Comparison of Contrast Enhanced Ultrasound and the Gold Standard Computed Tomographic Angiography in Detection of Endoleak Following Endovascular Abdominal Aortic Aneurysm Repair.

Background:

Abdominal aortic aneurysms (AAAs) continue to be a leading cause of death in older age groups. In the 60-85 year-old population, AAA represents the 14th-leading cause of death. Federal funding through Medicare has been allocated for early detection using abdominal ultrasound screening programs. Despite these more aggressive screening programs and concerted efforts by surgeons for timely repair, the incidence of ruptured AAA has continued to increase.

Endovascular aneurysm repair (EVAR) has been the most common type of repair since 2006. Multiple studies reflecting decreased perioperative morbidity and mortality over open repair make this an attractive option for patients. EVAR requires more intensive follow-up than standard open surgical repair, however. Secondary interventions are more common to maintain "seal" of the endograft within the aorta and subsequent exclusion of the aneurysmal component.

The term endoleak is specific to EVAR, and describes the primary means by which endografts fail. Type I endoleaks occur because of inadequate graft seal proximally or distally, resulting in perigraft flow and aneurysm sac pressurization. Type II endoleaks occur when branch arteries arising from the aneurysmal aorta back-bleed into the aneurysm sac due to collateral flow. Type III endoleaks occur when flow persists between segments of a modular graft. Type IV endoleaks occur when flow persists through endograft material (graft porosity). Type V endoleaks have also been called "endotension", and occur when pressurization of the sac occurs in the absence of any demonstrable endoleak. Type I and Type III endoleaks are most concerning for rupture, although persistent Type II endoleaks can also lead to aneurysm rupture and premature death.

The most common method of EVAR follow-up is computed tomographic angiography (CTA). These studies allow accurate measurement of aneurysm sac diameters and volumes. They also are highly sensitive and specific for endoleaks. Type II endoleaks are treated if they remain persistent and are present in the setting of aneurysm sac enlargement. Type I and III endoleaks are immediately treated when identified. Type IV endoleaks are rarely seen with current endograft technology.