Causes
A variety of things can cause inflammation of a superficial vein. One common cause is trauma or injury, for example, from IV catheters or certain solutions and medications used in hospitals that pierce the vein wall and cause irritation. Any trauma 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 spillage of blood flow, and a blood clot often forms in the inflamed or injured area of the vein.
Formation of blood clots in the deep veins such as the legs or pelvis are often caused by inactivity following surgery, long air travel, stroke, or a major accident that causes people to be bedridden 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. Thrombophlebitis can also develop in the leg veins of pregnant women, in people with varicose veins, and in some people with cancer of the pancreas). People receiving cancer treatment can also be at risk for developing a DVT. Women over the age of 35 years who smoke and take oral contraceptives are at a higher risk of thrombophlebitis. People who have a pacemaker, a central line (a catheter that is place in a central vein), or are overweight may also be at risk. In certain cases, thrombophlebitis develops without any obvious reason.