Deep vein thrombosis (DVT) happens when there’s a blood clot in one or more of the deep veins in your body. Various factors could put you at risk for thrombosis. You may be more likely to have a DVT if you:
- Are over the age of 60
- Sit for long periods of time or are on bed rest
- Had an injury or surgery
- Are pregnant
- Are overweight or have obesity
- Smoke
- Use birth control pills or hormone replacement therapy
- Have cancer, inflammatory bowel disease, or heart failure
- Have a family history of DVT or pulmonary embolism (PE)
If you get an infection, that also increases your risk for DVT. The infection causes inflammation that can trigger the process that makes a clot form.
To understand the connection between thrombosis, inflammation, and infection, you first need to know about your body’s coagulation or clotting system. Your body normally creates blood clots to help heal injuries and seal off bleeding.
But sometimes, your clotting system can cause dangerous blood clots, like DVTs, that your body doesn't need. This may block the flow of blood to important parts of your body. This can affect any part of your body. With deep vein thrombosis, this usually happens in your lower leg, thigh, pelvis, or sometimes your arm.
Your body’s coagulation/clotting system, immune system, and inflammation responses all work together. If you get injured or have a disease, these systems will respond to keep you healthy. Since they interact, a change in one of these responses can throw off the balance of another. Inflammation and infection play a big role in the formation of possibly harmful blood clots.
What Types of Infections Can Lead to Thrombosis?
All types of infections can result in thrombosis, but certain ones are more likely to cause complications. They include:
- Pneumonia
- Strep throat infection
- Staph infection on your skin
- Asymptomatic urinary tract infection
- Oral infections (like periodontitis or gingivitis)
- Intra-abdominal infections
- Bloodstream infections
- The virus that causes COVID-19 (during the pandemic, experts found that having this infection is a risk factor for DVT)
Infection-related thrombosis can also happen in children. Some illnesses in kids could lead to this condition:
- Sepsis, when your body harms its own tissue
- Necrotizing enterocolitis, a serious illness that affects premature infants’ intestines
- Otitis media, an infection or inflammation in your middle ear
- Pulmonary infections caused by respiratory syncytial virus (RSV)
You’re at the highest risk for forming clots when your infection is active or in the weeks right after.
How Can an Infection Cause Thrombosis?
When you have an infection, it creates inflammation in your body. This makes your blood more likely to clot.
The risk of developing a DVT is based on the level of inflammation in your body. More severe infections lead to higher amounts of inflammation. In turn, this can put you at a greater risk of clotting/thrombosis. During infections, chemicals are released from white blood cells to try to control the infection. If there’s too much of this, you may develop inflammation and organ damage. Once this happens, you’re more likely to have a blood clot that can lead to thrombosis.
Experts are studying whether other traditional DVT risk factors play into your likelihood of thrombosis. They are looking at the relationship between infection-related thrombosis and:
- Whether you smoke
- Your lipid levels
- How active you are (inactive lifestyles may be a risk factor)
What they found was no matter your risk factors, infections can still lead to thrombosis.
What Are DVT Warning Signs?
If you think you have symptoms of DVT, contact your doctor. You might notice:
- Pain in your leg. This tends to start in your calf. It might feel like cramping or soreness.
- Red or different colored skin on your leg
- Swelling in your leg
- A warm feeling in your leg
Some DVTs happen without any symptoms at all.
What Treatments May Help Infection-Related Thrombosis?
Experts are looking into ways to prevent or limit thrombosis from infections. If you have sepsis, your doctor will most likely give you low molecular weight heparin to avoid DVT. But there’s currently no overall treatment to prevent thrombosis for people with infections.
An ideal treatment for this would include a plan that can:
- Control your risk of thrombosis
- Not put you at risk for bleeding
- Not lead to worsened infection
Doctors and researchers are working in these areas to help prevent infection-related thrombosis:
Coagulation and fibrinolysis. In cases of sepsis, doctors may give you blood clotting factors to help stop blood clots. But in clinical trials, some of these medications didn’t show as many benefits. They also put people at a higher risk of bleeding.
Heparin, a blood thinner, can treat blood clotting and can lower inflammation. This drug also tends to have a low risk of bleeding.
Doctors use this heparin to prevent and treat blood clot complications. But there isn’t any research about heparin specifically in infection-related situations.
Inhibiting platelet activity. Platelets are cells that circulate in your blood and combine when they find damaged blood vessels. Platelets' actions are important in infection-related thrombosis. Infection and inflammation can both activate your platelets. This can lead to blood clots.
To stop inflammation and infection and avoid blood clots, your doctor may put you on a treatment that limits platelet activity.
Neutrophil activation. This process will boost your body’s inflammatory response and can harm normal tissue. These white blood cells play a role in protecting your body against infection from outside bacteria. They move to areas of inflammation and release chemicals called cytokines. This process can control the immune system, infection, and your body’s inflammatory process. These cells’ main function is to clear infection. But as they do that, they can also cause a lot of inflammation and harm to the tissue in that area. This is another area where treatments are being directed to help prevent blood clots.
While some of these treatments may help with thrombosis, they also have downsides. They may affect your immune response or lead to bleeding.
Experts continue to research for ways to prevent and treat DVTs that don’t lead to unwanted side effects.