Endoleak after Endovascular Aneurysm Repair
Related narrative: Explantation of Aortic Endograft for Type I Endoleak
Endoleak after Endovascular Aneurysm Repair Endovascular aneurysm repair (EVAR), while not applicable to all abdominal aortic aneurysms, compares favorably to traditional open repair in several short-term outcome measures, including cardiopulmonary complications, in-hospital mortality, and length of inpatient stay. The long-term durability of EVAR, however, is unknown and there are several EVAR-specific complications. The most common complication is endoleak, defined as continued perfusion of the aneurysm sac.
The incidence of endoleak after EVAR varies amongst series. In the large Eurostar registry, the total prevalence of endoleak during a mean follow-up of 15.4 months was 19.8%, roughly 1/3 of which were identified within the first month. There are four defined types of endoleak:
Type I: Attachment Site Leak
Type II: Branch Leaks (without attachment site leaks)
Type III: Graft Defect
Type IV: Fabric porosity
Due to uncertainty regarding sac behavior after EVAR and a significant incidence of delayed endoleak, long-term surveillance of patients is essential. Biphasic CT scanning is most commonly used, although duplex, MRA, and even plain films have utility. Conventional angiography is the gold standard and despite its invasive nature and known risks, it has the distinct advantage of allowing for a concomitant therapeutic procedure. Type I leaks mandate intervention due to the increased risk of aneurysm rupture. The treatment should be endovascular if possible, due to a high rate of perioperative mortality of 7% - 24%. If there is sufficient native aorta, extender cuffs or large Palmaz stents may be utilized. Embolization of the endoleak cavity with coils or liquid glue has been reported but carries with it the serious risk of ischemic injury from nontarget embolization. Operative endograft explantation can be difficult, especially with devices that have external hooks or suprarenal fixation. These often require suprarenal or even supraceliac clamping. Partial graft preservation can be safely performed and may simplify an otherwise challenging operation.
The natural history of Type II endoleaks is poorly defined and considerable debate exists as to their significance and the need to intervene on them. Although they can lead to rupture, Type II leaks tend to have a benign course and a significant percentage will resolve spontaneously. Close surveillance is critical if a watch-and-wait approach is used, since the long term significance is unknown and also since Type I and Type III leaks can sometimes masquerade as a Type II leak. There is no consensus on when to intervene: some use an enlarging aneurysm sac as an indication, others use an arbitrary time deadline. Endovascular techniques can often be used to correct Type II leaks, either with transarterial or translumbar embolization of patent branch vessels.
Type III endoleaks are similar to Type I endoleaks in that they are associated with subsequent aneurysm rupture. Modular limb disconnections (Type IIIA) are more common than fabric erosions (Type IIIB) and were generally seen with 1st generation devices. These require correction, which can usually be achieved with endovascular deployment of a covered stent to realign the failing endograft.
Type IV endoleaks are difficult to diagnose. They are usually a diagnosis of exclusion when no other source of endoleak can be identified. They have a benign course and almost always resolve spontaneously, usually within 1 month.
This case presentation illustrates several unique features regarding the presentation, diagnosis, and management of endoleaks. The diagnosis of Type I leak was delayed for several months because the CT appearance was more consistent with Type II leak. Angiography was required for definitive diagnosis and should be used liberally when there is any question as to the etiology of an endoleak. This also emphasizes the need for constant surveillance of endoleaks, as a Type II leak can masquerade as a more serious Type I or Type III leak.
Type I leaks require correction due to a risk ratio for late rupture of 7.59. Endovascular treatment was not possible in this patient and therefore surgical correction was promptly performed. This case also illustrates the successful use of endograft preservation during surgical endoleak correction. Leaving the distal limbs intact allowed for antegrade pelvic perfusion while minimizing the risk of iliac artery, iliac vein, and ureteral injury with a difficult pelvic dissection.
R. Eugene Zierler, M.D.
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