2. Aetiology of varicose veins

Enlarged tortuous veins arise in 3 situations:

1. Primary (or simple) varicose veins: occur as a result of valvular failure resulting in distended superficial veins in the lower limb. They are the commonest type of varicose vein.
2. Secondary varicose veins: occur when superficial veins carry reversed flow as a collateral mechanism compensating for obstructed neighbouring deep vein. The enforced reverse flow causes enlargement and tortuosity in previously normal veins.
3. Arteriovenous fistula: increased high pressure flow causes engorgement and tortuosity of superficial veins in the vicinity of an arteriovenous fistula.