Computed tomography and ultrasound diagnosis of mycotic aneurysm of the abdominal aorta due to Salmonella

Non-aneurysmal infectious aortitis: a case report

Infectious aortitis is a rare clinical entity that is most often associated with an abdominal aortic aneurysm. There have been very few documented cases of aortitis in the setting of a normal-sized caliber aorta. We present a 67-year-old patient who presented to our Emergency Department with a history of recent fevers, fatigue, and abdominal pain. Based on an abdominal computed tomography scan, the patient was initially thought to have ruptured an abdominal aortic aneurysm of infectious etiology with extension into the left psoas muscle. Explorative laparotomy, however, revealed an infected abdominal aorta secondary to a retroperitoneal abscess with no evidence of aneurysm or pseudoaneurysm. The pathophysiology of the disease suggests that infectious aortitis and mycotic aneurysm represent extremes along a spectrum of the same disease. Establishing a diagnosis of aortic infection before the formation of an aneurysm or rupture is very difficult, but essential in preventing the devastating complications.

Infected Aortic Aneurysms: Imaging Findings

PURPOSE

To determine the imaging characteristics of infected aortic aneurysms.

MATERIALS AND METHODS

Review of records of patients with surgical and/or microbiologic proof of infected aortic aneurysm obtained over a 25-year period revealed 31 aneurysms in 29 patients. This study included 21 men and eight women (mean age, 70 years). One radiologist reviewed 28 computed tomographic (CT) studies (22 patients underwent CT once and three patients underwent CT twice), 12 arteriograms (12 patients underwent arteriography once), eight nuclear medicine studies (six patients underwent nuclear medicine imaging once and one patient underwent nuclear medicine imaging twice), and three magnetic resonance (MR) studies (three patients underwent MR imaging once). Features evaluated included aneurysm size, shape, and location; branch involvement; aortic wall calcification; gas; radiotracer uptake on nuclear medicine studies; and periaortic and associated findings. The location of infected aortic aneurysms was compared with that of arteriosclerotic aneurysms.

RESULTS

Aneurysms were located in the ascending aorta (n = 2, 6%), descending thoracic aorta (n = 7, 23%), thoracoabdominal aorta (n = 6, 19%), paravisceral aorta (n = 2, 6%), juxtarenal aorta (n = 3, 10%), infrarenal aorta (n = 10, 32%), and renal artery (n = 1, 3%). Two patients had two infected aortic aneurysms. CT revealed 25 saccular (93%) and two fusiform (7%) aneurysms with a mean diameter at initial discovery of 5.4 cm (range, 1-11 cm). Paraaortic soft-tissue mass, stranding, and/or fluid was present in 13 (48%) of 27 aneurysms, and early periaortic edema with rapid aneurysm progression and development was present in three (100%) patients with sequential studies. Other findings included adjacent vertebral body destruction with psoas muscle abscess (n = 1, 4%), kidney infarct (n = 1, 4%), absence of calcification in the aortic wall (n = 2, 7%), and periaortic gas (n = 2, 7%). Angiography showed 13 saccular aneurysms with lobulated contour in 10 (77%). Nuclear medicine imaging showed increased activity consistent with infection in six (86%) of seven aneurysms. MR imaging showed three saccular aneurysms. Adjacent abnormal vertebral body marrow signal intensity was seen in one (33%) of three patients.

CONCLUSION

Saccular aneurysms (especially those with lobulated contour) with rapid expansion or development and adjacent mass, stranding, and/or fluid in an unusual location are highly suspicious for an infected aneurysm.

Comparison of the clinical and laboratory features of muscle infections caused by Salmonella and those caused by other pathogens

Muscle infections caused by Salmonella constitute an uncommon complication of extraenteric salmonellosis. The aim of this study was to compare the clinical features of Salmonella muscle infections with those reported in several large series of typical, both tropical and non-tropical, pyomyositis, caused mostly by Staphylococcus aureus. A literature survey of Salmonella muscle infections was carried out by using MEDLINE files 1966 through 2000, and cross-references from the selected articles, as well as major reviews of Salmonella infections and of pyomyositis. The survey yielded 32 cases suitable for analysis. The sex distribution, duration of symptom at presentation, degree of fever, involvement of multiple muscle groups, and leukocyte counts were not significantly different between patients with muscle infections caused by Salmonella and typical pyomyositis patients. In contrast, the median age of the patients with Salmonella muscle infections, and the rate of underlying conditions, were significantly higher than those in typical pyomyositis. Psoas muscle was involved more commonly in Salmonella infections than in typical pyomyositis, and the yield of positive blood cultures and, particularly, the mortality rate, were substantially higher in Salmonella muscle infections than in typical pyomyositis. We conclude that patients with Salmonella muscle infections seem to have some different characteristics with respect to typical pyomyositis, such as older age, and higher rates of associated conditions, psoas muscle involvement, bacteremia, and mortality.

Ruptured abdominal aorta secondary to psoas muscle abscess due to Klebsiella pneumoniae in an alcoholic

An alcoholic patient with low back pain and Klebsiella pneumoniae septicaemia is reported. Computed tomography revealed abdominal aortic rupture associated with a psoas abscess. Aortic ligation above and below the rupture site and an axillo-femoral bypass were performed, but the patient died on the first postoperative day. Alcoholism is a common underlying disease in K. pneumoniae septicaemia and its septic metastasis to the psoas muscle. The prognosis of aortic infection secondary to psoas abscess is very poor once aortic rupture occurs. Prompt abscess drainage following correct diagnosis and arterial reconstruction before aortic rupture are mandatory.

Mycotic pseudoaneurysm of the descending thoracic aorta associated with vertebral osteomyelitis

A patient with osteomyelitis of the lower thoracic spine is reported in whom computed tomography (CT) revealed a large false aneurysm of the descending aorta. Useful radiological signs of the diagnosis are described, namely a thin aneurysm wall, a multilobulated margin and deformity of the aneurysm by adjacent vascular and osseous structures. Mycotic aneurysms of the aorta have a high mortality and the CT demonstration of a pseudoaneurysm has a vital role in management.

Rupture of a non-aneurysmal salmonella infected aorta

A 65-year-old man with salmonella bacteraemia developed a retroperitoneal collection as a result of infection and subsequent rupture of the abdominal aorta. Computed tomography (CT) showed the collection but there was no aneurysm on CT or at surgery. The main diagnostic feature of salmonella aortitis is the presence of an aneurysm; this report indicates that a non-aneurysmal infected aorta can rupture. The importance of considering a ruptured aorta as the cause of retroperitoneal collections is emphasised, even when the aorta is of normal calibre.