for DVT rather than performing confirmatory venography 1
If Proximal CUS is Negative:
- For high pretest probability or positive D-dimer: Perform either:
- Repeat proximal CUS in 1 week, OR
- Whole-leg ultrasound 1
- For low pretest probability and negative D-dimer: No further testing needed 1, 3
If Whole-leg US is Negative:
- No further testing is recommended regardless of pretest probability 1
If Isolated Distal DVT is Detected on Whole-leg US:
- Consider serial testing to rule out proximal extension rather than immediate treatment 1
Special Considerations
- In patients with extensive unexplained leg swelling, image iliac veins to exclude isolated iliac DVT 1, 2
- When ultrasound is impractical (e.g., leg casting, excessive subcutaneous tissue) or nondiagnostic, consider CT venography, MR venography, or MR direct thrombus imaging 1
- Measuring calf circumference can be helpful - asymmetric swelling >2cm is associated with DVT in 64% of cases 4
Pitfalls to Avoid
- Relying solely on clinical assessment: Clinical diagnosis of DVT is unreliable in more than 50% of cases 5
- Skipping D-dimer in low-risk patients: A negative D-dimer in low-risk patients has a negative predictive value of 99% 4
- Using D-dimer alone in high-risk patients: D-dimer has limited utility in certain populations (cancer patients, elderly, hospitalized patients) due to high false-positive rates 2
- Failing to consider alternative diagnoses: Other conditions like cellulitis, Baker's cyst, or muscle strain can mimic DVT symptoms
- Not imaging iliac veins in patients with extensive swelling: Isolated iliac DVT can be missed on standard proximal CUS 1
By following this evidence-based approach, you can efficiently and accurately diagnose or exclude DVT in patients presenting with right calf pain, reducing unnecessary testing while ensuring appropriate treatment for those with confirmed thrombosis.