Deep vein thrombosis (DVT)

DVT occurs when a blood clot (thrombus) usually develops in a deep vein that runs through the muscles of your thigh and calf or in your pelvis or arm. Each year DVT occurs in around 60,000 people in the UK.

Blood clots can occur due to injury to your veins or sluggish blood flow. As a result, blood vessels become partially or fully blocked, which can make your limb swollen and painful. 

DVT can develop due to a range of medical conditions as well as a lack of movement over time. If left untreated, part of the blood clot can break off and enter your bloodstream, potentially leading to a pulmonary embolism which requires urgent treatment.

What are the causes of DVT? 

DVT is caused by anything that stops your blood from flowing or clotting normally. Risk factors include:

• Being inactive for long periods, for example when travelling long distances or due to surgery, illness or injury, as muscle contractions help blood flow 
• Being over the age of 40 (though it can occur at any age)
• Injury to your veins or surgery
• Having a personal or family history of blood clots or DVT 
• Having certain conditions or treatments, such as cancer and chemotherapy or radiotherapy. Heart failure, varicose veins, or inflammatory bowel disease may also increase your risk of blood clots
• Being pregnant or having recently given birth, increasing pressure on veins in the pelvis and legs
• Being overweight or obese, which also increases pressure on your veins
• Smoking
• Taking the contraceptive pill or hormone replacement therapy (HRT)

Sometimes blood clots can occur in deep veins with no clear risk factor. 

How is DVT diagnosed?

Your GP or consultant will discuss your symptoms and medical history with you and may recommend the following deep vein thrombosis tests to establish a diagnosis:

• D-dimer blood test: This is a quick and relatively non-invasive blood test to measure a substance released in the blood when a clot breaks down. A negative result can rule out DVT, while a positive result needs more investigation. 
• Duplex ultrasound: A deep vein thrombosis ultrasound is a common, reliable imaging test used to diagnose DVT. It uses sound waves to create a picture of your veins and assess blood flow. If there’s a clot, blood flow will be disrupted or absent in the affected area. 
• CT angiography (CTA): This combines a CT scan with an injection of contrast dye to create detailed, cross-sectional images of your blood vessels. It’s especially helpful for diagnosing DVT in unusual locations or when ultrasound results are inconclusive.
• Venogram: This is an X-ray using contrast dye injected directly into you vein. While highly accurate, it's a more invasive procedure that’s typically only used when other tests are inconclusive, or when planning specific interventions.

Treatment of DVT

Deep vein thrombosis treatment aims to stop any clot from getting bigger or breaking loose and becoming a pulmonary embolism. It can also reduce the risk of developing further DVT. 

Treatment for a blood clot in your leg or elsewhere may include one or a combination of medication, compression stockings or surgery. Your treatment options will depend on the extent of your condition, whether any blood clots are loose in your bloodstream and your overall health. 

Deep vein thrombosis medication

DVT blood clot treatment typically begins with medication depending on how advanced your condition is. You may be given anticoagulant medicines, which will thin your blood and make it less likely to develop clots. 

You either take them as tablets or receive them via injections. Your consultant will discuss the different DVT medications such as warfarin and heparin, or newer medications with fewer side effects, and recommend the most suitable type for you. 

If these options don't prove effective, or if your condition is more serious, you may be given medications known as clot busters. You receive these through a small tube called a catheter which is inserted directly into the clot. 

If you have a pulmonary embolism, you'll be given anticoagulant medicine injections for up to five days. You'll then need to take anticoagulant tablets for at least three months afterwards.

Compression stockings

Compression stockings are a non-invasive at-home treatment for DVT. They help stop blood from pooling in your legs and reduce swelling. You may be recommended to wear them for a couple of years where possible, though not overnight. 

Deep vein thrombosis procedures

Minimally invasive procedures 

• Catheter-directed thrombolysis: This procedure involves inserting a thin tube (catheter) into a vein and injecting clot-busting medication directly at the clotted area. This approach may be used for specific cases where traditional clot-busting medications aren’t suitable.
• Mechanical thrombectomy: A catheter is inserted to reach the clot, and a device is used to remove it physically. This approach may be considered for large clots or when thrombolysis is not an option.

Deep vein thrombosis surgery

Surgery for a blood clot in your leg is typically a last resort but can still be effective. 

• Surgical thrombectomy: In rare cases, surgery might be necessary to remove a large clot if other methods aren’t suitable. This typically involves making an incision to access the clot and remove it directly.
• Vena cava filter placement: If you’re at high risk of blood clots but can’t take blood thinners, a small filter may be inserted into a large vein (vena cava) in your abdomen to trap blood clots and stop them from travelling to your lungs.

Can I prevent DVT?

There are things you can do to lower your risk of developing DVT symptoms such as: 

• Avoiding sitting or laying still for long periods of time or crossing your legs while sitting
• Maintaining a healthy weight and staying active
• Drinking plenty of fluids to stay hydrated
• Avoiding smoking and alcohol
• Taking medications and wearing compression stockings as advised by your consultant

Your consultant will discuss the most relevant strategies for you, which may also include taking precautions when travelling and going to hospital for treatment.  

DVT complications

If left untreated, potential complications include:

• Pulmonary embolism: A life-threatening condition which occurs when a blood clot that's formed in your leg or elsewhere breaks loose and travels to your lungs. Symptoms include sudden shortness of breath, chest pain and rapid breathing. You should seek immediate medical attention if you experience them. 
• Post-thrombotic syndrome: Damage to your veins from a blood clot can reduce blood flow to the area, causing symptoms such as pain, swelling and skin colour changes. 

If you're recommended to take deep vein thrombosis medication to thin your blood, it's possible to experience excess bleeding as a side effect. Your consultant will assess this risk and advise on how to manage it, which may include having regular blood tests while taking the medication.