In short
Graft infection is a serious complication that can occur when synthetic materials used to repair or replace blood vessels become infected by bacteria or other microorganisms. Though uncommon, affecting roughly 1 to 5 out of every 100 people who receive a vascular graft, this condition requires immediate attention and can be life-threatening if left untreated.
What Is Graft Infection?
A vascular graft (a tube usually made of synthetic material) is used in surgery to repair or replace damaged blood vessels, particularly the aorta (the largest artery carrying blood from the heart) or other major arteries. When bacteria, viruses, or fungi attach to this artificial material and multiply, they cause what is known as a graft infection.
The infection can flow through the bloodstream and may cause severe illness with fever, chills, and weight loss. Unlike natural blood vessels, which rarely get infected, these synthetic grafts are foreign bodies that are more vulnerable to infection.
How Common Is Graft Infection?
Graft infections occur in approximately 1 to 5 percent of patients who receive a vascular graft. The exact number is difficult to determine because infections can appear many years after the surgery was performed.
The risk of infection varies depending on several factors. Infections are more likely when the surgical incision is made in the groin area, when the procedure is performed as an emergency, or when a patient needs a second operation to fix or replace a graft. Infection following endovascular stent placement (a less invasive procedure where a mesh tube is inserted through a small incision) is considered very rare.
When Does Graft Infection Occur?
Graft infections can develop at different times after surgery, and the timing often indicates how the infection started.
Early infections typically occur within the first four months after surgery. These infections are usually caused by more aggressive bacteria such as Staphylococcus aureus, E. coli, Pseudomonas, Klebsiella, Proteus, and Enterobacter. Early infections tend to cause noticeable symptoms like fever, increased white blood cell count, infection at the entry site (often the groin), and problems with how the graft is working.
Late infections develop after four months and can appear many years following the original surgery. These can happen in two ways. First, bacteria from an infection elsewhere in the body (such as a severe urinary tract infection or infected heart valves) can travel through the blood and attach to the graft. Second, the graft material can become infected with bacteria that were present at the time of surgery but grow very slowly. Late infections caused by less aggressive bacteria like coagulase-negative staphylococci often develop gradually with subtle symptoms such as a false aneurysm, bone infection, or kidney swelling.
How Do Grafts Become Infected?
The most common way a graft becomes infected is during the surgery itself. Bacteria can contaminate the graft from the surgical team or from bacteria already living on the patient's skin.
Research shows that most patients undergoing artery surgery carry coagulase-negative staphylococci bacteria on their skin. If a patient stays in the hospital for a long time before surgery, their risk of being colonized by hospital bacteria increases.
Emergency surgeries carry a higher infection risk, with rates reported as high as 7.5 percent. Other possible sources of infection during surgery may include dividing lymph nodes, infected fluid that collects around the aorta during surgery, or infected blood clots, though evidence for these sources is not conclusive.
For stent graft infections, groin infections are less commonly the cause. Instead, any infection that occurs around the time of surgery (most often urinary tract infections) or placing the stent graft in an already infected area may lead to infection. Roughly one-third of stent graft infections appear to have no clear connection to the procedure itself.
What Bacteria Cause Graft Infections?
Several types of bacteria and other microorganisms can cause graft infections.
Staphylococcus bacteria are responsible for approximately 35 percent of all graft infections. Staphylococcus aureus is more likely to cause early infections, while coagulase-negative staphylococci (such as S. epidermidis) are more often responsible for late infections that develop slowly.
Gram-negative bacteria like Pseudomonas aeruginosa and Escherichia coli, Salmonella species, streptococci, and enterococci can also cause infections. In about 25 percent of cases, more than one type of bacteria is found. Anaerobic bacteria (those that grow without oxygen) are rarely involved but are more common with aortic grafts.
Less commonly, infections can be caused by intracellular or hard-to-grow organisms like Coxiella burnetii and Treponema pallidum, various Mycobacterium species, or Candida fungi. Though rare, these infections are associated with high rates of serious complications and death.
What Are the Symptoms?
The symptoms of graft infection vary depending on when the infection develops and where the graft is located.
Some people may have no symptoms at all. Others may experience flu-like symptoms including fever, chills, night sweats, body aches, muscle pain, or unintended weight loss.
If an old surgical incision becomes infected, you might notice cloudy or foul-smelling fluid draining from it. The area around the graft may show pain, warmth, redness, or swelling. In some cases, blue spots may appear on the feet.
When infection occurs within four months of surgery, symptoms often include increased white blood cell count, fever, infection at the entry site (usually the groin), and problems with how the graft functions.
If infection develops more than four months after surgery, symptoms may be less noticeable and include a false aneurysm (a collection of blood outside the blood vessels), bone infection, or kidney swelling.
How Is It Diagnosed?
If you develop a fever, chills, or notice drainage from a surgical incision—no matter how long ago the surgery was—you should seek medical help immediately.
Your doctor will perform a thorough examination and order various tests to confirm whether your graft is infected.
Blood tests may include a white blood cell count to check for signs of infection. Imaging tests help doctors see what is happening inside your body. These may include a computed tomography (CT) scan, which uses X-rays to create detailed pictures, or an ultrasound, which uses sound waves to create images.
In some cases, a white blood cell scan may be performed. In this test, white blood cells are removed from your blood, marked with a special tracer, and returned to your bloodstream. The tracer helps identify areas of infection.
A specialized imaging test called PET/CT using 18F-FDG has proven highly accurate for diagnosing vascular graft infections. This test combines two types of imaging to show both the structure and function of tissues. It can precisely locate increased activity in infected areas and distinguish between infection of the graft itself and infection of surrounding soft tissues. Studies have shown this test to be 93 percent sensitive and 91 percent specific for detecting graft infections.
How Is It Treated?
Treating graft infections requires a team approach involving surgeons, radiologists, microbiologists, infectious disease specialists, anesthesiologists, and intensive care specialists.
Treatment typically combines two main approaches: antibiotics and surgery.
Antibiotic treatment is a key part of managing graft infections. In some cases, patients may need to take antibiotics for several months or even for the rest of their lives.
Surgical treatment often involves removing the infected graft and replacing it with a new one, or creating a surgical bypass around the infected graft. Whether the graft can be preserved or must be removed depends on each individual case and is decided by the medical team.
If infected grafts are not removed, many will slowly break down and can rupture, causing severe bleeding that may result in limb loss or death.
What Are the Possible Outcomes?
Graft infection is a serious condition with significant risks. Approximately one-third of all patients with vascular graft infections die from complications related to the infection, with the highest death rates occurring when the infection involves an aortic graft.
Among those who survive an infected aortic graft, as many as 75 percent require amputation of a limb. The risk of amputation is highest when the infection affects grafts in the lower parts of the body, such as the legs.
Early detection and prompt treatment are crucial for improving outcomes and reducing the risk of these serious complications.
