Understanding the cause of varicose veins starts with understanding how
our blood circulation works. The heart is a strong muscle that pumps fresh
oxygenated blood to all parts of the body. Once this blood reaches its
destination, it drops off its oxygen to the tissues and the veins are responsible
for getting the blood back to the heart for another cycle.
Because the veins don't have a heart muscle to move the blood quickly, the
veins rely on hundreds of one way valves. These valves open to allow blood
to move back towards the heart, then the valves close when gravity tries to
pull the blood back down to the feet. Most varicose and spider veins occur
in the legs, because that is where gravity is putting the most pressure on
the one way valves.
It is when these one way valves get damaged is when you start to see pooling
of blood near the skin resulting in varicose or spider veins.
The most common reason for the valves to become damaged is from a genetic
predisposition (i.e. it runs in the family). The other major reason these
valves become damaged is multiple pregnancies. Even though the first pregnancy
can cause unsightly veins, the second, third and fourth pregnancy generally
make the veins much worse.
Other causes of varicose and spider veins are:
Spider veins are smaller. They range from the size of a strand of hair
up to the size of pencil lead. Larger green or blue veins that are not
bulging from the skin are usually called venules or feeder veins. Veins
that bulge out from the skin while standing or after exercise are varicose
veins. Varicose veins can range from the size of an eraser to the size
of your thumb. No matter which size vein you have, be sure a certified
doctor examines your legs with a Doppler (which listens to the veins and
valves) before having any treatment. Sometimes valves beneath the skin
that can't be seen will be detected by the Doppler.