Deep vein thrombosis is a blood clot that forms in a deep vein, most often in the legs. A DVT can cause leg swelling, tightness, and discomfort, but some clots are silent. When a clot limits normal blood return from the leg, pressure builds, tissue becomes inflamed, and walking can feel uncomfortable. Recognizing risk factors and early symptoms—then getting timely care—helps protect your mobility and reduce the chance of serious complications.
Causes Of Deep Vein Thrombosis?
Deep vein thrombosis develops when several forces overlap to favor clot formation. Clinicians describe this as Virchow’s triad: slower‑than‑normal blood flow in the veins (stasis), irritation or injury to the vein wall (endothelial injury), and a blood state that is more prone to clotting (hypercoagulability). Most people who develop a DVT have more than one factor at play—for example, a long car ride after recent surgery, or starting estrogen therapy while also having a family tendency to clot.
Sluggish Blood Flow (venous stasis)
When the calf muscles aren’t contracting regularly, venous blood moves more slowly and is more likely to clot. This happens with prolonged sitting or bed rest, long travel by plane or car (typically more than 4–6 hours without movement), leg casts or splints, paralysis, and after a stroke. Heart failure and severe dehydration can also slow venous return. Obesity adds pressure to pelvic and leg veins and is an independent risk factor, especially when combined with immobility.
Vein Injury or Compression
Anything that irritates or compresses a vein can trigger clotting. Common examples include recent surgery (particularly orthopedic hip, knee, or pelvic procedures), fractures and trauma, and childbirth or cesarean delivery. Indwelling devices—such as PICC lines, chemotherapy ports, dialysis catheters, and pacemaker/defibrillator leads—can injure the vessel from the inside and are a leading cause of upper‑extremity DVT. Repetitive overhead arm activity may cause “effort thrombosis” (Paget‑Schrötter syndrome) by narrowing the vein at the thoracic outlet. In the pelvis, an anatomic narrowing called May‑Thurner syndrome—where the right iliac artery compresses the left iliac vein—can predispose to left‑sided leg DVT, especially in young to middle‑aged adults. External compression from pelvic masses, large uterine fibroids, or the uterus in late pregnancy can also impair venous flow. Tight casts or braces that limit ankle movement contribute by reducing the calf‑muscle pump.
A blood state that clots more easily (hypercoagulability)
Some people inherit tendencies that make clotting more likely. The most common inherited risks are factor V Leiden and the prothrombin G20210A mutation; less common but often higher‑risk conditions include deficiencies of protein C, protein S, or antithrombin. These do not guarantee a clot will occur, but they increase the chance—particularly when combined with a strong trigger like surgery or immobilization.
Acquired (non‑inherited) conditions are at least as important. Cancer—especially pancreatic, stomach, lung, brain, and ovarian cancers—and some treatments (for example, cisplatin‑based chemotherapy or thalidomide/lenalidomide combinations) markedly increase clot risk. Antiphospholipid syndrome (an autoimmune condition), myeloproliferative neoplasms such as polycythemia vera (often associated with a JAK2 mutation), nephrotic syndrome, and severe infections including COVID‑19 raise clotting tendency. Pregnancy and the six weeks after delivery are naturally hypercoagulable periods; the risk is higher with cesarean delivery, preeclampsia, or prolonged bed rest. Estrogen‑containing birth control and menopausal hormone therapy increase risk, particularly in smokers or those with inherited thrombophilia; transdermal estrogen may carry lower risk than oral in some patients. Select medications such as tamoxifen/raloxifene (SERMs) and high‑dose testosterone that causes elevated hematocrit can also contribute. Chronic inflammatory diseases (inflammatory bowel disease, lupus, rheumatoid arthritis), chronic kidney disease, and smoking all add to risk, and risk rises with age.
Special situations worth knowing:
- Travel‑related DVT: Sitting still on flights or car rides longer than about 4–6 hours increases risk, and the effect is stronger if you also use estrogen‑containing hormones, have obesity, or a prior clot. Standing up or doing calf raises every hour, staying hydrated, and wearing compression when advised can help.
- Hospitalization and surgery: The highest risk window is during a hospital stay and for up to 90 days afterward, especially after hip/knee replacement, major cancer surgery, or traumatic injury. Preventive strategies (early walking, compression, and when appropriate, preventive blood thinners) are important.
- Pregnancy and postpartum: Clots are more likely in the left leg due to pelvic vein compression and hormonal changes. New one‑sided swelling, pain, or warmth in pregnancy or after delivery should be evaluated promptly. Safe, pregnancy‑appropriate treatments are available.
- Upper‑extremity DVT: Central venous catheters, pacemaker leads, and repetitive overhead activity are common triggers. Symptoms often include arm swelling, heaviness, and visible chest or shoulder veins.
Putting it together: why many clots are “multifactorial”
DVT usually isn’t caused by a single factor. A person might have a mild inherited tendency and then take a long flight, start an estrogen therapy, or undergo surgery—together, these tip the balance toward clotting. That’s why we take a full history, including recent travel, operations, medications and supplements, family clotting history, prior miscarriages (a possible clue to antiphospholipid syndrome), and any devices like PICC lines or pacemakers. We also consider anatomic contributors such as May‑Thurner syndrome in patients with left‑sided, extensive clots.
What you can influence
You cannot change your age or genetics. However, you can lower your risk by moving regularly. Avoid sitting for long periods. Stay hydrated, especially when you travel. Keep a healthy weight. Stop smoking. Talk to your doctor about hormone or testosterone therapy options. Before surgeries or periods of limited mobility, ask about a personalized prevention plan. If you have a history of DVT, let your care team know before future procedures or long trips.
Symptoms To Watch For
The most common signs are one-sided leg swelling, a feeling of tightness or heaviness, and calf or thigh tenderness that may worsen when standing or walking. The skin over the affected area can feel warm and appear red or discolored, and surface veins may look more prominent. DVT in the arm is less common, but it can occur. This is especially true around catheters or after intense, repeated arm use. It may cause swelling, heaviness, and color changes in the arm or shoulder. Not all DVTs cause obvious symptoms, so if you have new one-sided swelling—especially after travel, surgery, or immobilization—contact a vascular specialist promptly. If you develop sudden chest discomfort, shortness of breath, coughing up blood, or feel faint, call 911.
How DVT is diagnosed
Evaluation starts with your symptoms and risk factors, followed by a focused exam. Duplex ultrasound is the first-line, noninvasive test to confirm or rule out a clot in the leg or arm. In select situations—such as when a pelvic or abdominal clot is suspected or ultrasound is inconclusive—advanced imaging may be used. A D‑dimer blood test can help rule out Deep Vein Thrombosis in low-risk cases, but imaging is required to make a diagnosis.
Treatment and what to expect
For most patients, treatment begins with blood thinners to keep the clot from growing while the body gradually dissolves it. Direct oral anticoagulants are commonly used; low‑molecular‑weight heparin is preferred in some situations such as pregnancy and certain cancers. Treatment duration is usually at least three months and may be longer if the clot was unprovoked or risk factors persist. In select patients with extensive, very symptomatic clots in the larger veins of the thigh and pelvis, minimally invasive catheter-based therapies to remove or dissolve clot may be considered, sometimes followed by stenting if an underlying narrowing such as May‑Thurner syndrome is discovered.
Your specialist will help weigh the benefits and risks based on your anatomy, symptoms, and bleeding risk. Symptom relief strategies can help reduce discomfort and prevent long-term vein damage. These strategies include leg elevation, early guided walking after starting anticoagulation, and using compression as advised. This long-term damage is called post-thrombotic syndrome.
Prevention you can start today
Moving regularly is the simplest way to lower risk. On long trips, get up to walk or do calf raises every 30 to 60 minutes, and stay hydrated. Avoid prolonged bed rest when possible, maintain a healthy weight, and talk with your clinician about your risks before surgery, during pregnancy and the postpartum period, or if you use estrogen-containing medications. If you’ve had a prior DVT, ask your specialist about a prevention plan for future procedures or long travel.
Care at Coastal Vascular Center
When you visit Coastal Vascular Center, you’ll receive a prompt, thorough evaluation that focuses on fast, accurate diagnosis and a personalized, least‑invasive‑first care plan. We commonly begin with on‑site duplex ultrasound and, if a clot is found, start appropriate anticoagulation and symptom management. If your clot is extensive or your symptoms are severe, we discuss whether you may benefit from an advanced endovascular option, and we coordinate closely with your other clinicians to manage risk factors and recovery. We accept many insurance plans. Coverage can vary, so the best way to confirm your benefits is to call our office. Our team will check for you.
About Dr. Divyang C. Ayar
Coastal Vascular Center is led by Dr. Divyang C. Ayar, a board‑certified radiologist specializing in vascular and interventional radiology and an Endovascular Diplomat with the American Board of Vascular Medicine. He trained at the University of Alabama for medical school and residency and completed a fellowship at Vanderbilt University. With more than 20 years of experience and longstanding membership in the Society of Interventional Radiology, Dr. Ayar is known for compassionate, results‑focused care. Learn more about his background at coastalvascular.net/dr-ayar/.
Locations and how to reach us
We care for patients at two convenient locations: 8619 Broadway St., Suite 105, Pearland, TX 77584, and 201 Oak Drive South, Suite 105, Lake Jackson, TX 77566. To schedule an evaluation or confirm insurance coverage, call 713‑999‑6056. Same‑ or next‑day appointments may be available.
Frequently Asked Questions
Deep vein thrombosis is a blood clot in a deep vein, most often in the calf, thigh, or pelvis. It can cause leg swelling, tightness, and pain, and it requires medical care to prevent complications and protect long-term vein health.
New, one-sided leg swelling with a feeling of tightness or heaviness is the most common sign. You may also notice redness or warmth over the area, calf or thigh tenderness (especially when standing or walking), and more prominent surface veins. Some DVTs cause few or no symptoms—new one-sided swelling should be evaluated.
Yes. Even if symptoms are mild, treatment helps prevent the clot from growing and lowers the risk of serious complications. Your specialist will tailor therapy based on the clot’s location, your risks, and your medical history.
If you have a new DVT, postpone long trips until your treatment plan is underway and your clinician says it’s safe. For future travel, move or stretch every 30–60 minutes, stay hydrated, avoid excess alcohol, and consider compression if advised.
Pregnancy and the six weeks after delivery increase DVT risk. New one-sided leg swelling, pain, or warmth should be evaluated promptly. If treatment is needed during pregnancy, we typically use medications that are safe for you and your baby and coordinate closely with your obstetric team.
