**1.1. Diagnosis of infected aneurysms**

Risk factors for infected aneurysm include: 1) Endothelial damage caused by atherosclerosis including pre-existing aneurysm [1], 2) Antecedent infection including bacteremia, 3) Arteri‐ al injury including iatrogenic mechanisms, such as percutaneous coronary intervention [2]. When the intima is diseased, bacteria can pass through it into deep layers of the aorta and can establish infection. Infective endocarditis (IE) remains to be main cause of infected aneurysm [3], because the risk factors of IE are very similar to those of infected aneurysms, and bacteremia and septic emboli from heart are often common features of IE.

Staphylococcus species (spp) and Salmonella spp are two major bacteria causing infected aneurysm, 28 to 71 percent and 15 to 24 percent of causes, respectively [4,5]. Streptococ‐ cus pneumoniae may be the third major, re-emerging, cause of infected aneurysms [6]. The pathology of the diseased site includes acute or chronic inflammation with bacterial

infection, abscesses, and necrosis. The suprarenal abdominal aorta is most commonly in‐ volved site.

able to visualize the edematous lesion. The diffusion images can detect fluid collection, and

Infected Aneurysm and Inflammatory Aorta: Diagnosis and Management

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In summary, the important things for the diagnosis of an infected aneurysm are the high suspicion of this disease and obtaining blood cultures and enhanced CT or MR imaging.

Surgical replacement or debridement is the treatment of choice combined with antibiotic therapy [4]. The main aims of surgical procedures are removal of infected tissue and re‐ vascularization if distal perfusion is limited. Mortality rate without surgery was 85 per‐ cent with infected thoracic aneurysm and 96 percent with infected aortic aneurysm [10,11]. Figure 2 shows a gradually enlarged infective aneurysm treated on medication alone despite the control of bacteremia [12]. Among patients who underwent surgery, mortality rates were the highest for patients with infected arch aneurysms (50 %) com‐ pared with supra-renal aortic aneurysms (43%), distal descending thoracic aneurysms (33 %), proximal descending thoracic aneurysms (16 %), or infra-renal aortic aneurysms (4 %) [10,13]. Endovascular stenting is reported to be effective in some systematic reviews with low mortality [14,15]. Because the infected focus is not removed by endovascular stenting, the procedures may be palliative, and more persistent or recurrent infections are likely to occur compared to surgical procedures. However, endovascular procedures could be a secondary choice for patients who refuse surgery, those with a very high risk

The initial choice of antibiotic therapy should be based on the culture and susceptibility results. Until the results become available, the combination treatment with vancomycin and a ceftriaxone, a fluoroquinolone, or piperacillin-tazobactam is preferable targeting gram-negative Salmonella and enteric bacteria. The optimal duration of antibiotic thera‐ py is uncertain because of the lack of randomized clinical trials. In general, four to six weeks of parenteral antimicrobial therapy is performed for the treatment of infected aneurysm followed by principles of vascular graft infection or infective endocarditis of prosthesis valve. A longer duration of treatment or additional oral antibiotics may be warranted in the clinical course of persist elevation of C-reactive proteins or recurrence

In summary, the surgical replacement in combination with antibiotics is the treatment of choice, and endovascular procedures may be palliative. The management is followed by

Large vessel vasculitits such as Takayasu's arteritis and giant cell arteritis, rheumatic and HLA-B27–associated spondyloarthropathies, Behçet's syndrome, and infections such as syphilis, tuberculosis may be the cause of inflammation of aorta, and we must differ‐

principles of vascular graft infection or infective endocarditis of prosthesis valve.

gadolinium enhancement indicates the increase of inflammatory connective tissue.

**1.2. Management of infected aneurysms**

for surgery, and those with a ruptured infected aneurysm.

of fever when drug-related fever is excluded.

**2. Inflammation of aorta: "Aortits"**

**Figure 1.** Results of Pubmed search using mycotic aneurysm or infected aneurysm.

Symptoms of an infected aneurysm vary according the lesion diseased. For example, ab‐ dominal pain and diarrhea is observed if abdominal aorta is involved, painful pulsatile mass if superficial artery is involved, and chest pain if thoracic aorta is involved. An infected aneurysm involving deep arteries or aorta may cause only fever. It might be followed as fe‐ ver of unknown origin, and could be diagnosed as an infected aneurysm only after CT imag‐ ing is acquired. If the patients were with bacteremia or a persistent high fever and their etiology was not determined, the contrast-enhanced CT imaging would be the choice for searching the diseased lesion, and an asymptomatic infected aneurysm would be one of dif‐ ferential diagnoses.

The next step of diagnosing an infected aneurysm is based on blood cultures and imaging. In all suspicious patients, blood cultures should be examined. About 50-85% of patients may be positive [5,7]. If negative, however, the infected aneurysm cannot be ruled out. Contrastenhanced CT imaging identified the infected aneurysm. Findings on CT angiography of an infected aneurysm include a disruption of aortic wall calcification, soft tissue inflammation or mass around a vessel, and periaortic fluid or air collection [8,9]. These findings can differ‐ entiate from other inflammatory aortic disease. The wall of inflammatory aorta is thickened and periaortic fibrosis sometimes observed in adhesion to surrounding organs. MR imaging is another strong tools. The T2-weighted images or mixed T1/T2-weighted STIR images are able to visualize the edematous lesion. The diffusion images can detect fluid collection, and gadolinium enhancement indicates the increase of inflammatory connective tissue.

In summary, the important things for the diagnosis of an infected aneurysm are the high suspicion of this disease and obtaining blood cultures and enhanced CT or MR imaging.
