La phlebitis is a cardiovascular disorder that corresponds to the formation of a blood clot in a vein. This clot completely or partially blocks blood flow in the vein, like a plug.

Depending on the type of vein affected (deep or superficial), phlebitis is more or less serious. So, if the clot forms in a deep vein, large caliber, treatment must be given in all urgency.

In the vast majority of cases, phlebitis forms in a vein in the legs, but it can appear in any vein (arms, abdomen, etc.).

Phlebitis often occurs after prolonged immobilization, for example, after surgery or due to a cast.

How to recognize a phlebitis?

It is important to distinguish between the 2 types of phlebitis, with very different consequences and treatments.

Superficial phlebitis

In this case, the blood clot forms in a surface vein. It is the most common form, which mainly affects people with varicose veins. It is accompanied by inflammation of the vein and causes pain and discomfort. Although superficial phlebitis may seem harmless, it should be taken as a red flag. Indeed, it is generally a sign of advanced venous insufficiency which can lead to deep phlebitis.

Deep phlebitis

When the blood clot forms in a deep vein whose blood flow is important, the situation is more dangerous since the clot may detach from the wall of the vein. Carried by the blood flow, it can then pass through the heart, then obstruct the pulmonary artery or one of its branches. This then leads to pulmonary embolism, a potentially fatal accident. Most often, this type of clot forms in a vein in the calf.

See in detail the symptoms of phlebitis 

Who is affected by phlebitis?

Deep phlebitis affects more than 1 in 1 people each year. In Quebec, there are approximately 000 cases per year⁶. Fortunately, effective prevention strategies can reduce the frequency of pulmonary embolism and death associated with deep phlebitis.

People at risk

• People who suffer from venous insufficiency or have varicose veins;
• People who have suffered from phlebitis in the past, or whose family member has suffered from phlebitis or pulmonary embolism. After a first phlebitis, the risk of recurrence is multiplied by 2,5;
• People who have major surgery and therefore need to be bedridden for several days (for example, hip surgery) and those who have to wear a cast;
• People hospitalized for a heart attack, heart failure or respiratory failure;
• People who have a pacemaker (pacemakers) and those who have had a catheter placed in a vein to treat another disease. The risk is then greater that a phlebitis appears in an arm;
• People with cancer (some types of cancer cause blood to clot, especially in the chest, abdomen and pelvis). Thus, it is estimated that cancer increases the risk of phlebitis by 4 to 6. In addition, some drugs used in chemotherapy increase the risk of a clot;
• People with paralysis of the legs or arms;
• People with a blood clotting disease (thrombophilia) or an inflammatory disease (ulcerative colitis, lupus, Behçet’s disease, etc.);
• Pregnant women, especially at the end of pregnancy and just after childbirth, see their risk of phlebitis multiplied by 5 to 10;
• People suffering from obesity;
• The risk of phlebitis increases very sharply with age. It is multiplied by 30, from 30 years to 80 years.

Risk factors

• Stay in a position immobile for several hours: working while standing for a long time, making long journeys by car or plane, etc. Trips longer than 12 hours in particular increase the risk. In the airplane, the slightly lower oxygen pressure and the dryness of the air appear to increase the risk further. We even talk about ” economy class syndrome “. However, the risk remains minimal: 1 in 1 million2.
• In women, takinghormone therapy replacement at menopause or oral contraceptives is a risk factor because these medicines increase blood clotting. Oral contraception increases the risk of phlebitis by 2 to 6
• Smoking.

What are the causes of phlebitis?

Although we do not always know the causes, the phlebitis is generally linked to 3 major factors:

• Blood that stagnates in a vein, instead of circulating fluidly (we speak of venous stasis). This situation is typical ofvenous insufficiency and varicose veins, but it can also be due to prolonged immobilization (plaster, bed rest, etc.);
• A lesion in the wall of a vein, caused by the wearing of a catheter, by an injury, etc. ;
• Blood that clots more easily (some cancers and genetic abnormalities, for example, make the blood more viscous). Trauma, surgery, pregnancy can also reduce the blood flow and increase the risk of a clot.

In about half of the people who have it, phlebitis occurs spontaneously without being able to explain it. Nevertheless, risk factors have been discovered. See People at risk and Risk factors.

What possible complications?

The main risk of deep phlebitis is the occurrence of a pulmonary embolism. This accident occurs when the blood clot that has formed in the leg breaks off, “travels” to the lungs and clogs the pulmonary artery or one of its branches. Thus, more than 70% of cases of pulmonary embolism are caused by a blood clot initially formed in a vein in the legs.

In addition, when a deep vein is affected, symptoms of venous insufficiency may occur, for example persistent swelling of the legs (edema), varicose veins and leg ulcers. These symptoms are the result of damage to the valves by the blood clot. Valves are a kind of “valve” which prevents blood from flowing back into the veins and facilitates its circulation to the heart (see the diagram at the beginning of the sheet). In medical terms, it is a post-phlebitic syndrome. Since phlebitis often affects only one leg, this syndrome is usually one-sided.

About the superficial phlebitis, it has long been considered to be harmless. However, several recent studies show that superficial phlebitis often “hides” deep phlebitis that may go unnoticed. In 2010, a French study carried out on nearly 900 patients even showed that 25% of superficial venous thromboses were accompanied by deep phlebitis or pulmonary embolism.⁵.