**8. Diagnosis**

*Aortic Aneurysm and Aortic Dissection*

expanding hematomas might be seen.

4.Mesenteric ischemia

5.Osteomyelitis

an infection of an aortic aneurysm.

esophagus or appendix, have also been described.

bronchial fistula formation may lead to hemoptysis [33].

8. Hemoptysis, dysphagia, and hoarseness

**7. Infected versus inflammatory AAA**

a clinical entity known as "inflammatory aneurysms."

6. Gastrointestinal bleeding

7. Intraabdominal abscess

9. Heart failure

10. Compression

rates.

3.Acute ischemia of the lower limbs

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

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

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.

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

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

Rupture of a mycotic thoracic aortic aneurysm or pseudoaneurysm, or aorto-

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

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

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].

**52**

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 patient should be investigated with laboratory testing and imaging studies.

Various definitions have been proposed for the diagnosis of mycotic aneurysms, including clinical, laboratory and radiological features.

Most series agree that the definition of mycotic aortic aneurysm should include at least two of the following criteria:


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/ soft-tissue mass/edema.

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 testing should be completed.

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 chronic aortitis.

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

#### **Figure 1.**

*CT scan showing a reconstruction of a distal infrarenal MAA (A). Fused frontal imaging of the contrast CT and FDG-PET scan showing highly elevated FDG uptake in the distal aorta (B).*


*MAA: mycotic aortic aneurysm; A.: aortic; CRP: C-reactive protein; ESR: elevated sedimentation rate; (\*): contained or not; +: positive; +++: highly positive.*

#### **Table 2.**

*Ribé's proposal of new modified classification of MAAs.*

for evaluating mycotic aortic aneurysms that are becoming increasingly useful. PET-CT testing has a very high sensitivity and both high positive and negative predictive values for aortic graft infection, and also provides important information in the diagnosis of mycotic aneurysms [35].

Current imaging studies have reported variable sensitivities regarding FDG-PET. Most series have published specificities of 88–100% for 18F-FDG PET and PET-CT for diagnosing active inflammation in arteritis (**Figure 1**) [35–37].

There are very few classifications regarding infected aortic aneurysms. The author would like to add a new modified classification of MAAs (**Table 2**).

### **9. Management of MAAs**

#### **9.1 Antibiotherapy**

#### *9.1.1 Recommendations*

Various groups recommend vancomycin plus an anti-Gram-negative antibiotic (for coverage of *Salmonella* and Gram-negative microorganisms), including

**55**

*Mycotic Aortic Aneurysms*

**9.2 Surgery**

blowout of the arterial stump.

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

intravenous fluoroquinolone, ceftriaxone, and piperacillin-tazobactam. Results of blood cultures and tissue samples are monitored for hours or days, until a pathogen is correctly identified. Empirical antimicrobial therapy is maintained during this time, and reviewed once a pathogen is defined. Antibiotherapy should then be

In general, at least 6 weeks of intravenous plus oral antibiotics should be implemented. However, there are no data to support specific duration of antibiotic therapy. Several authors have advocated long-term oral antibiotics after hospital discharge for all patients undergoing intervention, especially those who underwent endovascular repair. If positive cultures are obtained from tissue samples, life-long

The aneurysm should be dissected back to normal aortic tissue. Once the aneurysm has been resected, the proximal aorta should be oversewn with a nonabsorbable suture, ligated 1–2 cm proximally, and possible omental coverage, to prevent

In those cases where it is likely that the patient may develop acute ischemia after arterial ligation, immediate revascularization should be considered. Extraanatomical bypass (axillobifemoral bypass graft) after aneurysm resection and stump closure has been traditionally used. Autogenous vein, antibiotic, and silver impregnated grafts are also used. Other reported options are femoral-popliteal deep veins, cryopreserved arterial allografts, and Dacron prosthetic grafts [39–41].

Some groups have described this technique of retrograde visceral revascularization (1, 2, 3, or 4 visceral vessels might be revascularized), followed by TEVAR/ EVAR. The technique is performed through a midline laparotomy incision. When using the infrarenal aorta as the inflow vessel, a bifurcated 14 × 7 mm Dacron graft is prepared. Two side grafts (usually 6 mm Dacron grafts) are anastomosed to the lateral aspect of the bifurcated graft, to create the 4-graft retrograde bypass. Correct routing and fashioning of the grafts are crucial to avoid early graft thrombosis. The right branch (6–7 mm) is anastomosed to the right renal artery (RA). The right 7 mm graft would be anastomosed side-to-end to the coeliac axis (tunneled in a retropancreatic position). To avoid graft kinking, the left 7 mm graft is anastomosed in an end-to-side fashion to the SMA in a "lazy C" configuration [42].

Endovascular repair may be a suitable option for infected aortic aneurysms in high-risk patients, when open surgery mortality would be prohibitive. In cases of ruptured MAAs, endovascular repair may be an appropriate alternative, as a definitive treatment or until debridement and a final treatment may be performed. There is still ongoing controversy in the literature regarding the endovascular option as a main

tailored to cultures and antimicrobial susceptibility [23, 24, 31].

antibiotic therapy should be considered [31, 32, 38, 39].

*9.2.1 Excision and ligation without arterial reconstruction*

*9.2.2 Excision with immediate revascularization*

*9.2.3 Excision with interval reconstruction*

therapy or as an alternative [23, 30, 34, 39, 43].

*9.2.3.1 Hybrid repair*

**9.3 Endovascular**

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

intravenous fluoroquinolone, ceftriaxone, and piperacillin-tazobactam. Results of blood cultures and tissue samples are monitored for hours or days, until a pathogen is correctly identified. Empirical antimicrobial therapy is maintained during this time, and reviewed once a pathogen is defined. Antibiotherapy should then be tailored to cultures and antimicrobial susceptibility [23, 24, 31].

In general, at least 6 weeks of intravenous plus oral antibiotics should be implemented. However, there are no data to support specific duration of antibiotic therapy. Several authors have advocated long-term oral antibiotics after hospital discharge for all patients undergoing intervention, especially those who underwent endovascular repair. If positive cultures are obtained from tissue samples, life-long antibiotic therapy should be considered [31, 32, 38, 39].

#### **9.2 Surgery**

*Aortic Aneurysm and Aortic Dissection*

Radiologic findings 1.A. ulcer or

*or not; +: positive; +++: highly positive.*

Inflammatory markers (CRP and

ESR)

**Figure 1.**

**Table 2.**

2.A. mass or 3.A. pseudoaneurysm

*and FDG-PET scan showing highly elevated FDG uptake in the distal aorta (B).*

for evaluating mycotic aortic aneurysms that are becoming increasingly useful. PET-CT testing has a very high sensitivity and both high positive and negative predictive values for aortic graft infection, and also provides important information

Aortic tissue — +/− + + Incidence Rare Very rare Very rare Very rare Bacteriology Absent Present Present Present *MAA: mycotic aortic aneurysm; A.: aortic; CRP: C-reactive protein; ESR: elevated sedimentation rate; (\*): contained* 

**MAA grade I MAA grade II MAA grade III MAA grade IV**

Grade I and periaortic gas Grade I and rupture (\*)

Grade I and periaortic edema

*CT scan showing a reconstruction of a distal infrarenal MAA (A). Fused frontal imaging of the contrast CT* 

+ + +++ +++

Current imaging studies have reported variable sensitivities regarding FDG-PET. Most series have published specificities of 88–100% for 18F-FDG PET and PET-CT for diagnosing active inflammation in arteritis (**Figure 1**) [35–37].

There are very few classifications regarding infected aortic aneurysms. The

Various groups recommend vancomycin plus an anti-Gram-negative antibiotic (for coverage of *Salmonella* and Gram-negative microorganisms), including

author would like to add a new modified classification of MAAs (**Table 2**).

in the diagnosis of mycotic aneurysms [35].

*Ribé's proposal of new modified classification of MAAs.*

**9. Management of MAAs**

**9.1 Antibiotherapy**

*9.1.1 Recommendations*

**54**

#### *9.2.1 Excision and ligation without arterial reconstruction*

The aneurysm should be dissected back to normal aortic tissue. Once the aneurysm has been resected, the proximal aorta should be oversewn with a nonabsorbable suture, ligated 1–2 cm proximally, and possible omental coverage, to prevent blowout of the arterial stump.

#### *9.2.2 Excision with immediate revascularization*

In those cases where it is likely that the patient may develop acute ischemia after arterial ligation, immediate revascularization should be considered. Extraanatomical bypass (axillobifemoral bypass graft) after aneurysm resection and stump closure has been traditionally used. Autogenous vein, antibiotic, and silver impregnated grafts are also used. Other reported options are femoral-popliteal deep veins, cryopreserved arterial allografts, and Dacron prosthetic grafts [39–41].

#### *9.2.3 Excision with interval reconstruction*

#### *9.2.3.1 Hybrid repair*

Some groups have described this technique of retrograde visceral revascularization (1, 2, 3, or 4 visceral vessels might be revascularized), followed by TEVAR/ EVAR. The technique is performed through a midline laparotomy incision. When using the infrarenal aorta as the inflow vessel, a bifurcated 14 × 7 mm Dacron graft is prepared. Two side grafts (usually 6 mm Dacron grafts) are anastomosed to the lateral aspect of the bifurcated graft, to create the 4-graft retrograde bypass. Correct routing and fashioning of the grafts are crucial to avoid early graft thrombosis. The right branch (6–7 mm) is anastomosed to the right renal artery (RA). The right 7 mm graft would be anastomosed side-to-end to the coeliac axis (tunneled in a retropancreatic position). To avoid graft kinking, the left 7 mm graft is anastomosed in an end-to-side fashion to the SMA in a "lazy C" configuration [42].

#### **9.3 Endovascular**

Endovascular repair may be a suitable option for infected aortic aneurysms in high-risk patients, when open surgery mortality would be prohibitive. In cases of ruptured MAAs, endovascular repair may be an appropriate alternative, as a definitive treatment or until debridement and a final treatment may be performed. There is still ongoing controversy in the literature regarding the endovascular option as a main therapy or as an alternative [23, 30, 34, 39, 43].

Procedures are usually performed under epidural or general anesthesia, with open exposure of one or both common femoral arteries. In those undergoing TEVAR, cerebrospinal fluid (CSF) drainage should be considered in those patients with expected long thoracic segment coverage. Coverage of the left subclavian artery (LSA) is usually avoided unless completely necessary. Some authors have described aneurysm sac drainage after EVAR. The procedure is usually performed in a prone position. A 21-G needle is inserted into the aneurysm sac. Following dilation, a 14–16 Fr drainage catheter is used to aspirate and send the contents for microbiological analysis. Pryluck et al. consider that it might aid to decrease the infectious content of the aneurysm sac and effectively prevent late reinfection [44].

## **10. Prosthetic aortic infection**

Although this chapter tries to focus on primary MAAs, infected aneurysms or pseudoaneurysms can also occur following prosthetic replacement of the aorta.

The incidence of prosthetic aortic graft infection has been described in 0.5–2% of cases, including both early and delayed-onset complications [45]. All these prosthetic graft infections are associated with high morbidity and mortality rates. As previously described in the chapter, different surgical techniques have been described for repair of infected MAAs and aortic graft infection. Removal of all infected tissue and infected grafts are essential for a successful result.

Plastic surgery-reassembling procedures have also been described for coverage of arterial tissue after reconstruction, especially after infections involving the ascending aorta, aortic arch, and descending thoracic aorta. These procedures involve musculocutaneous pedicled flaps using various different muscles (including rectus abdominis, pectoralis major, latissimus dorsi, and vastus lateralis muscles) [46]. The application of these vascularized muscle and omental flaps by plastic surgeons, in conjunction with cardiothoracic and vascular surgeons, might be an important alternative for an adequate management of these prosthetic aortic infections. Omental flaps have been previously described as the most common applied type of autologous flap for coverage of ascending aorta, aortic arch, and descending thoracic aortic graft infections. Other options for wound closure in cases of infected prosthetic aortic grafts with associated wound infection include different types of vacuum-assisted closure (VAC) devices [46].
