Complications of a blood clot (venous thrombosis)

Complications from a blood clot in a deep leg vein can include:

• A blood clot in your lung (pulmonary embolism). This occurs when a piece of the blood clot in the leg vein breaks off and travels to your lungs. Symptoms can include shortness of breath, chest pain, coughing, coughing up blood, and fainting (syncope). Symptoms can be mild if the blood clot is small or can result in death if the blood clot is large. Blood clots that originate in the deep leg veins cause about 90% of pulmonary emboli.¹
• Postthrombotic syndrome. This syndrome is a long-term (chronic) condition that occurs after a blood clot has been treated. Symptoms of this condition include pain, swelling, skin color changes, and sores in the area where the blood clot occurred. Postthrombotic syndrome occurs in about 25 out of 100 people who have a blood clot in the leg and increases the risk for another deep leg vein thrombosis.²

Other rare complications include:

• A blood clot in the veins leading to the kidney (renal vein thrombosis). This can occur if the blood clot in the leg extends into the veins leading to one of the kidneys.
• Amputation of a part or all of the leg. This can occur when blood and oxygen cannot reach an area of the leg or foot because one or more blood clots block blood flow.
• Right-sided heart failure. This occurs when one or more blood clots formed in the legs break loose and travel to the lungs and block blood flow through the lung. Over time, increased blood pressure in the blood vessels leading to the lungs can cause muscle damage to the right side of the heart.
• Paradoxical embolus. This occurs when a blood clot travels through a patent foramen ovale and gets into the arterial system, causing a stroke, heart attack, or other serious complications.

Citations

1. Raskob GE, et al. (2006). Venous thrombosis. In MA Lichtman et al., eds., Williams Hematology, 7th ed., pp. 2055–2065. New York: McGraw-Hill.

2. Kearon C, Hirsh J (2007). Venous thromboembolism. In DC Dale, DD Federman, eds., ACP Medicine, section 1, chap. 18. New York: WebMD.