Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Chronic Venous Insufficiency and Post-Thrombotic Syndrome


The Manual's Editorial Staff

Reviewed/Revised Jun 2023 | Modified Dec 2023
Get the full details
Topic Resources

What are chronic venous insufficiency and post-thrombotic syndrome?

Chronic venous insufficiency is damage to your leg veins that keeps your blood from flowing normally.

Phlebitis is inflammation of one of your veins. It's often caused by a blood clot in your vein. Post-thrombotic syndrome is a problem that happens after you've had phlebitis.

  • Chronic venous insufficiency may cause pain or aching, swelling, skin rash, leg sores, and changes in how your leg looks

  • Doctors do an ultrasound to look at blood flow in your leg veins to tell if you have chronic venous insufficiency

  • To treat chronic venous insufficiency, keep your leg raised, wear compression stockings, and carefully treat any skin sores

What causes chronic venous insufficiency?

Blood Vessels

The main cause of chronic venous insufficiency is:

A blood clot in your vein can cause scarring and problems with the valves in the vein. The valves are 2 flaps of tissue that act like one-way gates. They let blood flow only in one direction, toward your heart. If the valves are damaged, blood collects in your legs. Damage to the valves after having a blood clot in a vein can cause leg problems called post-thrombotic syndrome.

One-Way Valves in the Veins

One-way valves consist of two flaps (cusps or leaflets) with edges that meet. These valves help veins return blood to the heart. As blood moves toward the heart, it pushes the flaps open like a pair of one-way swinging doors (shown on the left). If gravity or muscle contractions momentarily pull the blood backward or if blood begins to back up in a vein, the flaps are immediately pushed closed, preventing backward flow (shown on the right).

One-Way Valves in the Veins

You have a higher chance of having chronic venous insufficiency if you:

  • Have a leg injury

  • Are an older person

  • Are very overweight

What are the symptoms of chronic venous insufficiency?

Symptoms may include:

If you have severe venous insufficiency:

  • Your lower leg may get bigger than normal

  • You may get skin ulcers (open sores) that don’t heal well

How can doctors tell if I have chronic venous insufficiency?

Doctors usually can tell if you have chronic venous insufficiency from your symptoms and a physical exam.

Sometimes doctors will do an ultrasound of your legs.

How do doctors treat chronic venous insufficiency?

Treatment includes:

  • Resting your leg and raising it above your heart—you'll do this for a half hour or longer, at least 3 times per day

  • Compressing (squeezing) your leg using elastic bandages, special stockings, or air-filled wraps connected to a machine that squeezes your legs from time to time

  • Taking good care of any skin sores

Your doctor may use bandages that have medicine in them to help the skin sores heal.

How can I prevent chronic venous insufficiency?

Making changes in your life can help, such as:

  • Losing weight

  • Being active each day

  • Eating less salt (sodium)

quiz link

Test your knowledge

Take a Quiz!