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What are the outcomes of calf deep vein thrombosis?

Q Can asymptomatic DVT be safely left alone until it has progressed beyond the knee? What is the relationship between later varicose veins and 'silent' DVT?

A Varicose veins are mainly caused by a 'primary' constitutional or genetic weakness in the vein wall leading to dilatation and incompetence of the valves, particularly following

episodes of increased venous pressure, such as during pregnancy.

'Secondary' varicose veins may be a feature of the damage following the post-thrombotic syndrome, which occurs in about 9 per cent of DVTs.

Eighty per cent of DVTs have no signs but are clinically significant. Local signs and symptoms will only appear if venous outflow is acutely obstructed.

Some 20 per cent of untreated, 'silent' calf-vein thrombi and 30 per cent of untreated, symptomatic calf-vein thrombi extend into the popliteal vein, with a 50 per cent risk of pulmonary embolism. Extension to the proximal veins is also associated with a 50 per cent rate of recurrence within three months.

So although initial proximal vein thrombosis is more serious than distal vein thrombosis, at that stage both are clinically important because of the potential to grow and embolise.

Post-thrombotic syndrome is a significant cause of morbidity following symptomatic or asymptomatic DVT.

Venous valvular damage sustained during an episode of thrombosis results in local venous hypertension, which renders the perforating veins of the calf incompetent, resulting in local oedema, varicose veins, skin pigmentation, induration, tissue anoxia and leg ulceration.

The prevalence of venous thrombo-embolic disease is high in all patients confined to bed for a week or more before death.

So when in doubt, consider early referral for D-dimer and appropriate imaging.

Dr Frank Rugman is consultant clinical haematologist at Lancashire Teaching Hospitals NHS Trust

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