How can I differentiate between superficial thrombophlebitis and deep vein thrombosis in a patient presenting with leg pain and swelling?

To differentiate between superficial thrombophlebitis and deep vein thrombosis (DVT) in a patient presenting with leg pain and swelling, consider the following clinical features and diagnostic steps:

• Clinical examination: Superficial thrombophlebitis typically presents with localized pain, redness, and tenderness along a superficial vein, often with a palpable cord. In contrast, DVT usually causes more extensive leg swelling, tenderness along the deep venous system, and may involve the entire leg or calf swelling greater than 3 cm compared to the asymptomatic side.
• Use of the 2-level DVT Wells score: This clinical prediction tool helps estimate the probability of DVT by scoring features such as active cancer, paralysis, recent immobilization, localized tenderness along deep veins, entire leg swelling, calf swelling, pitting oedema confined to the symptomatic leg, collateral superficial veins (non-varicose), and previous DVT. A score of 2 or more indicates DVT is likely, while 1 or less suggests DVT is unlikely.
• Diagnostic testing: For suspected DVT (Wells score ≥2), a proximal leg vein ultrasound scan should be performed promptly to confirm or exclude DVT. If ultrasound is negative but clinical suspicion remains, a D-dimer test can be used to guide further management. Superficial thrombophlebitis does not typically require ultrasound unless DVT is suspected.
• Alternative diagnoses: If DVT is unlikely based on clinical assessment and D-dimer testing, consider superficial thrombophlebitis or other causes of leg pain and swelling.

In summary, differentiation relies on clinical assessment focusing on the location and extent of symptoms, use of the Wells score to estimate DVT probability, and appropriate use of ultrasound and D-dimer testing to confirm or exclude DVT. Superficial thrombophlebitis is more localized and involves superficial veins, whereas DVT involves deep veins and presents with more extensive swelling and tenderness along the deep venous system ¹.