May 13, 2021
A 60-year-old asymptomatic man with a history of HIV and persistently low CD4 counts presents for follow-up of abnormality on lung screening CT.
Infectious Aortic Aneurysm with Vertebral Involvement
- Background:
- Infectious (also known as “mycotic”) aortic aneurysms are relatively rare and can develop from (1) septic embolism, (2) bacteremia with seeding of damaged endothelium, or (3) direct extension of infection.
- Spinal involvement is uncommon and can result from arterial pulsation with chronic osseous ischemia and bone remodeling or direct osseous extension of infection.
- Patients with immunosuppression are at increased risk: HIV, posttransplant, cancer, and others.
- Clinical Presentation:
- Patients most commonly present with abdominal or back pain but may be asymptomatic, as in this case.
- Key Diagnostic Features:
- Most cases are bacterial; Staphylococcus spp. are most common, followed by Salmonella (the current case was secondary to Bartonella henselae with positive serum titers). The term “mycotic” is a misnomer and was originally used to describe a mushroomlike appearance.
- Infectious aneurysms are essentially contained ruptures with pseudoaneurysm formation.
- There may be scalloping/erosion of the surface of the adjacent vertebral body.
- Presence of periaortic gas is variable depending on the nature of the germ and the fistulization to gas-filled cavities.
- Enhancement of arterial wall and perivascular tissues is best demonstrated on MRI, which should include STIR or fat-suppressed T2 and fat-suppressed postcontrast T1. Osseous involvement (ie, osteomyelitis) is best demonstrated on MRI with increased STIR/T2 signal and enhancement.
- May be accompanied by varying degrees of thrombosis
- Differential Diagnoses:
- Sarcoma: May have foci of necrosis, hemorrhage, or fat (liposarcoma); would not partially encase the aorta while respecting its lumen; direct bone involvement usually results in a more permeative appearance.
- Lymphoma: Can displace the aorta but typically has a more homogeneous appearance with relatively low T2 signal intensity and avid enhancement; osseous involvement results in a more permeative appearance or sclerosis of the vertebral body.
- Abscess: Can accompany an infectious aneurysm; would result in a usually T2-hyperintense fluid collection with peripheral enhancement
- Treatment:
- Aggressive antibiotic therapy, surgical debridement, and vascular reconstruction
- The prognosis is poor.
- The current patient was not an operative candidate due to medical comorbidities. He was treated with an extended course of antibiotics followed by endovascular stent placement.
