Mycotic Aneurysm

A mycotic aneurysm is a dilatation of an arterial wall due to an infectious process. The term "mycotic" was coined by William Osler in his where he described a man with multiple aortic mycotic aneurysms that resulted from cardiac valve vegetation, resembling a fleshy fungus. However, this description does not suggest a fungal etiology, as the majority of infected aneurysms are caused by bacterial pathogens. Infectious aortitis refers to a vascular infection without aneurysmal dilation. An infected aneurysm usually develops in the presence of a preceding systemic infection with bacteremia or through direct invasion of the blood vessel wall in a preexisting aneurysm or atheromatous plaque.  The risk of a mycotic aneurysm is higher in immunocompromised individuals, including those with HIV infection, diabetes mellitus, or malignancy, as well as those receiving high-dose glucocorticoids or chemotherapy. The most commonly affected blood vessels, in order of frequency, include the aorta, intracranial vasculature, and femoral and visceral arteries (eg, superior mesenteric and splenic). The natural history of these aneurysms is characterized by expansion, leading to pseudoaneurysm formation, where rupture is contained, followed by eventual rupture, hemorrhage, sepsis, and multiple organ failure. Mycotic aneurysms are among the most challenging clinical problems for vascular surgeons due to their associated perioperative mortality.