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WHAT-CAUSES-VARICOSE-VEINS (ETIOLOGY)

Causes of Varicose veins:(ETIOLOGY)
When the normal mechanisms of venous blood flow from the legs fail ‘venous insufficiency’ develops, which manifests in many ways. At its most mild, venous insufficiency causes spider veins which are by and large cosmetic problems only, but can be associated with aching. Slightly larger bluey veins can also result which lie slightly deeper and are called reticular veins. More severe failure causes the common varicose veins and, in 1-2% of the population over 65 years, skin changes and ulcers will result. 
All these are due to high pressure developing in thin walled veins which are designed to withstand low pressures only. Venous insufficiency can be caused by:
Deep vein obstruction.
 
Muscle pump failure.
 
Valve failure.
  
Deep vein obstruction can be caused by DVT (Deep Venous Thrombosis) e.g. in economy class syndrome or by tumours in the pelvis compressing the veins. If it persists it causes valve failure too. 
Muscle pump failure occurs in any condition where the calf muscles are very weak. If this persists it also causes valve failure. 
By far the commonest reason for venous insufficiency and varicose veins is valve failure which can result from inherited valve defects (most common); hormones (e.g. in pregnancy); trauma, previous thrombosis or weak calf muscles.
Once one valve is damaged allowing reflux through it this causes the vein below to stretch. This causes the next valve down to be pulled apart and also fail, leading to a domino type effect with more and more valves failing and eventually a varicose vein becomes prominent.
So you can see the most important factor is your genes; did your mother have varicose veins?
When the valves fail blood flows the wrong way through the veins away from the heart. This is called reflux. The detection, localisation and treatment of reflux is crucial to the effective management of all venous insufficiency problems including varicose veins, reticular veins, spider veins and ulceration.