Causes
A variety of things can cause inflammation of a superficial vein. One
common cause is due to trauma or injury, for example from intravenous (IV) catheters
or solutions and medications used in hospitals that pierce the vein wall and
cause irritation. Any blow to a vein (like a blow or injury from a car accident)
will trigger a local inflammatory reaction that leads to pain, discomfort, redness,
and swelling. During this process, there's an increased flow of blood to the
injured area, and a blood clot often forms in the inflamed or injured area of
the vein.
Blood clots in the deep veins of the legs or pelvis are often caused by
inactivity following surgery, stroke, or a major accident that causes people
to be bed-ridden for long periods of time. Blood flow in the veins depends
on contraction of surrounding muscles, so with extended bed rest, the blood
starts to pool and blood clots can easily form.
Sometimes, thrombophlebitis is caused by a bacterial infection in the vein.
The usual culprit is a bacteria called Staphylococcus, commonly found
on the skin. In certain cases, thrombophlebitis develops without an obvious
reason. It may develop in the leg veins of pregnant women, in people with varicose
veins, and in some people with cancer in the abdomen (particularly the pancreas).
Women over the age of 35 years who smoke and take oral contraceptives are at
a higher risk of thrombophlebitis.