**6. Clinical presentation**

Symptoms of mycotic aortic aneurysms are very commonly nonspecific in the initial development of the disease. Patients with MAAs often present with fever of unknown cause. Many series have reported fever as the most common presenting sign of MAAs. These patients with febrile illness frequently present with insidious onset, apathy, weight loss, and general malaise [24].

A high index of suspicion is of great importance in order to avoid delay in diagnosis, as the natural history of most of these untreated mycotic aortic aneurysms is fatality. The most common causes of death in these patients are lethal sepsis or massive hemorrhage due to rupture [24, 31].

A vast majority of patients are symptomatic at the time of diagnosis. Most groups have outlined rates of MAAs as symptomatic on diagnosis involving 93–100% of cases [28, 31]. One of the most common symptoms at the time of initial evaluation is localized pain. When present, pain is most commonly localized in the abdomen, chest, or back. Some groups have reported pain as the most common initial clinical symptom of MAAs, in up to 88% of patients [28, 32]. It has been previously reported that the classic triad of mycotic aortic aneurysms includes fever, pulsatile mass, and back pain. This triad has been described in around 40% of patients [31].

Other manifestations have been described associated to MAAs, including the following:

#### 1.Rupture

Massive hemorrhage may be a sign of MAAs. Some reports have described aortic rupture in MAAs in 50–85% of patients [24, 28, 31].

#### 2.Expanding hematoma

Intraabdominal retroperitoneal hematomas usually produce hypovolemic shock. In cases of infected aortoiliac or associated mycotic femoral aneurysms, superficial expanding hematomas might be seen.

3.Acute ischemia of the lower limbs

Embolization is a common clinical sign that increases limb loss and mortality rates.

4.Mesenteric ischemia

Infected pararenal of thoracoabdominal aortic aneurysms (TAAA) involving the superior mesenteric artery (SMA) may cause acute thrombosis of the SMA or embolization into the distal mesenteric branches, leading to intestinal ischemia.

5.Osteomyelitis

Infection of the aorta may produce contiguous infection of the lumbar or thoracic vertebra. Interchangeably, a bone infection affecting the vertebra may provoke an infection of an aortic aneurysm.

6. Gastrointestinal bleeding

Although rare, primary aorto-duodenal fistula may occur due to an infected aortic aneurysm, when erosion of the vessel affects the third portion of the duodenum. Erosion and rupture of a MAA into a gastrointestinal structure, such as the esophagus or appendix, have also been described.

7. Intraabdominal abscess

8. Hemoptysis, dysphagia, and hoarseness

Rupture of a mycotic thoracic aortic aneurysm or pseudoaneurysm, or aortobronchial fistula formation may lead to hemoptysis [33].

9. Heart failure

10. Compression

Constriction or displacement of nearby structures may be present due to MAAs.

#### **7. Infected versus inflammatory AAA**

Although inflammation is frequently associated with aortic aneurysms, the classical appearance of an AAA needs to be differentiated from aortic aneurysms that are infected. Also mycotic aneurysms need to be addressed and distinguished from a clinical entity known as "inflammatory aneurysms."

Approximately 3–10% of abdominal aortic aneurysms are characterized by increased inflammation surrounding the aneurysm. These inflammatory abdominal aortic aneurysms (IAAA) are typically differentiated from common AAAs by certain features. These include a classical description of periaortic inflammation as a white gleaming fibrotic surface with a thickened aneurysmal wall [34].

**53**

chronic aortitis.

*Mycotic Aortic Aneurysms*

cultures are negative).

**8. Diagnosis**

*DOI: http://dx.doi.org/10.5772/intechopen.86328*

Other common features of IAAAs include major adhesions and fibrosis of close anatomical structures, such as the duodenum and ureters. This fibrosis commonly

The classic triad of IAAAs includes abdominal pain, weight loss, and elevation of inflammatory markers (CRP, ESR). Inflammatory aortic aneurysms are not associated with periaortic air or fluid and are not infected (tissue samples and blood

The diagnosis of mycotic aortic aneurysms might be very challenging. In the presence of fever, general malaise, and a pulsatile abdominal mass or aortic aneurysm in imaging testing, a MAA should be suspected and investigated. An early diagnosis of MAAs is essential as it is associated with a high rate of hemorrhage due to rupture and high rate of early sepsis and mortality. Once a MAA is suspected, the

Various definitions have been proposed for the diagnosis of mycotic aneurysms,

Most series agree that the definition of mycotic aortic aneurysm should include

• Abnormal laboratory findings (elevated white cell count: WBC, C-reactive pro-

• Specific radiologic findings, including: periaortic soft tissue air, fluid, or mass,

Although blood cultures may be negative in around 25–50% of patients, negative blood cultures alone are not enough to rule out infected aneurysms, and diagnostic

Ultrasound scanning may be useful in diagnosing the presence of an aortic aneurysm, but it is not reliable for specific diagnosis of aortic infection. Digital subtraction angiography (DSA), besides being an invasive procedure, is not reliable for specific identification of features that suggest and diagnose an infected aneurysm. Imaging studies for detection of MAAs include computed tomography scan (CT) and multislice CT angiography with 3D reconstruction, as well as magnetic resonance imaging (MRI). For many groups, MRI with gadolinium enhancement is becoming the noninvasive imaging modality of choice for the diagnosis of acute or

Nuclear medicine studies, including fluorodeoxyglucose-positron emission tomography (FDG-PET) and nuclear gallium scanning, are alternative modalities

Some groups have used specific definitions to delineate mycotic aortic aneurysms, including all of the following: fever or sepsis, abnormal laboratory findings (elevated CRP or white cell count), positive blood cultures, and radiologic studies showing a false aneurysm (with or without stranding), periaortic fluid, or air around the aorta [35]. Common radiologic (CT and MRI) features of MAAs are an irregular aortic wall, a lobulated vascular periaortic mass, and peri-aneurysmal gas/

patient should be investigated with laboratory testing and imaging studies.

including clinical, laboratory and radiological features.

tein: CRP, or erythrocyte sedimentation rate: ESR).

saccular/multilobular aneurysm or pseudoaneurysm.

at least two of the following criteria:

soft-tissue mass/edema.

testing should be completed.

• Fever, sepsis, or localized pain.

• Positive blood or aortic tissue cultures.

leads to indistinct retroperitoneal tissue planes on imaging studies.

#### *Mycotic Aortic Aneurysms DOI: http://dx.doi.org/10.5772/intechopen.86328*

Other common features of IAAAs include major adhesions and fibrosis of close anatomical structures, such as the duodenum and ureters. This fibrosis commonly leads to indistinct retroperitoneal tissue planes on imaging studies.

The classic triad of IAAAs includes abdominal pain, weight loss, and elevation of inflammatory markers (CRP, ESR). Inflammatory aortic aneurysms are not associated with periaortic air or fluid and are not infected (tissue samples and blood cultures are negative).
