PMC9650533_01
Multimodality imaging of periaortic mass of the abdominal aorta. (A-D) Axial images. (A) Unenhanced CT image showing a non-dilated abdominal aorta with a maximum diameter of 17 mm including mural calcification surrounded by circumferential heterogeneous soft-tissue density (arrowheads). (B,C) Unenhanced abdominal magnetic resonance image. (B) FsT2WI showing significantly high signal intensity and marked thickening of the periaortic tissue of the abdominal aorta (arrowheads) with inhomogeneous diffusion restriction on DWI (C). (D) Ga-single photon emission computed tomography/CT image revealing an active accumulation of Ga (arrowheads) corresponding to the periaortic mass. CT, computed tomography; DWI, diffusion-weighted imaging; FsT2WI, fat-suppressed T2-weighted image; Ga, gallium citrate-67.
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F1
Unenhanced CT revealed a non-aneurysmal dilation of the infrarenal abdominal aorta with increased soft tissue mass around the aorta (Figures 1A, 2A). T2 and diffusion-weighted imaging (DWI) showed a high-intensity area around the aorta with diffusion restriction (Figures 1B,C). Furthermore, gallium-67 single-photon emission computed tomography (Ga-SPECT)-CT showed abnormal uptake in the corresponding area, confirming active inflammation (Figure 1D). Additionally, an aortic mural thrombus was observed on the anterior wall of the descending thoracic aorta (Supplementary Figure 1A). The early postoperative MRA revealed abnormal intensity around the vascular graft highly suggestive of vascular graft infection (Supplementary Figure 1B). After follow-up blood examination and MRA confirmed the resolution of an inflammatory response to the infection (Supplementary Figures 1C,D), the antimicrobial therapy was de-escalated to oral cefalexin (250 mg every 8 h).
Serial unenhanced CT and MRA assessment of the abdominal aorta. (A-C) Serial unenhanced reconstructed coronal CT image showing no significant change in the periaortic mass of the abdominal aorta (white arrowheads). (D) Initial TS-MIP image of the original MRA image showing several asymmetric aortic dilatations in the abdominal aorta (yellow arrowheads). (D-F) Serial TS-MIP of the original MRA image showing rapid aortic expansion with multilobular protrusion of the abdominal aorta to the left side (yellow arrowheads). CT, computed tomography; MRA, magnetic resonance angiography; TS-MIP, thin-slab maximum intensity projection.
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F2
Unenhanced CT revealed a non-aneurysmal dilation of the infrarenal abdominal aorta with increased soft tissue mass around the aorta (Figures 1A, 2A). The periaortic soft tissue lesion appeared stable on serial CT imaging (Figures 2A-C). Nevertheless, serial unenhanced magnetic resonance angiography (MRA) with thin-slab maximum intensity projection (TS-MIP) demonstrated acutely progressive morphological changes of the abdominal aorta characterized by multilobular and saccular features strongly suggestive of infectious pseudoaneurysm formation (Figures 2D-F). Arthrobacter russicus sequences were obtained via 16S rRNA sequencing (Supplementary Figures 2-4), leading to the potential causative microorganism. A careful interview revealed that she was a farm worker with multiple exposures to soil and frequent episodes of foreign body ingestion related to dementia.
Operative view and pathological findings. (A,B) Intraoperative view before (A) and after (B) the repair using a Dacron graft. (C) The resected abdominal aortic aneurysm shows severely calcified plaque as well as several recesses with adherent mural thrombi (red arrowheads). (D-F) Photomicrographs of the resected abdominal aorta (longitudinal sections around the black line in C) with Masson's trichrome stain (D), Elastica van Gieson staining (E), and hematoxylin and eosin staining (F) showing marked inflammatory infiltration of the aortic wall (white arrowheads) and pseudoaneurysm formation (black arrowheads) due to loss of the normal structure of the aortic wall as well as cholesterol crystals (blue arrows). (G) A high-power view with hematoxylin and eosin staining showing intense perivascular inflammatory infiltrates (magnified view of the black box in F) but no microorganisms (white arrowheads). (H) Notably, the magnified view of the black box in (G) shows the accumulation of nuclear debris (arrows). Bars: (D-F), 500 mum; and (G,H), 20 mum. *Vascular lumen. The red arrow depicts a fibrous cap, while "m," "a," and "n" depict the media, adventitia, and neointima, respectively.
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F3
On day 30, she underwent open surgical repair of the infected aortic lesion using an in situ graft (GORE-TEX Vascular Graft) (Figures 3A,B). Pathology of the excised aorta revealed severely calcified atherosclerosis with inflammatory cell infiltrations predominantly consisting of neutrophils, fresh mural thrombus, and partial pseudoaneurysm formation but without obvious bacteria (Figures 3C-3H). Arthrobacter russicus sequences were obtained via 16S rRNA sequencing (Supplementary Figures 2-4), leading to the potential causative microorganism. A careful interview revealed that she was a farm worker with multiple exposures to soil and frequent episodes of foreign body ingestion related to dementia.