Mycotic aneurysm

Last revised by Dr Daniel J Bell on 13 Jun 2022

Mycotic aneurysms are aneurysms arising from infection of the arterial wall, usually bacterial. It is a complication of the hematogenous spread of bacterial infection, classically from the heart

Mycotic aneurysms are thought to represent only a minority of (0.65-2.6%) of all aortic aneurysms 10-13.

The epidemiology of mycotic aneurysms mirrors that of identifiable risk factors: 

The vessel wall becomes infected with bacteria, is digested, and false aneurysm forms, which is unstable and highly prone to rupture. The most common organisms are Staphylococcus aureus and Salmonella spp. Mechanisms of infections include:

  • septicemia
  • septic emboli
  • contiguous spread from adjacent infection

Frequently found in atypical locations. The most common sites are:

Described features include the following (some are however non-specific):

  • saccular
  • centric aneurysmal sac in an odd location for atheromatous disease
  • often wild, multilobulated appearance
  • interruption of arterial wall calcification
  • adjacent soft tissue stranding
  • adjacent collection +/- gas
  • adjacent reactive lymphadenopathy
  • hazy aortic wall with rupture 4
  • retroperitoneal para-aortic fluid collection and vertebral erosion
  • thrombus formation within a false lumen after aneurysmal rupture

Mycotic aneurysms carry a very high mortality.

  • aneurysmal rupture (high risk) with hemorrhage
  • an ongoing source of sepsis
  • embolic infarction

The term "mycotic" (meaning fungus) was coined in 1885 by Canadian physician William Osler (1849-1919) on describing the gross pathological appearance of two small saccular aortic aneurysms, not the underlying pathological organism 9

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Cases and figures

  • Case 1: axial
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  • Case 1: coronal
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  • Case 2: bilateral
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  • Case 3
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  • Case 4
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  • Case 5
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  • Case 6: with SAH
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  • Case 6: DSA
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  • Case 7
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  • Case 8: fungal aortitis with mycotic aneurysms
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  • Case 9: tuberculosis
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  • Case 10
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  • Case 11: ICA pseudoaneurysm
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