AJR:185, August 2005 463 AJR 2005; 185:463–465 0361–803X/05/1852–463 © American Roentgen Ray Society Yang et al. Mycotic Aortic Aneurysm Vascular Imaging • Case Report Mycotic Aortic Aneurysm Presenting Initially as an Aortic Intramural Air Pocket Chung-Yi Yang 1 Kao-Lang Liu Chung-Wei Lee Yuk-Ming Tsang Shyh-Jye Chen Yang C-Y, Liu K-L, Lee C-W, Tsang Y-M, Chen S-J Received July 22, 2004; accepted after revision September 15, 2004. 1 All authors: Department of Medical Imaging, National Taiwan University Hospital, College of Medicine, National Taiwan University, No. 7, Chung San S. Rd., Taipei 100, Taiwan, ROC. Address correspondence to K.-L. Liu (wgl@ntumc.org). ycotic aortic aneurysm is a com- mon complication of the hematog- enous spread of bacterial infection [1]. Early detection of a mycotic aortic aneurysm is essential for a rapid and ef- ficacious initial treatment and, therefore, for an improved prognosis. This case shows that an intraaortic air pocket can be an early radiologic hallmark of a mycotic aneurysm. Case Report Our patient is a 76-year-old man who had a history of diabetes mellitus and hyperten- sion for more than 10 years before hospital- ization in the case in question. The patient had undergone coronary artery bypass graft sur- gery for coronary artery disease 9 years ear- lier, and peripheral arterial occlusive disease necessitated amputation of the right foot and femoral artery bypass surgery 3 years ago. The patient visited our emergency depart- ment because of a sudden onset of fever and chills. Laboratory analysis of a blood sample did not reveal leukocytosis but did detect Sal- monella. A complaint of slight abdominal pain prompted a CT examination (LightSpeed 16, GE Healthcare). Contrast-enhanced CT was not performed because of renal insufficiency. The unenhanced MDCT scans showed focal fusiform dilatation of the lower abdominal aorta at the level of the inferior mesentery ar- tery. The surrounding fat planes were clear. Atherosclerosis-related focal abdominal aneu- rysm was considered. In addition, a small air pocket was identified on the left side of the ab- dominal aortic wall at the renal level; the air pocket was surrounded by mild fatty infiltra- tions (Fig. 1A). A mycotic aneurysm was con- sidered at this area. The mycotic and the fusi- form aneurysms could be seen concurrently on the sagittal reformatted image (Fig. 1B). After the patient had received antibiotics for 8 days, follow-up MRI (Magnetom So- nata, Siemens Medical Solutions) showed a focal lobulated saccular aneurysm arising from the area where the air pocket had been— that is, on the left side of the aortic wall at the renal level with increased areas of periaortic fatty stranding (Fig. 1C). There was no defi- nite interval change or dirty fat planes around the lower abdominal aortic aneurysm. The patient’s condition improved as a re- sult of the medical treatment. Follow-up MRI conducted 2 weeks after the initial MRI ex- amination (3 weeks after initial presentation) showed the partial mural thrombus in the my- cotic aneurysm had not changed in size since the initial CT examination. The periaortic in- filtrations were significantly improved with adjacent clear fat planes. The patient’s condi- tion stabilized with no relapse of fever. Therefore, he was discharged and was fol- lowed up on an outpatient basis. Discussion Atherosclerosis is considered to be a cause of weakening in the arterial wall that results in abdominal aortic aneurysm. Atherosclerosis is a multifactorial process that is influenced by hypercholesterolemia and modified lipids, lipoproteins, homocysteine, and infection [2]. Abdominal aortic aneurysm is also a familial disorder, being possibly genetic or polygenic in origin [3]. Transient bacteremia leading to hematoge- nous infection of atherosclerotic vessels is the most common cause of mycotic aneurysm. In patients with salmonellosis cultured from sputum, blood, or urine without an adequate explanation of the bacterium’s origin, intra- vascular infection must be suspected [4]. The incidence of aortic infection in patients with nontyphoid Salmonella bacteremia is high in Taiwan [5]. Timely surgical intervention and prolonged IV antibiotic therapy have resulted in excellent outcomes. CT features of mycotic aneurysm of the aorta include a hazy aortic wall with rupture, M Downloaded from www.ajronline.org by 52.73.204.196 on 05/13/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved