The mycotic aortic aneurysm is a rare disease with an incidence of about 0.65% to 2% of all aortic aneurysms [1].

Pathogens include infectious organisms, the most common of which are Staphylococcus aureus, Salmonella and Streptococcus [2].

We report the case of a patient with a saccular aneurysm of the infra-renal aorta, due to a systemic infection with Salmonella Paratyphi B treated successfully with antibiotics and surgical resection.

We report the case of a 65 year old man (a farmer), diabetic, admitted to the emergency department for fever and severe abdominal pain which started since 10 days. Biological tests have revealed leukocytosis 22,000/mm³, and blood cultures were positive for Salmonella paratyphi B.

The transthoracic echocardiography excluded endocarditis Abdominal CT scan revealed a small aneurysm of the antero-lateral wall of the aorta measuring 15 mm in diameter (Figure 1).

Figure 1: Initial computed tomography scan showing a saccular aneurysm of the abdominal aorta (arrow).

Antibiotic therapy was started with ceftriaxone (1.0 g every 12 h), and ofloxacin (400 mg every 12 h) for 6 weeks. The evolution was marked by the resolution of fever, abdominal pain, and bacteremia.

An abdominal CT scan performed after antibiotic therapy has revealed the progression and expansion of the aneurysm to 20 mm (Figure 2).

Figure 2: Second CT scan showing enlargement of the aneurysmal dilation (arrow).

Because of the high risk of aneurysmal rupture, the patient underwent open surgery through a median laparotomy.

The intraoperative exploration revealed an inflammation and a saccular dilatation of the infra-renal aorta (Figure 3).

Figure 3: Intraoperative view showing the saccular dilatation of the infra-renal aorta (arrow).

The aorta and the common iliac arteries were clamped and the aorta was opened. The aortic wall was atherosclerotic.

After resection of the aneurysm with debridement of the surrounding tissue, an anatomical reconstruction, with replacement of the damaged portion of the aorta with a synthetic graft, with implantation of the lower mesenteric artery into the prosthesis was performed (Figure 4).

Figure 4: Intraoperative view showing completed anatomical repair.

Histopathological exam and cultures of a sample of the aortic wall were negative.

The postoperative course was uneventful. The patient had no abdominal pain, and the pulses of the two lower limbs were present.

The patient was discharged after 7 days.

He was seen at 1 month after the operation and he is fine.

Mycotic aortic aneurysms can occur following a bacterial infection of a previously normal artery wall or secondary infection of a preexisting aneurysm [3].

Staphylococcus aureus and Salmonella typhi are the main microorganisms involved in the occurrence of mycotic aneurysms, especially in elderly diabetic patients, as was the case of our patient [4,5].

As a result of bacteremia, atheromatous lesions within the aneurysm can become infected, leading to necrosis and rupture of the aortic wall [6].

Most patients have non-specific symptoms like fever, back pain, and abdominal pain.

The biological manifestations are bacteremia, hyper leukocytosis, and elevated erythrocyte sedimentation rate [5]. A positive blood culture with radiological abnormalities of the aorta strongly suggests a bacterial disease [7].

The intensive antibiotic therapy is crucial and should be started as early as possible before surgery. The time required varies from 6 to 8 weeks [8].

Surgical treatment of mycotic aneurysms includes a resection of the aneurysmal sac with debridement of the infected tissue. The reconstruction can be extra-anatomic to avoid the use of grafts in a contaminated area [5,9]. However, the patency rate for axillo-femoral bypass is poor [10].

The anatomic aortic reconstruction using cryopreserved homograft or grafts showed excellent short and long-term results [11,12]. The advantage of homograft is to prevent recurrence of the infection, but they raise the problem of availability.

In our case, inflammation of surrounding tissue was important, but without local signs of infection, and for the unavailability of homograft, we used an anatomical reconstruction with a prosthetic Dacron graft impregnated with rifampicin. An implantation of the lower mesenteric artery in the prosthesis was performed.

The postoperative mortality rate of this type of aneurysm remains high, between 21% and 36% [13].

Experience with endovascular treatment of mycotic aneurysms is limited [14]. Therefore, it is still uncertain whether endovascular treatment or surgical prosthetic repair provides the best short and long-term results.

The main disadvantage of the endovascular treatment is that the infected tissue is not resected, which can facilitate the recurrence of the infection, and the infection of the stent graft [15].

Mycotic aneurysms of the aorta remain a severe life-threatening disease. The management is based on the resection of infected tissues, and vascular reconstruction using allografts; if they are unavailable by prosthetic graft, associated with an antibiotic therapy for a long period.