Arteries bring oxygen-rich blood from your heart to the rest of your body, whereas your veins are the blood vessels that return oxygen-poor blood back to your heart. You have three kinds of veins. Superficial veins lie close to your skin, and the deep veins lie in groups of muscles. Perforating veins connect the superficial veins to the deep veins with one-way valves. Deep veins lead to the vena cava, your body’s largest vein, which runs directly to your heart. Deep vein thrombosis (DVT) is a blood clot in one of the deep veins. Usually, DVT occurs in your pelvis, thigh, or calf, but it can also occur less commonly in your arm, chest, or other locations.

DVT can cause sudden swelling, pain or a sensation of warmth. DVT can be dangerous because it can cause a complication known as pulmonary embolism. In this condition, a blood clot breaks free from your deep veins, travels through your bloodstream, and lodges in your lungs. This clot can block blood flow in your lungs, which can strain your heart and lungs. A pulmonary embolism is a medical emergency. A large embolism can be fatal in a short time.

It can sometimes be difficult to recognize the symptoms of DVT. However, the condition can be effectively treated once your physician diagnoses it.

About half of all DVT cases do not cause symptoms. The symptoms you feel can depend on the location and size of your blood clot. They include swelling, tenderness, leg pain that may worsen when you walk or stand, a sensation of warmth, and skin that turns blue or red.

When something goes wrong with your body’s blood clotting system, DVT can occur. Once a small clot forms in your vein, it can cause an inflammation that may encourage more blood clots to form.

Often, poor blood flow, or stagnation of blood flow, in your leg veins increases the risk for DVT. This poor flow can occur when you are not able to move for long periods of time. As a result, when your blood pools in your veins, clots are more likely to form. Some specific causes of DVT include:

Although it is true that long airplane flights can increase your risk of DVT, this rarely occurs. Most cases of DVT occur in sick, hospitalized patients.

You have a greater chance of developing DVT if you are obese, have a history of heart attack, stroke or congestive heart failure, are pregnant, nursing or taking birth control pills, or have inflammatory bowel disease.

Most cases of DVT affect the legs, but DVT in the upper body is becoming more commonly recognized. Some factors that increase your chances of developing DVT in the upper body include:

First, your physician asks you questions about your general health, medical history, and symptoms. In addition, your physician conducts a physical exam. Together these are known as a patient history and exam. To confirm a diagnosis of DVT, the physician may order a duplex ultrasound test or another test called a venogram.

our physician or vascular surgeon can usually treat DVT with medications or minimally invasive procedures. Rarely, surgery may be required.

If you have DVT, your physician may inject an anticoagulant drug called heparin. Anticoagulants are also called blood thinners. They don’t literally thin your blood, but they help prevent your blood from clotting too easily. Heparin helps prevent clots from forming and keeps clots you already have from growing larger. However, heparin cannot break up a clot that you already have. Heparin acts rapidly but must be given by vein. Alternatively, your physician may prescribe a medication known as a low molecular weight heparin (LMWH). This has many of the same effects as heparin, but is given through an injection in the abdomen once or twice a day.

Usually, you will receive heparin (or LMWH) for five to seven days. After that, you will take an anticoagulant pill called warfarin (Coumadin), usually for 6 months. It can take a few days for the warfarin to take effect, and during that time period you may be on both heparin (or LMWH) and warfarin. During the time you are receiving medication, your physician will order blood tests to make sure your anticoagulation level is adequate to prevent clots, but not too high to cause excessive bleeding. Anticoagulants can cause bleeding problems if the dosage is too high.

If your physician wants to dissolve the clot, he or she may recommend thrombolysis. In this procedure, your vascular surgeon injects clot-dissolving drugs through a catheter directly into the clot. Thrombolysis has a higher risk for bleeding complications and stroke than anticoagulant therapy. However, thrombolysis can also dissolve very large clots. Your vascular surgeon may prefer to use thrombolysis if you have a high risk for pulmonary embolism or, sometimes, if you have DVT in your arm.

Rarely, physicians recommend surgery to remove a deep vein clot. The procedure is called venous thrombectomy. You may need this surgery if you have a severe form of DVT called phlegmasia cerulea dolens, which does not respond to adequate non-surgical treatment. Phlegmasia cerulea dolens, if not adequately treated, can cause gangrene, which is tissue death and occurs when tissues in your body do not receive enough oxygen and blood. Gangrene is very serious and can lead to amputation.

Physicians know that DVT is more likely if you have surgery. If you are scheduled for surgery, your physician may recommend one or more of the following, to prevent DVT: