ConditionHeart & circulation
Postoperative Thrombosis (Blood Clots After Surgery)
Postoperative thrombosis is a blood clot that forms in a vein after surgery, most often a deep vein thrombosis (DVT) in the leg, which can travel to the lungs as a pulmonary embolism (PE). Surgery raises clot risk because of tissue injury, reduced movement and changes in blood clotting. Risk is highest after hip and knee replacement, major cancer surgery and long operations, and remains raised for up to 3 months. Early walking, compression devices and preventive blood thinners greatly reduce the risk.
Also called: Post-surgery blood clots, postoperative DVT, surgery-related venous thromboembolism, postoperative VTE
At a glance
- What it is
- A clot in a vein (DVT) or lung (PE) developing after surgery.
- When
- Most often within the first 2 to 4 weeks, but risk lasts up to about 12 weeks.
- Highest risk
- Hip and knee replacement, hip fracture surgery, major abdominal or pelvic cancer surgery, spine and trauma surgery.
- Signs
- Leg swelling, pain and warmth; sudden breathlessness, chest pain or coughing blood.
- Prevention
- Early mobilization, compression devices, preventive anticoagulants for a set period.
When to get help
Call 911 or go to the ER
- Sudden shortness of breath, sharp chest pain worse on breathing in, coughing up blood, a racing heart or fainting after surgery: call 911 or your local emergency number
- A leg that is suddenly very swollen, pale or blue and extremely painful
See a doctor within a day or two
- New swelling, pain, tenderness, warmth or redness in one calf or thigh in the weeks after surgery
- Arm swelling on the side of an IV line or PICC line
- Bleeding that will not stop, black stools or blood in urine while on preventive blood thinners
Book a routine appointment
- Questions about how long to take preventive blood thinners or wear stockings
- A personal or family history of clots before planning surgery
Why surgery causes blood clots
All three classic triggers for clots (Virchow's triad) occur around surgery:
- reduced blood flow: lying still during and after surgery, anesthesia relaxing veins, and immobilization in casts or braces
- vessel injury: direct damage to veins during orthopedic, pelvic or vascular surgery
- increased clotting: tissue injury releases substances that activate clotting for days to weeks
Risk factors
Surgery-related
| Higher risk | Lower risk |
|---|---|
| Hip and knee replacement, hip fracture repair | Short day-case procedures under 30 to 45 minutes |
| Major cancer surgery (abdomen, pelvis) | Minor surgery in mobile, healthy people |
| Spinal, trauma and neurosurgery | |
| Long operations, general anesthesia | |
| Prolonged immobilization afterward |
Patient-related
- previous DVT or PE
- active cancer or cancer treatment
- inherited or acquired thrombophilia
- age over 60
- obesity
- estrogen-containing contraception or hormone therapy
- pregnancy or recent birth
- heart failure, lung disease, inflammatory bowel disease
- varicose veins, dehydration and smoking
Before surgery, doctors use risk scores (such as the Caprini score) to decide which preventive measures you need.
Signs and symptoms
Deep vein thrombosis
- swelling of one leg, ankle or calf
- pain, cramping or tenderness, worse on standing or walking
- warmth and redness
- visible surface veins
Some swelling after leg surgery is normal, which can make DVT harder to spot. New or increasing swelling and calf pain should be checked.
Pulmonary embolism
- sudden breathlessness
- chest pain, especially when breathing in
- coughing blood
- fast heartbeat, dizziness or fainting
See deep vein thrombosis and pulmonary embolism.
Diagnosis
- compression ultrasound of the leg veins for suspected DVT
- CT pulmonary angiogram for suspected PE
- D-dimer is less useful after surgery because it is usually raised anyway
- blood tests and ECG
Prevention
Mechanical methods
- early mobilization: getting up and walking as soon as safely possible after surgery is one of the most effective measures
- leg exercises in bed: flexing ankles, circling feet, tightening calf muscles
- intermittent pneumatic compression devices: inflatable sleeves that squeeze the legs during and after surgery
- graduated compression stockings in some settings, when fitted correctly
Medicines
- low-molecular-weight heparin injections (such as enoxaparin)
- direct oral anticoagulants (rivaroxaban, apixaban) after hip and knee replacement
- aspirin after hip and knee replacement in selected lower-risk patients
- unfractionated heparin in some cases, such as kidney failure
Duration is usually 10 to 14 days, extended up to about 35 days after hip replacement, hip fracture and major abdominal or pelvic cancer surgery, according to guidelines. Take preventive medicines exactly as prescribed for the full course, even after you go home.
Around surgery
- your team will advise whether to stop estrogen-containing pills before major surgery
- stay hydrated
- stop smoking
Treatment
If a clot develops, treatment follows standard DVT and PE care: anticoagulants for at least 3 months. Because surgery is a temporary, "provoked" risk factor, 3 months of treatment is often enough. Bleeding risk at the surgical site is balanced carefully, particularly in the first days after surgery.
Complications
- pulmonary embolism, which can be fatal
- post-thrombotic syndrome: long-term leg swelling, pain and skin changes
- recurrent clots
- bleeding from anticoagulants
Frequently asked questions
What are the signs of a blood clot after surgery?
Watch for swelling, pain, warmth or redness in one leg, especially the calf. Signs of a clot in the lungs include sudden shortness of breath, chest pain on breathing in, coughing blood and a racing heart, which need emergency care.
How long after surgery are you at risk for blood clots?
The risk is highest in the first 2 weeks but remains raised for up to about 12 weeks after major surgery, especially orthopedic and cancer surgery. Keep moving and complete any prescribed preventive medicine.
How can I prevent blood clots after surgery?
Walk as soon as you are allowed, do ankle and calf exercises, stay hydrated, use compression devices or stockings if prescribed, and take preventive blood thinners exactly as directed for the full course.
Do I need blood thinners after surgery?
It depends on the type of surgery and your personal risk. Many people having major orthopedic, abdominal, pelvic or cancer surgery are given preventive anticoagulants. Your surgical team will assess your risk and decide.
Sources
This guide was written from current patient and clinical guidance, including:
- American Society of Hematology: 2019 Guidelines for Management of VTE: Prevention of VTE in Surgical Hospitalized Patients
- American College of Chest Physicians (CHEST): Prevention of VTE in Nonorthopedic and Orthopedic Surgical Patients
- American Academy of Orthopaedic Surgeons: Preventing venous thromboembolic disease in patients undergoing elective hip and knee arthroplasty
- NICE Guideline NG89: Venous thromboembolism in over 16s: reducing the risk of hospital-acquired DVT or PE
- CDC: Healthcare-associated venous thromboembolism