Deep venous thrombosis (DVT) is a blood clot in a deep vein, most often in the leg. In the US ICD-10-CM system, an acute leg DVT is coded under I82.4-, and the familiar I82.40- codes are used when the specific deep vein is not documented. The final character records the side: 1 for right, 2 for left, 3 for both legs, and 9 for unspecified, so I82.409 is an acute DVT of an unspecified deep leg vein on an unspecified side. This guide covers the coding, diagnosis, treatment, and emerging research on DVT.
What Is Deep Venous Thrombosis?
A DVT forms when blood clots inside one of the large veins that run deep within the muscles, rather than in the surface veins you can see under the skin. Most start in the calf and can extend upward into the knee, thigh, and pelvic veins.
The main danger is that part of the clot breaks off and travels to the lungs, causing a pulmonary embolism (PE). DVT and PE are two faces of the same disease, grouped together as venous thromboembolism (VTE). A second long-term problem is post-thrombotic syndrome, in which damaged vein valves cause chronic leg swelling, aching, skin changes, and sometimes ulcers.
The body has its own system for breaking down clots, called fibrinolysis. Our article on how blood clots dissolve explains this process and why anticoagulants work alongside it.
ICD-10 Codes for DVT
Accurate coding depends on three details in the notes: whether the clot is acute or chronic, which vein is involved, and which side. The table below summarizes the common ICD-10-CM codes.
| Code range | Description |
|---|---|
| I82.40- | Acute DVT of unspecified deep veins of the lower extremity |
| I82.41- | Acute DVT of the femoral vein |
| I82.42- | Acute DVT of the iliac vein |
| I82.43- | Acute DVT of the popliteal vein |
| I82.44- | Acute DVT of the tibial vein |
| I82.4Y- | Acute DVT of unspecified deep veins of the proximal lower extremity |
| I82.4Z- | Acute DVT of unspecified deep veins of the distal lower extremity |
| I82.5- | Chronic DVT of the lower extremity |
| Z86.718 | Personal history of other venous thrombosis and embolism |
Pregnancy-related DVT uses codes from the obstetric chapter instead, and a PE is coded separately under I26. In the original WHO ICD-10 used outside the US, leg DVT is usually coded under I80.2. Using the most specific code available supports accurate records and clearer communication between care teams.
Causes and Risk Factors
Most DVTs can be explained by Virchow’s triad, three conditions that favor clotting:
- Venous stasis: slow blood flow from immobility, long flights, bed rest, paralysis, or a leg in plaster.
- Vein wall injury: surgery (especially hip and knee replacement), trauma, or a central venous catheter.
- Hypercoagulability: blood that clots too readily. See our guide to hypercoagulability for inherited and acquired causes.
Other important risk factors include active cancer, pregnancy and the weeks after delivery, estrogen-containing contraceptives or hormone therapy, obesity, older age, a previous clot, and inherited conditions such as factor V Leiden. For an overview of related conditions, see our article on blood clotting disorders.
Symptoms and Diagnosis
Typical symptoms are swelling of one leg, pain or tenderness in the calf or thigh, warmth, and red or discolored skin. Some DVTs cause no symptoms at all and are found only after a PE. Sudden breathlessness, chest pain that worsens on breathing in, or coughing blood suggest a PE and need emergency care.
Doctors usually combine three steps:
- Clinical probability: a scoring tool such as the Wells score estimates how likely a DVT is based on symptoms and risk factors.
- D-dimer blood test: D-dimer is a fragment released when clots break down. A normal result in a low-probability patient makes DVT very unlikely. A raised result is not specific, because surgery, infection, pregnancy, cancer, and older age can all increase it.
- Compression ultrasound: the first-line imaging test. A vein that cannot be squeezed flat by the probe contains a clot.
Contrast venography, once the reference test, is now rarely needed. CT or MR venography can help when pelvic or abdominal veins are involved.
Treatment and Prevention
Anticoagulants, often called blood thinners, are the cornerstone of treatment. They do not dissolve the existing clot directly. Instead, they stop it growing and prevent new clots while the body’s own fibrinolytic system gradually breaks it down.
- Direct oral anticoagulants (DOACs): apixaban, rivaroxaban, edoxaban, and dabigatran are now first-line for most patients. They do not need routine blood monitoring.
- Low molecular weight heparin: injections used in pregnancy, in some cancer patients, and as a lead-in to certain oral drugs.
- Warfarin: still used in some settings, such as antiphospholipid syndrome, with the INR target usually 2.0 to 3.0.
Treatment usually lasts at least three months. A clot provoked by a temporary trigger such as surgery often needs only that initial course, while an unprovoked clot or ongoing risk may justify longer or indefinite therapy. The decision weighs the risk of another clot against the risk of bleeding.
Clot-busting treatment (thrombolysis) or mechanical clot removal is reserved for selected cases, such as extensive iliofemoral DVT threatening the limb. An inferior vena cava filter is considered only when anticoagulation is impossible. Walking as tolerated is encouraged, and compression stockings may ease symptoms.
Prevention matters in hospital: patients are routinely assessed for VTE risk and may receive preventive heparin or mechanical compression. On long journeys, staying hydrated and moving your legs regularly helps.
Emerging Research in DVT
Research is looking at how best to decide treatment length, how to treat clots in patients with cancer, and how inflammation contributes to thrombosis. A newer class of drugs that target clotting factor XI is under investigation, with the aim of preventing clots while causing less bleeding. These remain investigational for DVT treatment, so current care relies on established anticoagulants. For the wider picture, see our blood clotting guide.
When to See a Doctor
Seek same-day medical assessment for new swelling, pain, or redness in one leg, especially after surgery, a long journey, or during pregnancy. Call emergency services for sudden shortness of breath, chest pain, a racing heart, fainting, or coughing blood.
Frequently Asked Questions
What is the ICD-10 code for DVT of the left leg?
If the specific vein is not documented, an acute DVT of the left leg is coded I82.402 in ICD-10-CM. If the notes name the vein, such as the femoral or popliteal vein, a more specific I82.4 code should be used.
How long does a DVT take to go away?
Pain and swelling often improve within days to weeks of starting anticoagulants. The clot itself may take weeks to months to break down, and some scarring of the vein can remain.
Can I fly after a DVT?
Many people can fly once they are established on anticoagulation and their symptoms are settling, but timing should be agreed with your doctor. Moving your legs and staying hydrated during the flight is sensible.
Will I need blood thinners for life?
Not usually. Most people with a clot linked to a temporary cause stop after about three months. Lifelong treatment is considered for unprovoked or recurrent clots, or when a strong risk factor persists.
