GPAtlas🧭 When to suspect
Suspect superficial vein thrombosis (SVT) – also called superficial thrombophlebitis – in a patient with a painful, tender, red, warm linear streak tracking along the course of a superficial vein, most often in the leg and frequently within a varicose vein. The affected segment classically feels firm and cord-like to the touch.
The word “superficial” is reassuring but can mislead. SVT shares the risk factors of DVT, a concurrent DVT is found in up to a quarter of presentations, and the thrombus can propagate into the deep system at the saphenofemoral or saphenopopliteal junction, causing DVT or pulmonary embolism. SVT is best regarded as part of the venous thromboembolism (VTE) spectrum, not a trivial skin complaint.
The task in primary care is threefold: confirm it is SVT (and not DVT or cellulitis), risk-stratify by clot length and proximity to the deep junction, and never miss extension into the deep veins. Management is driven almost entirely by these two measurements.
| Extent / location | VTE risk | Primary-care action |
|---|---|---|
| < 5 cm, well away from a junction | Low | Symptomatic management; duplex only if not settling or diagnosis unclear |
| ≥ 5 cm, > 3 cm from SFJ/SPJ | Raised | Duplex, then prophylactic anticoagulation – fondaparinux 2.5 mg for 45 days |
| Within 3 cm of SFJ/SPJ | DVT-equivalent | Treat as a DVT – therapeutic-dose anticoagulation for ≥ 3 months |
| Any SVT with confirmed/suspected DVT | High | Treat as a DVT; urgent assessment |
Raise suspicion particularly where there are varicose veins, recent venous trauma (cannulation, injection, sclerotherapy), immobility or long-haul travel, obesity, pregnancy or the puerperium, oestrogen-containing contraception or HRT, previous VTE, active cancer, or a known thrombophilia. Consider the main differentials: cellulitis (more diffuse erythema, no palpable cord), DVT (whole-limb swelling, deep calf pain), and lymphangitis.
Source: ESVS · British Society for Haematology
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