Infected (mycotic) aneurysm: a cause of fever without focus

73 year-old male with fever of 10 days of evolution without a clear focus. Leukocytosis. On computed tomography (CT): focal, contrast-enhancing saccular dilatation arising from the right lateral of the infrarenal aorta. Periaortic fat stranding. No active extravasation of intravascular contrast material.

Infected aneurysm or mycotic aneurysm is defined as an infectious break in the wall of an artery with formation of a blind, saccular outpouching that is contiguous with the arterial lumen. They are uncommon (0,7-1% of all surgical treated aortic aneurysms) but can affect any artery. The abdominal aorta is the most common location. Infected abdominal aortic aneurysms usually manifest as abdominal pain with or without a pulsatile mass. Staphylococcus are the most common causes of infected aneurysms, however up to 25% of blood cultures are negative. On CT we can appreciate early changes of aortitis include irregular arterial wall, periaortic edema (fat stranding concentric rim), periaortic soft-tissue mass and periaortic gas. The aneurysm appears as a focal, contrast-enhancing saccular dilatation. We can also see a disrupted arterial wall calcification. Rupture shows active extravasation of intravascular contrast material and hematoma formation adyacent to the aneurysm. They usually have a poor natural history, with high morbidity and mortality from haemorrhage or fulminant sepsis.

CT is the current imaging modality of choice for the evaluation of suspected infected aneurysms. CT is necessary to establish the diagnosis, to localize and to identify associated complications. Prompt diagnosis is essential for optimal outcome in the management.

- Lee W, Mossop P.J., Little A.F., Fitt G.J., Vrazas J.I., Hoang J.K. et al Infected (mycotic) aneurysms: spectrum of imaging appearances and management. Radiographics, 2008, 28:1853-1868. - Macebo T.A., Stanson A.W., Oderich G.S., Johnson M., Panneton J