Postoperative Findings

Postoperative imaging appearances differ after various surgical repairs and after percutaneous endoprosthesis insertion. Some of the complications encountered also differ. Knowledge of specific therapeutic technique used is necessary for postoperative imaging evaluation. Delayed aneurysm rupture after endovascular repair is rare. Normal Imaging Serial postoperative contrast-enhanced CT or MR identifies most major complications after surgical repair, including bleeding, false aneurysm formation, vessel occlusion, and mostfistulas. With an end-to-end anastomosis, the native aneurysm wall is wrapped around a graft. Postoperative fluid is common between a graft and native aorta and is detected with CT or MR. Perigraft fluid in some patients persists for several months. This fluid is gradually reabsorbed; increasing amounts of fluid with time suggest infection. Postoperative surveillance includes measurement of residual aneurysm size. A measure of maximum residual aneurysm diameter using CT angiography is common, although aneurysm volume is probably more accurate.
Magnetic resonance imaging is limited in the immediate post perative period if metal components are present. Covered nickel titanium stent-grafts used for abdominal aortic aneurysm repair have been safely imaged by 1.5-T MRI, with no ferromagnetism or heating detected. In an in vitro contrast-MR study
of nitinol, tantalum, stainless steel, and cobalt alloy stents, only the latter stent resulted in a signal void inside the lumen; MR of some of the stents produces an artificial diameter narrowing.
A CT scan 24 to 48 hours after graft placement should reveal any partial or complete thrombosis of the aneurysmal sac; initially patent channels tend to close subsequently, but can recur. A mottled appearance within the aneurysmal sac is not uncommon. Maximum intensity projections rendered from helical CT a week or so after aortic stent graft placement is useful to evaluate stent deformity or stent angulation; MIP also aids in detecting renal
artery occlusion, leaks and thrombi. Computed tomography criteria of successful endovascular repair consist of a decrease or unchanged size aneurysmal sac without the presence of perigraft channels; the latter are often associated with subsequent aneurysm enlargement. Eventual fibrosis surrounding the surgical site appears hypointense with both T1- and T2-weighted images. Some evidence suggests that MRA is as sensitive as CTA in detecting endoleaks it also avoids iodinated contrast agents Eventual fibrosis surrounding the surgical site appears hypointense both with T1- and T2-weighted images.
No firm guidelines are established for longterm follow-up of asymptomatic patients after endovascular repair. Pre- and postcontrast CT scans annually appear reasonable. Any symptoms or known complication require more frequent follow-up.
This is radiology images of the abdominal aortic aneurysm repair. A 3D reconstruction (A) and maximum intensity projection (MIP) reconstruction (B) identify relationship of aorta to adjacent structures.
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