Management of Type II Endoleaks with Ethylene-Vinyl-Alcohol Copolymer Liquid Embolic Agent

Treatment of abdominal aortic aneurysms (AAAs) has evolved significantly during the last two decades, especially with the broader introduction of endovascular aneurysm repair (EVAR) by Parodi et al. in 1991. However, the Achilles’ heel of EVAR remains the endoleak.

Many early type II endoleaks are transient and will resolve spontaneously within 6 months with conservative treatment alone. When a type II endoleak is associated with aneurysm sac enlargement of more than 5 mm, however, treatment of the endoleak is necessary. Different treatment options have been described, including embolization through a transarterial, lumbar (direct puncture), and caval route; laparoscopic ligation; and open surgical repair. Onyx is an embolic agent approved by the U.S. Food and Drug Administration (FDA) for the embolization of arteriovenous malformations in the brain. A similar predecessor compound was first described in the early 1990s by Taki et al. and Terada et al. .

Onyx is an ethylene-vinyl-alcohol copolymer (EVOH) dissolved in dimethyl sulfoxide (DMSO) and suspended micronized tantalum powder (Medtronic, Santa Rosa, California, USA). There are three possible concentrations:

• Onyx LES (liquid embolic system) 18 (6% EVOH)

• Onyx LES 34 (8% EVOH)

• Onyx HD 500 (20% EVOH)

The greater the amount of copolymer, the higher the viscosity. Solidification takes place within 5 minutes after injection.

Preoperative Evaluation

Multislice (1.0-mm) computed tomography angiography (CTA) with arterial and venous phases is performed to define the endoleak anatomically. Inflow from two main sources is responsible for the development and persistence of type II endoleaks:

• 1.

  Flow into the aneurysm sac from the inferior mesenteric artery (IMA) via the Riolan anastomosis and the superior mesenteric artery (SMA)

• 2.

  Lumbar or middle sacral artery inflow originating from the hypogastric artery and via the iliolumbar artery to the feeding branch vessels

Combined inflow from both the IMA and the lumbar vessels can also occur.

Once the location of the vessels feeding and draining a type II endoleak is confirmed, transarterial embolization with Onyx is our preferred approach in Münster, Germany. Fig. 19.1 shows CTA of a patient with type II endoleak originating from the IMA.

When no inflow vessels are detected, or a transarterial attempt fails, a translumbar approach becomes the therapy of choice. Ultimately, if endovascular treatment of a type II endoleak fails, continued aneurysm enlargement dictates a more invasive therapy, such as open surgical repair ( Fig. 19.2 ).