The role of imaging techniques in evaluating possible graft infections.

Imaging plays a central role in the management of graft infections. Most graft infections are clinically apparent, and imaging techniques are used primarily for diagnostic confirmation and operative planning. The accurate diagnosis of less overt graft infections requires a thorough understanding of the available imaging options. Late aortic graft infections (more than 3 months postoperative) are best evaluated initially by computed tomography (CT) or magnetic resonance (MR) scanning. CT findings consistent with a graft infection include ectopic gas, perigraft fluid, perigraft inflammatory changes, anastomotic pseudoaneurysm, and thickening of adjacent bowel. MRI offers the additional advantage of T2-weighted images to identify perigraft inflammation and minute quantities of perigraft fluid. Radionuclide scanning techniques such as 111indium-labeled WBC scans are highly sensitive but suffer from a relative lack of specificity. Duplex ultrasonography is best applied to the diagnosis of late infections of superficial grafts. Sonographic findings of a graft infection include perigraft fluid and pseudoaneurysms. The imaging of early postoperative grafts (less than 3 months) for infection is problematic because perigraft fluid and inflammatory changes persist for up to 3 months postoperatively. Suspected early graft infections often require operative exploration for diagnosis. A thorough understanding of the utility and limitations of imaging techniques will enable the clinician to develop a reasonable diagnostic algorithm that is appropriate for each case.