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Salmonella Aortic Aneurysm: Suggestions for Diagnosis and Therapy Based on Personal Experience: A Case Report

Posted on: Sunday, 5 December 2004, 03:00 CST

Infectious aneurysm is a rare event, especially after the introduction of antibiotic therapy. However, its early detection is very important for timely treatment with antibiotics and surgical intervention. This pathology may generally be due to mycotic endocarditis or septic embolization, prevailing in the preantibiotic era, and to aortitis, whose incidence is actually increasing, mainly in subjects with preexisting large-vessel atherosclerosis and intimal defects. This clinical entity is usually defined as microbial arteritis and recognizes Salmonella spp as the microorganism most frequently isolated from blood or vascular tissue cultures. The authors present the case of a 56-year-old man with a history of hypertension that some weeks before admission manifested as hyperpyrexia and episodic lumbar pain, associated with hepatosplenomegaly and with a pulsing mass in the periumbilical region. Abdominal computed tomography (CT) scan documented a voluminous infrarenal aortic aneurysm with a markedly reduced and irregular vessel wall. The patient underwent surgical excision of the aneurysm, during which marked periaortic inflammation phenomena, complete absence of the posterior aortic wall for a length of 5-6 cm, and the exposure of the correspondent vertebral bodies were observed. Histopathologic examination of the aneurysmal tissue showed atheromatous and thrombotic aspects and confirmed strong signs of inflammation. This case may suggest that the occurrence of microbial aortitis, especially from Salmonella spp, should be taken into account in the presence of a septic status associated with back, abdominal, or thoracic pain.

Introduction

Infected aneurysm is a pathology seldom encountered, although it has been known since the nineteenth century. Sir William Osier,1 in 1885, was the first to describe it in pathophysiological terms, underlining how the endocarditic vegetations detached septic emboli that, implanting themselves in the large vessel wall, produced an aneurysmal dilation.

The endocarditic etiology,2 prevailing in the preantibiotic era, is now declining. On the contrary, the cases of aneurysms due to aortitis, especially caused by Salmonella, in subjects with preexisting large-vessel atherosclerosis are increasing.3 This clinical entity is usually termed microbial arteritis,4 indicating the colonization of the vessel intima, already altered (eg, atherosclerosis), by the microorganism. From an anatomopathologic point of view, it presents as an aspecific inflammation with edema, leukocyte infiltration, and fibrin precipitation (endoarteritis); it may also spread to perivascular tissues, creating stenosis or dilation of the artery until it ruptures, with a usually tumultuous evolution.5

Case Report

A male patient, 56 years old, abstemious, a good eater, overweight, with a clinical history of hypertension and anxious- depressive syndrome, who for a few weeks had presented hyperpyrexia, asthenia, anorexia, drowsiness, nocturnal perspiration, shivers, and episodic lumbar pain, was admitted to the Department of Internal Medicine. Moreover, before the fever appeared, the patient had episodic diarrhea, which lasted for a few days. At the clinical examination, splenomegaly with moderate hepatomegaly and a pulsing mass in the periumbilical region were found.

An abdominal ultrasound scan showed a marked dilatation of the abdominal aorta for a length of about 8 cm and a maximum diameter of 6.5 cm. On the basis of this finding a contrastenhanced CT scan (Figures 1-3) was performed and confirmed the presence of a voluminous infrarenal aortic dilatation (10 cm diameter; 5 cm length) that extended as far as the bifurcation; the iliac arteries were uninvolved. The dilatation extended mainly posteriorly and to the right, and the vessel wall was markedly reduced.

Three of 4 blood cultures were positive for Salmonella spp, and preoperative antibiotic therapy with ceftriaxone was thus initiated. On the basis of the computed tomography (CT) scans, 4 days after the start of antibiotic treatment, the patient underwent emergency surgery, during which marked periaortic inflammation phenomena, complete absence of posterior aortic wall for a length of 5-6 cm, and the exposure of the correspondent vertebral bodies were observed. The operation included suturing of the infrarenal aortic stump and of the iliac arteries, excision of the pseudoaneurysmal thrombus, curettage of the inflamed periaortic tissue, and creation of an axillobifemoral prosthetic bypass.

Figure 1. Contrast-enhanced computed tomography scan of the abdomen showing an aorta without dilatation at the level of the renal hilum. The aorta above the renal arteries and the renal vessels were normal.

Figure 2. At the level of the infrarenal aortic artery a voluminous and irregular dilatation is clearly visible (10 cm diameter; 5 cm length), whose wall thickness is greatly reduced with an anterior prominence and indentation.

Figure 3. In this image, near the previous scan, a similar extended dilatation of the aneurysm can be seen, manly posteriorly and to the right, so that the vessel wall is practically no longer visible.

Histologic examination of the aortic wall (Figure 4) presented atheromatous aspects, developing thrombosis, and marked inflammation; Staphylococcus lugdunensis was also isolated from the vessel wall, considered meaningless with respect to the etiopathogenesis of the disease. After the immediate postoperative period, the patient was moved to the Department of Infectious Diseases, where antibiotic therapy with IV ampicillin was initiated. After the operation, and for the rest of his stay in the department, the patient remained apyretic. Following 2 stool cultures negative for Salmonella, the patient was discharged 17 days after the operation. The Salmonella microorganism was typed as Salmonella cholerae-suis.

Discussion

The etiopathogenesis of mycotic aneurysms may include 6 different mechanisms6: (1) septic embolization lodged in the vasa vasorum or vessel lumen, (2) a contiguous inflammatory process outside the vessel wall that extends to a nearby artery, (3) inoculation of bacteria at the time of accidental arterial trauma, (4) self- induced vascular manipulation, (5) iatrogenic causes, (6) an intimai defect, such as an atherosclerotic plaque, that is seeded by concurrent bacteremia.

Apart from Salmonella spp, the microorganisms most frequently isolated from blood or vascular tissue cultures are Staphylococcus aureus, Escherichia coli, Bacteroides fragilis, and Streptococcus pneumoniae.7,8

Eight percent of salmonellosis present a bacteremia9; endothelial infection of arteries (endothelitis) is more often observed among patients over 50 years of age (25%),10 because Salmonella has a particular tropism for arterial walls altered by atherosclerosis. Healthy intima, instead, is ordinarily highly resistant to bacterial encroachment and thus rarely infected.11,12

The distinguishing features of Salmonella cholerae-suis infection are the rarity of enteric disease but the high frequency of septicemia, metastatic manifestations, and repeated bouts of clinical disease due to survival of the microorganism outside the intestinal tract for several years.11,13 In addition, Salmonella cholerae-suis is 1 of the few nontyphi Salmonella species that have virulence plasmids, highly associated with invasive infection.14

The infected aneurysm is characterized by the nonspecificity of the signs and symptoms at presentation; this renders it a highly insidious pathology that may rapidly evolve toward rupture of the vessel.

Pain is less frequent in thoracic infections (17%) than in abdominal (44%), and back (46%) pain in abdominal infections.15

Fever is almost always present and is the common symptom for localization of the aneurysm. The guidelines for diagnosis will thus be the finding of a throbbing mass together with the presence (in a febrile patient) of blood cultures positive for Salmonella.

A computed tomography scan with contrast enhancement is considered the method of choice for the diagnosis of mycotic aneurysms. Suggestive radiologie signs are the following: the irregular and thicker peripheral enhancement rim of the vessel, consistent with periaortic inflammation; periarterial collections or adjacent vertebral osteomyelitis; and loss of intimai calcifications in the involved aortic tract. Arteriography may be performed afterward in order to plan the surgical procedure.16,17

Figure 4. Histologie aspects of the abdominal aortic wall in the aneurysm site: A. Vessel intima is heavily infiltrated by leukocytes, and diffuse hemorrhage can be observed (hematoxylin eosin 75). B. Leukocyte infiltration extends also to the muscular tunic, which appears deeply fragmented (arrows) (Van Gieson 75). C. Adventitia is also infiltrated, and great parts of the vasa vasorum are involved and appear thrombotic (arrows) (hematoxylin eosin 75). D. The picture shows phenomena of intimal disjunction from the muscular tunic, which appears intensely edematous (Van Gieson 150). E. Edema and infiltration surround and dissect the muscular fibers; a breach in the muscular tunic is visible on the right side of the picture; in the background are many thrombotic vessels (arrows) (Van Gieson 75).

The treatment of mycotic aneurysm includes 3 fundamental st\eps: prolonged antibiotic therapy, curettage of the infected region, and revascularization.11,18,19 Broad-spectrum bactericidal antibiotic therapy should be quickly initiated and subsequently adjusted on the basis of susceptibility data15; according to the literature, maintaining it for as long as possible would guarantee higher survival probabilities. Ceftriaxone, ciprofloxacin, and ampicillin are usually the most efficacious drugs for this pathology; nevertheless, Salmonella species resistant to cotrimoxazol, chloramphenicol, and ampicillin are now on the increase.20 In extraintestinal infections due to Salmonella it is therefore better to use more recent antibiotics, like third-generation cephalosporins or new quinolones.21

Medical therapy alone has a 100% mortality rate; surgical treatment is therefore fundamental.11,15 Surgical therapy consists of the excision of the affected tract of aortic wall with wide debridement of surrounding infected tissues, followed by revascularization. This may be done in 2 ways: in situ,19 which requires positioning of a synthetic prosthesis in an infected site, with the risk of a rare but severe prosthesis infection; and extra- anatomical bypass, which may generate thrombotic complications, consequently necessitating further reoperations. This approach, usually performed through an axillobifemoral graft,22 is associated with the least postoperative complications and with the best survival rate: about 71%, according to the literature, compared with 51% of in situ revascularization.23

In conclusion, a patient over 50 years old, presenting with fever, and back, or abdominal, or thoracic pain and with blood cultures positive for Salmonella, should always generate a suspicion of Salmonella aortitis with possible formation of an infected aneurysm,

While the mortality rate remains high, early diagnosis, timely antibiotic therapy, and adequate surgical treatment represent the tools that can improve the survival and prognosis of affected patients.

REFERENCES

1. Osier W: The Gulstonian lectures on malignant endocarditis. Br Med J 1:467-470, 1885.

2. Brown SL, Busuttil RW, Baker JD, et al: Bacteriologic and surgical determinants of survival in patients with mycotic aneurysms. J Vase Surg 1:541-547, 1984.

3. Sower ND, Whelan TJ Jr: Suppurative arteritis due to Salmonella. Surgery 52:851-859, 1962.

4. Oskoui R, Davis WA, Gomes MN: Salmonella aortitis: A report of a successfully treated case with a comprehensive review of the literature. Arch Intern Med 153:517-525, 1993.

5. Robbins SL, Cotran RS, Kumar V: Vasi sanguigni. In: Le Basi Patologiche delle Malattie, ed. 3. Padova: Piccin Nuova Libraria SpA, 1987, p 654.

6. Johansen K, Devin J: Mycotic aortic aneurysms: A reappraisal. Arch Surg 118:583-588, 1983.

7. Suddleson EA, Catz SG, Kohl RD: Mycotic suprarenal aortic aneurysm. Ann Vase Surg 91:263-269, 1987.

8. Wilson SE, Gordon E, Van Wagenen PB: Salmonella arteritis. Arch Surg 112:415-419, 1997.

9. Blaser MJ, Feldman RA: Salmonella bacteremia: Report to the Centers for Disease Control, 1968-1979. J Infect Dis 143:743-746, 1981.

10. Cohen SS, O'Brien TF, Schoenbaum S, et al: The risk of endothelial infection in adults with Salmonella bacteremia. Ann Intern Med 89:931-932, 1978.

11. Jao-Hsien Wang, Yung-Ching Liu, et al: Mycotic aneurysm due to non-typhi Salmonella: Report of 16 cases. Clin Infect Dis 23:743- 747, 1996.

12. Oz MC, McNicholas KW, Serra AJS, et al: Review of Salmonella mycotic aneurysms of the thoracic aorta. J Cardiovasc Surg 30:99- 103, 1989.

13. Allison MJ, Dalton HP, Escobar MR, et al: Salmonella cholerae- suis infections in man: A report of 19 cases and a critical literature review. South Med J 62:593-596, 1969.

14. Kawahara K, Haraguchi Y, Tsuchimoto M, et al: Evidence of correlation between 50-kilobase plasmid of Salmonella cholerae-suis and its virulence. Microb Pathog 4:155-163, 1988.

15. Soravia-Dunand VA, Loo VG, Salit IE: Aortitis due to Salmonella: Report of 10 cases and comprehensive review of the literature. CHn Infect Dis 29:862-868, 1999.

16. Gomes MN, Choyke PL: Infected aortic aneurysms: CT diagnosis. J Cardiovasc Surg 33:684-689, 1992.

17. Gonda RL, Gutierrez OH, Azodo MVU: Mycotic aneurysms of the aorta: Radiologie features. Radiology 168:343-346, 1988.

18. Meerkin D, Yinnon AM, Munter RG, et al: Salmonella mycotic aneurysm of the aortic arch. CHn Infect Dis 110:557-559, 1995.

19. Ting AC, Cheng SV: Repair of Salmonella mycotic aneurysm of the paravisceral abdominal aorta using in-situ prosthetic graft. J Cardiovasc Surg 38:665668, 1997.

20. Lee LA, Puhr ND, Maloney EK, et al: Increase in antimicrobial- resistant Salmonella infections in the United States, 1989-1990. J Infect Dis 170:128-134, 1994.

21. Soe GB, Overturf GD: Treatment of typhoid fever and other systemic salmonelloses with cefotaxime, ceftriaxone, cefoperazone, and other newer cephalosporins. Rev Infect Dis 9:719-736, 1987.

22. Taylor LM, Deitz DM, McConnell DB, et al: Treatment of infected abdominal aneurysms by extraanatomic bypass, aneurysm excision and drainage. Am J Surg 155:655-658, 1988.

23. Pasic M, Carrel T, Tonz P, et al: Mycotic aneurysm of the abdominal aorta: Extra-anatomic versus in situ reconstruction. Cardiovasc Surg 1:48-52, 1993.

Valerio Cicconi, MD,* Stefano Mannino, MD,[dagger] Giuseppe Caminiti, MD,* Lucio Cuoco, MD,* Antonio Gasbarrini, MD,* Fabio Vecchio, MD,[double dagger] Francesco Snider, MD, Nicol Silveri Gentiloni, MD,* and Giovanni Gasbarrini, MD,* Rome, Italy

Angiology 55:701-705, 2004

From the Departments of * Internal Medicine, [dagger] Neurosurgery, Cardiovascular Surgery, and [double dagger] Pathology, Catholic University of the Sacred Heart, Rome, Italy

Correspondence: Valerio Cicconi, MD, Department of Internal Medicine, Catholic University School of Medicine, L.go Gemelli, 8, 00168 Rome, Italy

E-mail: angiologia@rm.unicatt.it

2004 Westminster Publications, Inc., 708 Glen Cove Avenue, Glen Head, NY 11545, USA

Copyright Westminster Publications, Inc. Nov/Dec 2004

Source: Angiology

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