Get a leg up on deep-vein thrombosis

If you experience leg pain, your first thought may be a strained muscle or an injury. However, if the pain doesn't go away, or if you're unable to identify the cause, it may be a potentially more serious problem: deep-vein thrombosis (DVT), a blood clot that forms in a deep vein, usually in the leg.

Left untreated, a clot may break off, travel to the lungs, and cause a blockage in a lung artery, known as pulmonary embolism (PE). This can be life threatening. "One of the major problems with DVT and PE is lack of awareness of the symptoms associated with these conditions," says Dr. Rachel Rosovsky, a hematologist with Harvard-affiliated Massachusetts General Hospital.

Know the risk factors

Blocked blood flow in a deep leg vein usually causes some swelling in addition to pain. DVT usually occurs in only one leg, but it sometimes develops in both, especially if the clotting is in the pelvic area.

If the clot travels to the lung and becomes a PE, the symptoms may include shortness of breath at rest or during exertion, chest pain, fast or irregular heart rate, and rapid breathing. Severe cases can cause lightheadedness, fainting, and coughing up blood.

People at a high risk for developing DVT or PE are those who've already had an episode. Otherwise, a blood clot in the leg may occur when people are less mobile, such as during a hospitalization; when they've suffered a significant injury; or after they've undergone surgery. Having active cancer, smoking, becoming dehydrated, prolonged sitting (such as long car or plane ride), or being overweight also increases the risk.

"A family history of DVT or PE is an additional risk factor, and therefore it's important to know your family history and share it with your medical provider," says Dr. Rosovsky. People's risk for DVT rises with age, and men have a greater risk than women of developing recurrent blood clots once they've had the first one. It's important to know that anyone can develop DVT or PE," says Dr. Rosovsky, "and up to half the time, a definitive cause is never identified."

Getting diagnosed

If you worry that your leg discomfort might be caused by DVT, call for medical advice. Your doctor will begin with a leg exam, but further testing is often required, such as a D-dimer blood test, a leg ultrasound to look for clots, or both. D-dimers are protein fragments your body produces when it breaks down blood clots. A normal level means DVT is unlikely. However, there are many reasons other than blood clots for an abnormally high D-dimer level.

The diagnosis of PE can be more difficult. "Because there is not one specific sign or symptom solely associated with PE, it can be hard to differentiate from other medical conditions, such as heart attack, heart failure, pneumonia, bronchitis, or a flare-up of asthma or chronic obstructive pulmonary disease," says Dr. Rosovsky.

Doctors often base a PE diagnosis on a predictive scoring system, which considers your symptoms (high heart rate, coughing up blood), risk factors, age, medical history (such as a prior blood clot or recent cancer, immobility, or surgery). If the score indicates a low probability for PE, then your doctor will explore other causes for your symptoms. If the score suggests an intermediate probability, your next step is most likely a D-dimer blood test. If the probability is high, you'll probably be sent directly for imaging, most often a chest CT scan.

Treatment options

Many people with uncomplicated DVT or even PE can be treated as an outpatient with a direct-acting oral anticoagulant (DOAC), such as apixaban (Eliquis), dabigatran (Pradaxa), edoxaban (Savaysa), or rivaroxaban (Xarelto). Anticoagulants prevent additional clot formation. "The sooner a blood clot is diagnosed and people start taking an anticoagulant, the lower their risk of life-threatening complications," says Dr. Rosovsky.

Patients with severe PE may need to be treated with an intravenous anticoagulant (heparin) or injections of a different type of anticoagulant. In special situations, such as when a DOAC is contraindicated, the person may need to take warfarin (Coumadin), an older oral anticoagulant.

"How long people stay on their anticoagulant will depend on what caused the blood clot, whether that cause or other risks are still present, and the bleeding risks associated with each patient," says Dr. Rosovsky. "If the risk was transient, and there are no additional risk factors, then people are often treated for three or maybe up to six months."

Individuals who are at high risk for recurrent blood clots may need to remain on their anticoagulant long-term. These include people who have ongoing risks, such as active cancer, or substantial inherited risk factors. People also may need to take their medication long-term if the cause of the original blood clot can't be identified.

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