The differential diagnosis of an aortic graft infection includes endocarditis, wound infection, and septic thrombophlebitis with a right-to-left shunt, such as a patent foramen ovale. There is no clear consensus on how to best diagnose infected grafts, but a CT scan with IV contrast is the primary test of choice. Previous studies have shown CT scanning to have a sensitivity of 64% to 100% and a specificity of 85% to 100%. The sensitivity is reduced significantly in patients with indolent and/or low-grade infections, accounting for some of the variability. The CT scan findings characteristic of graft infections include perigraft fluid, soft tissue attenuation or gas, and pseudoaneurysm. However, it may be difficult, as in our case, to distinguish radiographic changes due to surgery from changes secondary to infection. Advantages of CT scan are lower cost, rapidity of scanning, ready availability, and potential for CT scan-guided percutaneous aspiration of perigraft fluid. Indium-labeled WBC scans can be useful when CT scan findings are inconclusive and can be diagnostic of late graft infections; they have a reported sensitivity of 60% to 100% and a specificity of 87% to 100%. Indium labeled imaging is limited in that it is time consuming, can be falsely positive from inflammation due to other causes, and may be falsely negative because of prior antibiotic therapy. MRI is often used when CT scan results are inconclusive; it offers better visualization of perigraft fluid and can differentiate subtle inflammatory changes from a hematoma. Its sensitivity and specificity are not clearly defined in the literature. PET scans are emerging as a promising diagnostic imaging modality that may be superior to CT scans; however, data on this diagnostic modality are still limited and more studies are needed. One study of 11 patients revealed a sensitivity of 91% and specificity of 95% in diagnosing a graft infection when defining a focal abnormal uptake as the criterion for infection. Disadvantages of PET scans include high cost, time-consuming processing, and an inability to localize the precise site of graft infection unless correlated with a CT scan. Microbiologic investigation, including serial blood cultures and cultures of wound drainage or CT scan-guided aspirates of perigraft fluid, can lead to a preoperative identification of the causative pathogen in approximately 60% of cases and may guide antibiotic therapy. Intraoperative cultures from the actual graft and surrounding tissues are the gold standard in isolating the causative pathogen(s). The graft tissue specimens should be submitted for bacterial, fungal, and mycobacterial cultures. The most common causative organisms of graft infections are Staphylococcus species, with MSSA more common in early infections and Staphylococcus epidermidis more common in late infections. Gram-negative bacilli, enterococci, anaerobes, and candida species may be recovered but may represent colonization when recovered from superficial wound cultures as opposed to operative cultures. Polymicrobial infections are less frequently encountered (14%) but portend a worse prognosis.