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|Year : 2011 | Volume
| Issue : 1 | Page : 52-53
FDG positron emission tomography/computed tomography in the detection of aortic endograft infection
SG Dua, NC Purandare, S Shah, V Rangarajan
Bio-Imaging Unit, Tata Memorial Hospital, Parel, Mumbai - 400 012, India
|Date of Web Publication||31-Jan-2011|
Bio-Imaging Unit, Tata Memorial Hospital, Parel, Mumbai - 400 012
|How to cite this article:|
Dua S G, Purandare N C, Shah S, Rangarajan V. FDG positron emission tomography/computed tomography in the detection of aortic endograft infection. J Postgrad Med 2011;57:52-3
|How to cite this URL:|
Dua S G, Purandare N C, Shah S, Rangarajan V. FDG positron emission tomography/computed tomography in the detection of aortic endograft infection. J Postgrad Med [serial online] 2011 [cited 2015 Jan 25];57:52-3. Available from: http://www.jpgmonline.com/text.asp?2011/57/1/52/74292
A 56-year-old man underwent a positron emission tomography/computed tomography (PET/CT) study to investigate his fever of unknown origin. Laboratory parameters were unremarkable, except for leucocytosis and elevated C-reactive protein. He was a known diabetic and hypertensive, on treatment since 15 years and had undergone endovascular stent-grafting for an atherosclerotic aneurysm of the descending thoracic aorta about two years back. Focal increased tracer uptake was seen on the PET image [Figure 1]a and b, which localized to the wall of the descending thoracic aorta at the site of the stent graft on the fusion images [Figure 1]c and d. The corresponding CT image [Figure 1]e and f however, merely showed non-specific wall thickening. In keeping with clinical presentation and PET/CT findings a diagnosis of endograft infection (EI) was rendered. Subsequently, the patient underwent endograft explantation and reconstruction with extra-anatomic bypass. Microbial culture revealed growth of staphylococcal species confirming the clinico-radiologic suspicion of EI. The postoperative course was uneventful and the patient is being followed up.
|Figure 1: Focal increased tracer uptake is noted in the PET image (a, b), which localized to the wall of the descending thoracic aorta in the region of the stent on the fusion image (c, d) suggesting endograft infection. Note: the CT image (e, f) reveals mere non-specific wall thickening at the corresponding site|
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In recent years there has been a steady increase in the number of endovascular aortic aneurysm repairs (EVAR), attributable to reduced perioperative complications vis-à-vis open surgical grafting. The concern in the follow-up of patients with EVAR is primarily centered on the technical aspects of the procedure like endoleaks, stent migration and limb occlusion. EI is an infrequent but serious complication of EVAR and is associated with significant mortality, thereby requiring prompt diagnosis and treatment. Patients with early EI often present with non-specific symptoms like fever, malaise and weight loss and as a result the diagnosis is delayed.  This places the emphasis of timely detection on imaging modalities, of which CT is the most widely used and studied. However, the CT findings in the early stages are often inconclusive,  indicating a need for a more sensitive modality. This was seen in our patient, where the CT study was unremarkable except for minimal wall thickening at the site of the stent graft. The diagnosis was in fact suggested by the abnormal tracer uptake noted on the PET image, which led to prompt removal of the stent graft.
PET/CT combines the benefits of both anatomical and functional imaging and is being increasingly used in the management of patients with aneurysms of the aorta. The finding of increased tracer uptake in the aneurysm correlates with high wall stress at the site of the aneurysm. This in turn puts the aneurysm at the risk of rapid expansion and rupture and often requires emergent implementation of surgical bypass grafting. , Increased tracer uptake may also serve as a marker of infection, as in mycotic aneurysms.  PET/CT is also used in the detection of prosthetic vascular infection in the subset of patients that have undergone bypass grafting, and has shown high accuracy. , However, there are no studies investigating the role of PET/CT in the detection of EI. Results of the above , and similar studies can be extrapolated and PET/CT can be used in cases where EI is suspected as shown. In addition PET/CT can also help in uncovering a remote site of infection which sometimes is the source of endograft infection.
Our case thus brings to light the incremental and emerging role of PET/CT in patients presenting with symptoms suspicious for EI. Timely referral for a PET/CT by an informed clinician can thus be invaluable in making the diagnosis and initiating the appropriate treatment in order to avoid disastrous and often fatal complications.
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