A blood clot, also called thrombus, may develop in the calf in superficial veins that are just under the skin or in those deep within the leg. A calf vein is the most common place for a deep vein thrombosis, also known as DVT. The major complication of DVT occurs when the clot breaks off and travels to the lung, causing pulmonary embolus, or PE. According to the American Society of Hematology, each year an estimated 900,000 patients in the United States develop blood clots in deep veins, resulting in 300,000 deaths from pulmonary embolus.
Blood Clots
Clotting is the body’s normal and necessary way to prevent excessive bleeding; blood clots form to seal small cuts or breaks in blood vessel walls. Clots may also develop because of sluggish blood flow in the vessels. A small blood clot usually does not block the vein and allows normal blood flow. However, if a clot prevents the flow of blood or blocks a vein or artery, it can be hazardous. Being hospitalized, confined to bed rest, having major surgery, pregnancy, obesity, suffering a trauma or traveling for several hours increases the risk of deep vein thrombosis and pulmonary embolism.
Superficial Vein Thrombus
With a superficial blood clot, the skin over the affected vein becomes red, swollen, warm, tender and sometimes very painful. The vein may feel like a hard cord along its entire length. Occasionally a black and blue mark, a hard bluish lump or a red streak can be seen under the skin at the vein. Blood clots in superficial veins cannot travel to the lungs. Until recently, association between SVT and DVT had been debated. Researchers have shown, however, that as many as 40 percent of patients with superficial clots have a progression to deep venous thrombosis. A 2009 landmark study conducted at the Medical University of Graz, Austria, corroborated findings from 2005 research at the Department of Emergency Medicine, Padua, Italy, about the risk of subsequent complications in patients with superficial blood clots.
Deep Vein Thrombosis
The CDC reports that DVT is a preventable but often undiagnosed condition because 50 percent of patients have no symptoms. Patients with symptoms report pain, inflammation and swelling. The affected limb is warm to the touch, may have a red, blue or whitish discoloration and may feel “full” or “plugged.” Pain may gradually increase, similarly to that of pulled a muscle that worsens when bending the foot. Over time, as circulation diminishes, the leg becomes cooler than the unaffected limb and has a “pins-and-needles” tingling sensation. According to the National Institutes of Health, most DVTs resolve unaided, but the NIH warns that individuals who have had one DVT are more likely than the average person to have another.
About this Author
Joanna Kaufman, R.N., M.S., is the primary author and editor of the Institute for Family-Centered Care‘s website and monthly e-newsletter. Her first article, a piece about caring for children with catastrophic illness at home, appeared in Caring in 1985.
