Table 2.

Differential diagnosis table for IgG4 Aortitis.

Differential diagnosis	Transesophageal echocardiogram (TEE)	Computed Tomography (CT)	Magnetic Resonance Imaging (MRI)	Fluorodeoxyglucose-Positron Emission Tomography (FDG-PET)
Atherosclerosis	Intimal thickening with areas of ulceration, calcification, or fibrous cap.	Eccentric wall thickening with a low-density atheromatous plaque that may or may not be calcified.	MRI demonstrates eccentrically located T1 and T2 hypointense plaque along the aortic wall. MR angiography better defines the aortic wall and outlines the plaque.	Rarely used
Intramural hematoma (IMH)	Rarely used	Considered the diagnostic modality of choice due to its rapid scan time in an emergent setting. Demonstrates crescentic aortic wall hyperattenuation best seen on nonenhanced sequence. Subacute IMH may be isoattenuating. CTA demonstrates decreased luminal diameter with a non-enhancing eccentric wall thickening.	Rarely used on initial scanning. MRI can play a role in follow-up imaging post stent repair of acute aortic syndrome.	Rarely used
Vasculitis or Aortitis	Rarely used	Concentric vessel wall thickening. Vessel wall calcifications – seen in chronic inflammation. CTA can demonstrate thrombosis, stenosis, occlusion, or aneurysm.	MRI can demonstrate early wall thickening and edema on T2 weighted imaging. Contrast enhanced MRI can demonstrate enhancement of the thickened wall. MRA findings can demonstrate thrombosis, stenosis, or occlusion.	PET demonstrates increased sensitivity for extra-aortic inflammation. FDG uptake usually correlates with disease activity.
Infection	Rarely used	Considered the diagnostic modality of choice. CT appearance of infectious aortitis can vary: arterial wall thickening, periaortic fluid collection, soft-tissue accumulation, rapidly increasing aneurysm or pseudoaneurysm and occasionally air.	Rarely used	Rarely used