Shown above is a type II endoleak.

An endoleak is characterised by persistent blood flow within the aneurysm sac following endovascular aneurysm repair (EVAR). Normally the aortic stent-graft used in EVAR excludes the aneurysm from the circulation by providing a conduit for blood to bypass the sac.
Endoleak is a common complication of EVAR found in up to 40% of patients. It is seen on CTA, MRA and DSA as contrast opacification of the aneurysm sac outside the graft. Flow in the sac may also be detected on ultrasound. When an endoleak occurs, flow within the aneurysm sac is at systemic or near-systemic pressure. If untreated, the aneurysm may expand and is at risk of rupture. Aneurysm expansion following EVAR always warrants investigation for endoleak.

There are several causes of endoleak which are classified into 5 types as follows:
Type I – leak at graft attachment attachment site.
Type II – aneurysm sac filling via branch vessel (most common).
Type III – leak through defect in graft.
Type IV – leak through graft fabric as a result of graft porosity.
Type V – continued expansion of aneurysm sac without demonstrable leak on imaging (endotension).
Types II and IV usually resolve spontaneously. Type I and III do not, and require immediate treatment. Endoleak may become evident intra-operatively, or months or years later. Therefore life-long imaging surveillance is necessary, usually performed with CTA.

1. Rosen RJ & Green RM. Endoleak Management following Endovascular Aneurysm Repair, Journal of Vascular and Interventional Radiology, 2008;19:S37-S43
2. Kaufman J & Lee M, Vascular & Interventional Radiology The Requisites, Mosby 2004

Credit: Dr Donna D’Souza