Definition

Deep vein thrombosis (DVT) is a condition in which a blood clot (thrombus) forms in one or more deep veins of the body. These blood clots typically form in the thigh, pelvis, or lower leg but can also occur in other body parts. Deep vein thrombosis can cause pain or swelling in the legs but can also occur without any symptoms.

Deep vein thrombosis is typically caused by medical conditions that interfere with blood clotting. Blood clots in the legs can also form if you are immobile for an extended time, such as following surgery or an accident, traveling long distances, or lying in bed for an extended time. This condition can be hazardous because the blood clot inside your veins can break free, travel through the bloodstream, and become lodged in your lungs, blocking blood flow to the lungs (pulmonary embolism).

Blood clots can form in veins near the skin's surface in addition to deep veins. This type of blood clot usually does not travel to the lungs unless it first enters the deep veins.

Causes

Deep vein thrombosis is caused by a blood clot in the vein. The blood clot will impede the flow of blood in the body. Blood clots can be caused by a number of things, including :

1. Injury

Damage to the blood vessel wall can narrow or block blood flow and a blood clot may form.

2. Surgery

Blood vessels can be injured during surgery, and this can lead to the formation of a blood clot. Lying in bed with little or no movement after surgery increases the risk of blood clot formation.

3. Decreased mobility

Sitting for too long can accumulate blood in your legs, particularly the lower part. If you cannot move for an extended time, the blood flow to your legs may slow, forming blood clots.

4. Certain medications

Some medications can increase the chances of your blood clotting and forming a blood clot.

Risk Factors

Many factors can increase your risk of developing deep vein thrombosis. The more risk factors you have, the higher your chances of developing deep vein thrombosis. Risk factors for deep vein thrombosis include:

• Age over 60 years 
• Prolonged sitting, such as when driving or sitting in an airplane, causes a decrease in muscle contraction, which reduces blood circulation in the legs
• Lying in bed for a long time, such as during prolonged hospitalization or paralysis
• Injury or surgery on the blood vessels
• Pregnancy can increase pressure on the blood vessels in the pelvis and legs; the risk of blood clots during pregnancy can last for up to six weeks after delivery
• Birth control pills (contraceptives) or hormone replacement therapy
• Being overweight or obese will increase the pressure in the veins in your pelvis and legs
• Smoking can affect the blood clotting process
• Certain types of cancer can increase substances in the blood that cause blood to clot easily
• Heart failure will increase the risk of deep vein thrombosis and pulmonary embolism
• Inflammatory bowel diseases such as Crohn's disease or ulcerative colitis
• Personal or family history of deep vein thrombosis or pulmonary embolism
• Genetic factors that run in families or genetic disorders that make blood clot more easily
• No known risk factors, sometimes blood clots in the veins can occur without any obvious risk factors

Symptoms

Symptoms of deep vein thrombosis are only experienced by roughly half of those with the condition. Common deep vein thrombosis symptoms include:

• Swelling that generally occurs on one side of the foot, ankle, or leg
• Cramping in the affected leg that usually starts in the calf
• Unexplained severe pain in the foot and ankle
• Areas of skin that feel warmer than the surrounding skin
• The skin in the affected area becomes pale, reddish, or blueish, depending on skin tone

Deep vein thrombosis, or blood clots in the upper limbs, such as the arms, may not cause symptoms. If symptoms do occur, they usually include:

• Neck pain
• Pain in the shoulder
• Swelling in the arm or hand
• Blue or darker skin color
• Pain that moves from the upper arm to the lower arm
• Weakness in the hand

Diagnosis

When diagnosing deep vein thrombosis, your doctor will interview you to learn about your symptoms and any risk factors you may have. The doctor will then perform a physical examination, checking the swollen area of the body for tenderness and skin discoloration.

The doctor may also perform some supporting tests to diagnose and rule out other possible diseases, such as:

1. D-dimer Blood Test

D-dimer is a type of protein produced by blood clots. Almost all people with deep vein thrombosis have elevated D-dimer levels in the blood.

2. Duplex Ultrasound

This test uses sound waves to create images of blood flow through your veins. It is the standard test for detecting deep vein thrombosis. During the examination, the examiner gently moves a device across your skin over the area being examined.

3. Venography

A dye will be injected through a large vein in your leg or ankle. X-rays will then generate images of the blood vessels in the legs to detect blood clots. This examination is quite rare. Other tests, such as ultrasound, are often done first.

4. MRI

This test can diagnose deep vein thrombosis in the abdominal veins.

Management

Deep vein thrombosis management aims to stop the blood clot from getting bigger or breaking off and flowing into the lungs and prevent future deep vein thrombosis. The treatment of deep vein thrombosis may include:

1. Medications

Blood thinners are the most commonly prescribed medications for treating deep vein thrombosis. They reduce your blood's ability to clot. You may need to take them for six months. If your symptoms worsen or the blood clot becomes too large, your doctor may prescribe drugs to destroy it. However, this class of drugs has serious side effects such as sudden bleeding, so it is not routinely given.

2. Inferior Vena Cava Filter

The inferior vena cava is one of the large veins that connect to the heart. If you cannot take blood thinners or do not improve after treatment, your doctor may insert a small cone-shaped filter into this vein. The filter can catch large blood clots before they enter the lungs.

3. Compression Stockings

These special socks are extremely tight at the ankle and looser at the knee. These stockings apply pressure to the veins, preventing blood from pooling.

Complications

Complications of deep vein thrombosis may include:

• Pulmonary embolism occurs when a blood vessel in the lungs is blocked by a blood clot that flows into the lungs from another part of the body, typically from your leg
• Post-phlebitis syndrome is damage to the veins caused by a blood clot, which reduces blood flow in the affected area, causing leg pain and swelling, skin discoloration, and skin sores

Prevention

Here are some things you can do to reduce your risk of deep vein thrombosis:

• If you must sit still for an extended time, exercise your lower leg muscles. Stand up and walk at least every half hour on a long flight, or get out of the car every hour on a long road trip.
• Get out of bed and move around as soon as possible following surgery. The faster you move, the less likely you are to develop deep vein thrombosis
• Take medication regularly or use compression stockings (if prescribed by your doctor)
• Stop smoking
• Lose weight if you are obese

When to see a doctor?

Consult a doctor if you experience symptoms leading to deep vein thrombosis.

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