What Is an Embolism, and How Can It Be Prevented?

Deep vein thrombosis (DVT) is the formation of a blood clot in the deep veins. This article examines the difference between DVT and fat embolism syndrome, risk factors, evidence-based prevention (a Cochrane systematic review), and warning signs.

What Is Deep Vein Thrombosis (DVT)?

Deep vein thrombosis (DVT) is the formation of a blood clot in the body’s deep veins, usually in the legs. These clots can cause inflammation, pain and swelling. If they break free and travel to the lungs, they can cause a pulmonary embolism, which is a medical emergency. To learn more about the surgical context referred to in this article, you can read the guide to nose surgery (rhinoplasty).

The Difference Between DVT and Fat Embolism Syndrome

Important: Deep vein thrombosis (DVT) is different from fat embolism syndrome. DVT involves blood clots that form in the veins. Fat embolism syndrome, however, is more commonly seen after severe injuries, particularly fractures of long bones, and is associated with fat particles entering the bloodstream; pancreatitis is a rare reported non-traumatic cause. These two conditions have different mechanisms and risk factors and should not be confused with one another.

Main Risk Factors for Deep Vein Thrombosis

According to a review published in 2025, deep vein thrombosis arises from a diverse and overlapping range of risk factors, including:

• Genetic and inherited factors: Certain genetic disorders, such as deficiencies of antithrombin, protein C or protein S, or factor V Leiden, can increase the risk of clot formation. A nationwide cohort study in Denmark has also shown that alpha-1 antitrypsin deficiency is associated with an increased risk of deep vein thrombosis and pulmonary embolism.
• Surgery and trauma: Major operations, particularly abdominal, pelvic or orthopaedic surgery, can increase the risk of DVT, both because of immobility during and after surgery and because of changes in the blood’s clotting system.
• Immobility: Prolonged lack of movement, particularly during hospital stays, long journeys or bed rest, can slow blood flow and increase the risk of clot formation.
• Obesity: A high body mass index (BMI) is associated with an increased risk of DVT.
• Pregnancy and childbirth: Pregnant women are at higher risk because of hormonal changes and pressure on the veins.
• Hormone therapy: Taking combined oral contraceptives or hormone replacement therapy can increase the risk.
• Age: The risk of DVT increases with age.
• Cancer: Patients with cancer are at higher risk because of changes in the blood’s clotting system.
• Chronic diseases: Heart failure, inflammatory diseases and other chronic medical conditions can increase the risk.

An international observational study of 7,754 women aged 18 to 55 with a history of a first venous thromboembolism (VTE) event associated with transient risk factors examined the risk of recurrent VTE, including DVT or pulmonary embolism. These findings apply to the selected study population and do not represent the risk of a first clot in all young women.

Preventing Deep Vein Thrombosis

A Cochrane systematic review and meta-analysis examined 34 studies and 14,931 participants, mainly hospitalised surgical or trauma patients. The certainty of the evidence varied depending on the outcome and comparison; it was low for pulmonary embolism and very low for bleeding. The review reported that:

• Combining intermittent pneumatic compression (IPC) with pharmacological prophylaxis, compared with either method alone, reduced the incidence of deep vein thrombosis and pulmonary embolism in this population.
• Adding pharmacological prophylaxis to IPC was associated with increased bleeding; in contrast, no significant increase in bleeding was observed when IPC was added to medication. The certainty of the evidence on bleeding was very low, and the absence of a statistically significant difference does not prove the absence of risk.
• Graduated compression stockings and early mobilisation are also recognised as mechanical measures.

Important: This evidence mainly concerns hospitalised surgical or trauma patients. The choice of prophylaxis and the extent to which it is needed depend on each patient’s risk assessment and the treating physician’s decision; no method is universally recommended for everyone, and extrapolating these results to outpatients or low-risk operations is unfounded. This article does not provide pharmacological prophylaxis instructions or medication doses for any particular individual.

In a single-centre, quasi-experimental study of immobilised neurosurgical patients, a nurse-led, team-based care protocol, including dynamic risk assessment, standardised mechanical prophylaxis, education and early mobilisation, was associated with a reduction in the incidence of DVT. This finding represents only one experience at one centre and in a particular population and should not be treated as a universal recommendation.

Warning Signs

If symptoms consistent with DVT develop, prompt medical assessment is needed; avoid diagnosing yourself on the basis of symptoms alone:

• Sudden swelling in one leg
• Pain or tenderness in the leg, particularly when standing or walking
• Warmth, redness or a change in the colour of the skin of the leg

The following symptoms may indicate a pulmonary embolism, which is a medical emergency; if they occur, call emergency services immediately (115 in Iran):

• Sudden shortness of breath
• Chest pain that worsens when breathing
• Coughing up blood
• Palpitations, dizziness or fainting

The Connection With Rhinoplasty

The risk of venous thrombosis after any operation depends on individual factors, the duration of the operation, the degree of immobility and medical history, and should not be estimated solely from the name of the operation. Awareness of general symptoms and risk factors can help you discuss your personal risk with your physician. For this purpose, you can read the guides to:

• Possible complications of rhinoplasty
• Pre-rhinoplasty preparations and checklist
• Care after rhinoplasty

Important Points

This article is for educational purposes only and is not a substitute for personalised medical advice, diagnosis or treatment. If you have a specific concern about DVT risk, prevention or symptoms, please consult your physician.