Table 2.

Differential table for Mycobacterium bovis mycotic aneurysms

	Mycobacterium bovis mycotic aneurysm	Inflammatory aneurysm	Atherosclerotic aneurysm	Contained aneurysm rupture	Aortoenteric fistula
Clinical history	History of BCG therapy for bladder cancer Mean age 71 M >> F Weight loss/fever +Cultures for M. bovis	Similar risk factors as for atherosclerotic Typically younger (40–50s) Back pain, fever, weight loss Elevated ESR	Elderly (M > F) Atherosclerotic risk factors	Same as for atherosclerotic aneurysms Acute onset back/abdominal pain Acute - hypotension	Presents with brisk GI bleed Risk factors: surgical AAA repair, infectious aortitis, PAU, tumor invasion, XRT
X-ray	Typically normal	Typically normal	Enlarged aorta (with calcified walls)	Typically normal	Typically normal
US	Rapidly enlarging, focal saccular “yin-yang” color flow Perivascular soft tissue	Fusiform dilatation of the infrarenal aorta and iliacs May see thickened aortic wall	Fusiform dilatation of the infrarenal aorta and iliacs Vascular plaque common	Ill-defined aneurysm sac with peri-aneurysmal fluid Poor sensitivity	Non-specific (not sensitive)
CTA	Rapidly enlarging focal saccular aneurysm Perivascular soft tissue inflammation (stranding, edema, fluid) Thoracoabdominal aorta > peripheral vascular system > carotids > coronaries	Fusiform infrarenal AAA and iliac aneurysms Thickened aortic wall May see findings of retroperitoneal fibrosis	Fusiform infrarenal AAA and iliac aneurysms Calcified and fibrofatty wall plaque common Most common aneurysm type in the coronaries	Calcified aneurysm with focal wall discontinuity Retroperitoneal hematoma Draping of posterior aorta over vertebral body	Loss of fat plane between aorta and adjacent bowel loop Gas in the aorta Arterial-phase opacification of bowel on CECT, increases with delayed phases
MRI	Rapidly enlarging, focal saccular Perivascular edema (low T1, high T2) May see adjacent inflammation or abscess	Fusiform infrarenal AAA and iliac aneurysms Thickened aortic wall Perianeurysmal soft tissue (low T1, high T2, enhancing)	Same as for CT	Same as for CT (not typically used in cases of suspected acute rupture)	Same as for CT but less sensitive
Angiography	Focal, saccular aneurysm May see active extravasation if acutely ruptured	Fusiform infrarenal AAA and iliac aneurysms	Fusiform arterial dilatation	Active arterial extravasation Pseudoaneurysm	Active arterial extravasation into bowel