Mycotic Aneurysm

What is Mycotic Aneurysm?

A mycotic aneurysm is a condition where an artery wall expands due to an infection. The name ‘mycotic’ was given by William Osler, who noticed its look was similar to a type of fleshy fungus. However, the name doesn’t mean it’s caused by a fungi. In fact, most of these aneurysms are because of bacterial infections. That’s why a more accurate name can be an ‘infected aneurysm’. A related term, infectious aortitis, is when there’s an infection in a vessel but no expansion of the vessel wall. An infected aneurysm often results from a previous systemic infections with bacteria in the blood or comes from direct infection of the wall of a blood vessel. This could happen in individuals with a pre-existing aneurysm or atherosclerotic plaques, which are deposits that narrow the arteries. This is especially common in people who use IV drugs.

People at higher risk include those with weak immune systems, such as folks with HIV, diabetes, those who use high doses of specific medications like glucocorticoids, and those with cancer undergoing chemotherapy. Vessels in the legs (femoral), abdomen (aorta), and within the body (like the superior mesenteric and splenic arteries) are typically involved. Over time, the mycotic aneurysm expands, sometimes causing a pseudoaneurysm (where the vessel wall contains a rupture), rupture, bleeding, sepsis (a serious infection that affects the entire body), and failure of multiple organs. Mycotic aneurysms present a significant challenge to vascular surgeons because of the high risk of death during surgery.

What Causes Mycotic Aneurysm?

Mycotic aneurysms are basically infections in the blood vessels that cause them to widen and form a sac or bulge. Here are some of the reasons why these might occur:

1. Bacteremia: This is a condition where you get bacteria in your blood. If you have a pre-existing injury in your blood vessels (common in older people because of conditions like atherosclerosis or an existing aneurysm), bacteria can easily infect the inner layer of the blood vessel (the intima) during a severe infection or a condition where the entire body responds to an infection (known as sepsis). It most commonly affects the aorta (the body’s main artery) because of the prevalence of atherosclerosis and aneurysms there.

2. Local Injury and Bacterial Inoculation: Infections can occur in the blood vessel wall if bacteria enter them because of a local injury. Such injuries could be due to intravenous (IV) drug abuse, accidental injuries, or procedures done for treatment that may inadvertently damage the blood vessels (iatrogenic causes). This is usually seen in the arteries in the limbs, like the femoral (thigh), common iliac (pelvis), or subclavian and carotid arteries (neck).

3. Local Spread: If an infection exists nearby, it can sometimes extend to local arteries causing them to become inflamed. This is seen in conditions such as vertebral osteomyelitis (spine bone infection), and issues inside the abdomen like appendicitis, pyelonephritis (kidney infection), and cholecystitis (gallbladder inflammation).

4. Septic Emboli: If you have infective endocarditis, a condition where the inner layer of your heart is infected, it can lead to the creation of septic emboli. These are basically infected blood clots that travel to the smaller blood vessels in the body (vasa vasorum) causing inflammation and subsequently, mycotic aneurysms. The emboli often involve multiple sites, and tend to affect the arteries inside the brain at their branching points.

Risk Factors and Frequency for Mycotic Aneurysm

Infectious aortic aneurysms are rare, accounting for only 0.7 to 3% of all aortic aneurysms. They are more likely to occur in men, particularly those who smoke or have diabetes. This is because these conditions increase the risk of atherosclerosis, which is a major cause of aneurysms. The average age of patients with an infectious aortic aneurysm is around 65 years.

The arteries most commonly affected are the femoral arteries, aorta, splanchnic (which includes the superior mesenteric, hepatic, and splenic arteries), and cerebral arteries.

There are several types of bacteria that can cause these aneurysms. In Western countries, the most common ones are Staph. aureus (28%), Salmonella spp (15%), and Pseudomonas aeruginosa (10%). In contrast, Salmonella is the most frequently reported bacteria in Asian countries.

There have also been individual case reports of specific circumstances leading to these aneurysms. For instance, some patients have developed coronary mycotic aneurysms after having a stent placed, and others have developed renal artery mycotic aneurysms after receiving a renal transplant. A further 2-10% of people with infective endocarditis, particularly those with left-sided endocarditis, may develop an intracranial mycotic aneurysm.

Signs and Symptoms of Mycotic Aneurysm

An infected aneurysm can present differently based on the infection’s severity, the patient’s other health conditions, and the aneurysm’s location. Certain factors, like intravenous drug use, recent medical procedures, weakened immune system or prior incidents of endocarditis, can make a person more susceptible to an infected aneurysm.

The main signs of an infected aneurysm include fever, a pulsating mass, localized pain, and inflammation. Depending on the artery affected, this could appear as back pain (if it’s the aorta) or headaches (if it’s the brain vessels). However, these symptoms are quite common and non-specific, and as a result, some patients may remain undiagnosed until they show severe symptoms of sepsis, blood clotting, bleeding, or rupture of the aneurysm.

If the infection spreads locally, it could lead to complications like a psoas abscess, which causes pain in the side, a limp, and fever; osteomyelitis in the vertebrae; difficulty swallowing; a hoarse voice due to laryngeal nerve impact; and coughing up blood. Another possible complication is the formation of a fistula, which could cause high-output heart failure or expanding hematoma.

A physical examination could also reveal signs of local inflammation, such as a tender hardened mass and a whirling sound heard during examination, which is seen in half of the infected aneurysm cases. If cerebral aneurysms are present, they could lead to a stroke or subarachnoid hemorrhage.

Testing for Mycotic Aneurysm

If you have risk factors or symptoms that suggest you might have a mycotic aneurysm, your doctor will conduct a thorough examination to confirm. It’s worth noting that there is no specific process or criteria for detecting mycotic aneurysms. Instead, your doctor will likely rely on a combination of physical signs, lab tests, imaging studies, and findings from any surgeries to determine if you have this condition.

Some of the symptoms that might suggest a mycotic aneurysm include fever, unusual physical signs, being immunocompromised, having risk factors for hardened arteries, and ongoing infections. Typical lab results may show high levels of inflammation, white blood cells, or positive blood cultures, which mean bacteria are present in your bloodstream.

It’s also noteworthy that the presence of bacteria is confirmed in 50-85% of mycotic aneurysm cases through lab testing.

Imaging studies are very important and give the most reliable indicators. Some signs that could suggest a mycotic aneurysm include a bulging, irregularly shaped blood vessel, inflammation around the blood vessel visible with contrast enhancement, bubbles of gas inside or around the blood vessel, or a collection of fluid around the aneurysm.

The most common type of imaging used at the beginning to identify aortic aneurysms is contrast-enhanced CT scans, but MR angiography can also be used as an alternative. A transthoracic echo is the preferred method for looking at coronary aneurysms. However, the technique is more invasive. Nuclear scans have been largely used to detect graft infection. If there is a suspicion of infectious endocarditis, your doctors may utilize extensive angiography and other imaging studies since this condition can result in multiple aneurysms.

Once your treatment, typically using antibiotics, is underway, your doctor will perform serial inflammatory marker testing and imaging studies before and after any needed surgeries to monitor your progress and ensure the infection is resolving.

Treatment Options for Mycotic Aneurysm

Patients suffering from an infection need a lengthy period of antibiotics that are specific to their condition and the bacteria causing it. This treatment typically lasts around 6 to 8 weeks, but if the infection is persistent, the duration may be extended. How well the treatment is working is tracked by regular monitoring of white cell counts, inflammation indicators, the disappearance of fever, and stable vital signs. Initial antibiotics typically include vancomycin along with another antibiotic effective against gram-negative bacteria, which include types like salmonella.

Ultimately, to effectively tackle the infection, surgical procedures are needed to remove all infected tissue. The nature of this surgical procedure can vary and depends on where the infection is located, how extensive the infection is, the overall health of the patient, and the surgeon’s judgement.

For infections located in smaller, peripheral arteries and splanchnic vessels, a commonly chosen approach is to tie off and remove the infected part of the artery. When dealing with medium-sized vessels like the renal, visceral, carotid or femoral arteries, sections of other vessels, such as the iliac artery or saphenous vein, can be used to replace the infected part. Large vessels such as the aorta that aren’t badly infected can be managed by replacing the infected section with an uninfected graft, which is then wrapped in tissue from the omentum (a large fold of tissue in the abdomen) to lessen the likelihood of further infection. If there’s persistent pus production or extensive infection around the aorta, an extra-anatomic bypass might be needed.

If emergency surgery was needed to place a graft in an infected surgical site, long term antimicrobial therapy is considered to prevent further infection.

It’s worth noting that the risk of death during or soon after open surgery is high, around 1 in 5 patients. This has led to increased interest in less invasive endovascular therapies, which might be a better choice for high-risk patients, or used as an interim measure before definitive surgery in patients with severe sepsis. While some studies suggest higher short-term death rates with open surgery when compared to endovascular repair, the long-term outcomes are similar.

If an infection occurs after either type of repair, it should be treated with systemic antibiotics.

What else can Mycotic Aneurysm be?

When trying to identify a mycotic aneurysm – a type of blood vessel swelling caused by infection – doctors must consider several other conditions that can present similar symptoms. These conditions involve various organ systems, making the diagnosis complex. Here are some possible diagnoses that must be considered:

• Cellulitis — a common skin infection
• Atherosclerotic aortic aneurysm — a slow-developing swelling of the aorta, the main blood vessel in the body, often indicated by the presence of calcium deposits and lack of fever or other signs of infection
• Pyelonephritis — a kidney infection, specifically thinking of a renal artery mycotic aneurysm in transplanted kidneys
• Inflammatory aortitis and aneurysm due to vasculitides — inflammation of the aorta and blood vessel swelling as a result of inflammation of the blood vessels
• Intracranial mycotic aneurysms — a specific type of mycotic aneurysm in the brain, which can present symptoms similar to meningitis, septic thrombophlebitis, or orbital cellulitis.

By considering these possibilities, healthcare providers can more accurately pinpoint the issue and provide appropriate treatment.

What to expect with Mycotic Aneurysm

Survival from an aneurysm largely depends on where it is located. Infected aortic aneurysms, or dangerous bulges in the aorta (the main blood vessel in your body), usually have poor outcomes. Without treatment, these aneurysms can almost always lead to death. Some factors indicating poor outcomes include being female, being unstable or in shock or having a fever during surgery, having a weak immune system, extensive involvement of the aorta and areas around the aorta.

Studies have shown that endovascular repair, a less invasive method that involves fixing the aneurysm from within the blood vessel, can lead to better survival rates compared to traditional open surgery.

In the long term, outcomes can depend on the type of treatment procedure. However, patients who respond well to medical treatment generally have good survival rates and do not have long-term disabilities. On the other hand, patients who don’t manage to clear the infection completely or those with reinfected grafts, (which are synthetic or natural materials used to replace a part of the blood vessel), have a poor prognosis. The death rate is nearly 100% if the infected graft is not removed.

Possible Complications When Diagnosed with Mycotic Aneurysm

If aneurysms are not treated promptly, they run the risk of bursting (about 60% cases). This can lead to sepsis, a severe infection that can spread throughout the body, or thrombosis, where a blood clot obstructs a blood vessel. It may also result in distal ischemia, where blood flow to the limbs is reduced, or multiorgan failure, where several organs stop working.

Certain complications can occur when treating aneurysms with in-situ surgical repair. These are usually due to the long duration of the surgery and the resultant lack of blood flow to certain areas. They might include heart attacks, stroke, blood flow issues in the intestines or acute kidney injuries. Long-term complications can be graft failure, which is when the blood vessel graft doesn’t work, or paragraft leaks caused by failed connections or fistula formation, which is an unnatural connection between two body parts. Graft infections can be particularly serious, leading to a 100% death rate within two years if not properly managed.

An alternate surgical method, the extra-anatomic bypass, has fewer complications during operation but majority of patients eventually struggle with reduced or blocked blood flow to the limbs or severe cramping.

Common Complications:

• Bursting of aneurysms
• Sepsis
• Thrombosis
• Distal ischemia
• Multiorgan failure
• Heart attacks
• Stroke
• Reduced blood flow to intestines
• Acute kidney injuries
• Graft failure
• Paragraft leaks
• Unnatural connections between body parts
• Severe graft infections
• Limb ischemia or severe cramping with the extra-anatomic bypass method

Recovery from Mycotic Aneurysm

The risk of death during or shortly after open surgery is around 20%. After the operation, 60% of patients experience complications. These might include decreased blood supply or the necessity of limb removal, kidney failure, difficulty in breathing that requires extended use of a breathing machine, and failure of multiple organs.

There are also risks associated with extra-anatomic bypass procedures, including a disruption in the stump attached to the aorta, the potential for limb removal, and re-infection.

Recovering from surgery often requires a long hospital stay, with the average stay being around 58 days. Many patients also require extended physical and occupational therapy, and a slow return to their normal activities.

Preventing Mycotic Aneurysm

Patients are often recommended to stay in the hospital until their symptoms improve or their fever and infection have gone down. During the first phase after their operation, they may be treated in the intensive care unit of the hospital. People who are about to have the operation should also be aware of the risks and possible complications linked to the procedure, along with other treatment options. Furthermore, these patients will need to continue with antibiotic treatments for an extended period, and in some cases, for the rest of their lives. Therefore, they need to be well-informed about this aspect of the care plan.

The following are the instructions for care after the operation:

* It’s best to wear loosely fitting clothes that will not chafe against the surgical wound
* Try to avoid bathing in the bathtub, hot tub, or swimming pool shortly after the operation
* The surgical incision should be cleaned every day with soap and water once it starts healing
* Exchange wound dressings often
* Please refrain from applying any lotions, creams, or traditional medicine to the wound
* It’s recommended to slowly get back to activity as you recover

As most patients are older, they may benefit from seeing physical or occupational therapists.

Mycotic aneurysms, which are blood vessel abnormalities caused by infection, are often linked to hardening of the arteries, a condition known as atherosclerosis. Therefore, individuals with mycotic aneurysms are also encouraged to reduce their risk factors related to this condition. This could include adopting the DASH diet (a diet for lower high blood pressure), stopping smoking, or taking medications like statins (which lower the level of cholesterol in the blood) or aspirin.