Endovascular aneurysm repair (EVAR) has transformed the treatment of abdominal aortic aneurysms, but it introduces a unique follow-up concern: the possibility of an endoleak, in which blood continues to flow into the aneurysm sac despite the stent graft being in place. Type II endoleaks, the most common type encountered after EVAR, are generally caused by retrograde flow through side branch vessels such as lumbar arteries or the inferior mesenteric artery, and embolization has become a primary tool for addressing them when treatment is indicated.
What Is a Type II Endoleak, and Why Does It Occur?
A type II endoleak occurs when small branch vessels that were not directly sealed by the stent graft continue to supply blood into the aneurysm sac in a retrograde (backward) direction, essentially bypassing the graft's intended exclusion of the aneurysm. Common source vessels include lumbar arteries and the inferior mesenteric artery, both of which can maintain collateral connections to the sac even after the main aortic flow has been redirected through the graft. This type of endoleak is generally the most frequently identified endoleak type on post-EVAR surveillance imaging.
Why Do Some Type II Endoleaks Require Treatment While Others Do Not?
Not every type II endoleak requires intervention. Many resolve spontaneously over time as the feeding vessels naturally thrombose, and some persist without causing sac growth, in which case they may simply be monitored with continued imaging surveillance. Treatment is generally considered when a type II endoleak is associated with ongoing aneurysm sac growth on serial imaging, since sac enlargement suggests the leak is generating enough pressure within the sac to pose an ongoing risk. This distinction — leak alone versus leak with sac growth — is a key factor a qualified physician uses to decide whether embolization is warranted.
How Does Sac Embolization Work?
When treatment is indicated, sac embolization involves accessing the aneurysm sac itself, often through a translumbar approach (a needle passed directly through the back into the sac under imaging guidance) or through a transarterial catheter-based route navigating through collateral vessels to reach the sac. Once access to the sac is established, embolic material is deployed to occlude both the feeding vessels and, in many techniques, the sac cavity itself, with the goal of eliminating the pressure-generating blood flow contributing to the endoleak.
What Does the Translumbar Approach Involve?
The translumbar approach is a technique in which a needle is advanced directly through the back, guided by CT or fluoroscopic imaging, into the aneurysm sac, bypassing the need to navigate through the arterial tree via collateral vessels. This route can be advantageous when the feeding vessels are difficult to access from within the arterial system, offering a more direct path to deliver embolic material into the sac itself. The choice between a translumbar and transarterial approach depends on individual anatomy and is determined by the treating interventional radiologist.
What Does Follow-Up Look Like After Sac Embolization?
Following embolization for a type II endoleak, patients continue with the same surveillance imaging schedule generally recommended after any EVAR procedure, monitoring for sac size stability and confirming resolution or persistence of the endoleak. Some patients require repeat treatment if the endoleak recurs or if sac growth continues despite initial embolization, since collateral vessels can sometimes recanalize or new feeding vessels can be identified over time.
Embolic Devices for Endoleak Management
Type II endoleak embolization relies on embolic devices capable of achieving durable occlusion of variable-sized feeding vessels and, in some techniques, the sac cavity itself. INVAMED manufactures the MultiBEAM Embolization Plug, a self-expanding occlusion device with manufacturer-reported indications that include endoleak treatment; further details are available on the MultiBEAM Embolization Plug product page. Availability and indications vary by country, and the Instructions for Use (IFU) should always be consulted.
Device availability and regulatory status vary by country. Please contact INVAMED or your authorized local distributor for current regulatory information applicable to your region.