A protruding sign in the aortic aneurysm neck

Clinical History

Patient admitted to the hospital for undergoing endovascular repair of an infrarenal abdominal aortic aneurysm.

Imaging Findings

The patient was admitted to the hospital for undergoing endovascular repair of an infrarenal abdominal aortic aneurysm. The patient had a history of ischemic heart disease and an aortic aneurysm was detected on abdominal ultrasound. Contrast-enhanced helical computed tomography (CT) demonstrated that an aneurysm-like lesion was located in the proximal aneurysm neck and posterior to the aortic aneurysm (Fig 1a). This imaging appearance was best demonstrated on multiplanar reformation (MPR) and maximum-intensity projection (MIP) images (Fig 1b,c). Considering the patient’s age and general situation, an endovascular stent grafting was chosen to treat the aortic aneurysm. However, due to the protruding appearance in the proximal aneurysm neck, a suprarenal stent grafting was selected to ensure the proximal fixation and prevent possible complications such as endoleak or stent graft migration. Post-operative CT images showed that the aneurysm was successfully excluded from the circulation and no complications were observed (Fig 2a,b). The stent graft was deployed across the renal arteries and just below the superior mesenteric artery (SMA). Post-operative virtual endoscopic images confirmed that SMA and renal arteries were patent, although they were shown to be peripherally encroached by suprarenal stent struts (Fig 2c-e).

Discussion

Stent-graft fixation in an unsuitable aneurysm neck carries the risk of technical failure owing to development of a proximal endoleak or stent-graft migration. Placement of an uncovered suprarenal component over the renal arteries has been proposed to improve the fixation of stent-grafts in patients with short and difficult aneurysm necks (1,2). A focal protrusion in the aneurysm neck makes it difficult for the aortic aneurysm to be treated with conventional infrarenal stent grafting but will benefit from the suprarenal stent grafting. This is due to the supposition that the focal protrusion in the aneurysm neck poses danger for the attachment of the stent graft to the aortic wall and may result in post-operative complications such as endoleak or stent migration. This complicated situation can be overcome by deploying the suprarenal component in a relative good quality aorta above the renal arteries as it was reported that diameters of the suprarenal aorta did not change while the infrarenal aortic neck demonstrated continued dilatation following endovascular aortic repair (3). A significant decreased risk of proximal type I endoleak without any increase in early morbidity or risk of renal dysfunction has been reported in patients treated with suprarenal stent graft fixation as opposed to infrarenal fixation (4).
3D postprocessing techniques such as MPR and MIP are the commonly used techniques in assessing the aortic stent grafting both pre- and post- operatively (5). These postprocessing methods offer additional information regarding the type of aneurysm and its relationship to the aneurysm neck and aortic branches when compared to conventional 2D images. A recently developed 3D imaging technique virtual endoscopy is able to present intraluminal views of the aorta, its branches as well as 3D relationship between stent struts and the aortic ostia. This was clearly demonstrated in our case showing that the SMA and renal ostia were crossed by suprarenal stent struts.
Our report in this case study shows that use of 3D imaging techniques helps to clarify complex anatomical structures and aid pre-operative planning and assess post-operative treatment. A combination of various imaging methods will provide us with more information which cannot be normally obtained from conventional 2D images. This is especially apparent in the visualisation of the 3D relationship between stent struts and the aortic ostia following suprarenal stent grafting, where virtual endoscopy plays a superior role in the particular area. This should be brought to attention to the radiologists and vascular surgeons in imaging centres when dealing with endovascular repair of aortic aneurysms.

Differential Diagnosis List

Final Diagnosis

Focal protrusion of the aortic aneurysm in the proximal aneurysm neck

URL:	https://www.eurorad.org/case/2564
DOI:	10.1594/EURORAD/CASE.2564
ISSN:	1563-4086