What is the likelihood of a deep vein thrombosis (DVT) in a 58-year-old female (F) with swelling, dull throbbing pain, and warmth in her right leg, who recently started estrogen patches (hormone replacement therapy) and has no other symptoms?

Assessment of DVT Risk in This Patient

This patient requires immediate evaluation with a Wells score calculation followed by D-dimer testing or compression ultrasound based on her pretest probability, as she has concerning symptoms and a significant risk factor (recent estrogen initiation) that substantially increases her DVT risk. 1

Calculate Wells Score First

Based on the Wells clinical prediction rule, assess the following to stratify her pretest probability 1:

• Localized tenderness along deep venous system: Likely present given "dull throbbing pain" = +1 point
• Entire leg swollen: Need to clarify if entire leg or just calf/ankle
• Calf swelling ≥3 cm compared to other leg: Requires measurement 10 cm below tibial tuberosity
• Pitting edema confined to symptomatic leg: Need to assess
• Collateral superficial veins (nonvaricose): Need to examine
• Alternative diagnosis at least as likely: -2 points if present

Critical point: Recent estrogen patch initiation (started Tuesday, symptoms Friday = 3 days) is a major thrombotic risk factor. Oral estrogen increases VTE risk 2-4 fold, especially in the first year of treatment and particularly in the first few months 2, 3. While transdermal estrogen may have lower risk than oral formulations, it still poses thrombotic risk 2.

Diagnostic Algorithm Based on Wells Score

If Wells Score <2 (DVT Unlikely):

• Order high-sensitivity D-dimer immediately 1, 4
• If D-dimer negative: DVT safely excluded, no further testing needed 1, 5
• If D-dimer positive: Proceed to compression ultrasound 1, 4

If Wells Score ≥2 (DVT Likely):

• Proceed directly to compression ultrasound without D-dimer, as D-dimer would not change management 1, 4
• Complete duplex ultrasound (CDUS) from inguinal ligament to ankle is preferred over limited proximal-only protocols 1

Ultrasound Protocol Recommendations

Complete duplex ultrasound is strongly preferred over limited proximal compression ultrasound because 1:

• Compression performed at 2-cm intervals from inguinal ligament to ankle
• Includes evaluation of posterior tibial and peroneal veins in calf
• Avoids need for repeat scan in 5-7 days (required with limited protocols)
• Single complete study is the safest strategy 1

If only proximal CUS available and negative, she requires either 1, 4:

• Repeat proximal CUS in 1 week, OR
• High-sensitivity D-dimer testing (if positive, repeat CUS in 1 week)

Special Considerations for This Patient

Estrogen-Related Thrombosis Risk

• VTE risk is highest in first few months of estrogen use 2, 3
• This patient is in the highest-risk window (only 3 days of use)
• Timing of symptom onset (3 days after patch initiation) is highly suspicious 2, 3
• If DVT confirmed, estrogen patches must be discontinued immediately 2, 3

Red Flags Requiring Urgent Evaluation

The absence of shortness of breath and chest pain is reassuring but does not exclude DVT 5. However, these symptoms could develop if proximal propagation or embolization occurs 6.

Common Pitfalls to Avoid

• Do not skip pretest probability assessment: Wells score guides appropriate test selection and prevents unnecessary imaging 1
• Do not rely on clinical examination alone: Symptoms and signs of DVT (pain, swelling, warmth) are nonspecific with sensitivity of only 90% for proximal CUS 7
• Do not order D-dimer in high pretest probability patients: It will not change management and delays definitive imaging 1, 5
• Do not accept limited proximal-only ultrasound without follow-up plan: Requires repeat imaging in 1 week to safely exclude calf DVT propagation 1
• Do not forget to evaluate iliac veins if extensive leg swelling with negative standard ultrasound: May indicate isolated iliac DVT 1

Immediate Next Steps

1. Calculate formal Wells score with physical examination findings 1
2. Order appropriate test based on Wells score (D-dimer if <2, ultrasound if ≥2) 1, 4
3. Ensure complete duplex ultrasound is performed if imaging indicated 1
4. If DVT confirmed: Initiate anticoagulation immediately and discontinue estrogen patches 5, 2
5. If DVT excluded: Consider alternative diagnoses (cellulitis, musculoskeletal injury, superficial thrombophlebitis, lymphedema) 5