Spontaneous Thrombosis of an Isolated Internal Iliac Artery Aneurysm.

Abstract Objectives : Isolated internal iliac artery aneurysms (IIAAs) are uncommon but potentially morbid lesions that are a challenge to monitor and treat. However, given the small numbers of reported cases and high rates of incidentally discovered lesions, the natural history of isolated IIAAs is not well characterized. This case describes an atypical and previously unreported spontaneous thrombosis of an isolated IIAA, a lesion typically thought to progressively enlarge and rupture. Methods: Medical records and imaging studies were retrospectively reviewed with the approval of our Institutional Review Board. A single patient underwent fluoroscopic angiography followed by computed tomography (CT) angiography, with no subsequent operative intervention. Results: An isolated 5.5cm left IIAA was discovered incidentally on CT scan and subsequently seen with fluoroscopic pelvic angiography. Three weeks following initial angiography, repeat pelvic angiography and CT scan demonstrated spontaneous thrombosis of the aneurysm. Conclusions: Isolated IIAAs are conditions for which the natural history remains uncertain despite their potential risk for rupture and mortality. Spontaneous thrombosis of these lesions is possible, suggesting that the natural history as previously described warrants further consideration.