Endoleak outflow

A generally accepted anatomic classification for endoleak has been developed over the years [5]. In this system, leaks are defined by their inflow source, regardless of the number and type of other vessels involved in the outflow (Table 14.1). 

Type I endoleak is caused by failure to achieve a circumferential seal at either the proximal (type lA) or distal end (type IB) of the stentgraft. Type IC endoleak is due to non-occluded iliac artery in patients with aorto-mono-iliac stent and femoral-femoral bypass. With type I endoleak, the aneurysm is perfused directly from the aorta or the iliac arteries (inflows). The leak usually communicates through a channel (sometimes multiple channels) with the aneurysmal sac. There are several outflow vessels, mainly lumbar arteries and inferior mesenteric artery (IMA) that communicate with the channel and or the sac (Figs. 14.1,14.2). The pressure within a type I leak is systemic. The tension on the aortic wall remains high. 

Fig. 14.5a,b. Type III endoleak due to a hole in the fabric, a Aortogram demonstrates the endoleak (large black arrow) with IMA (small black arrow) and a lumbar artery (white arrow) acting as an outflow vessel, b The wire is passed through the hole in the aortic aneurysm (arrow)... 

In case of type I endoleak, the origin of the sac is catheterized by placing the catheter between the stentgraft and aortic wall and intra-aneurysmal injection is performed for optimal evaluation of the outflow vessels. 

The occlusion of the iliac artery is usually sufficient to treat the leak. However, in cases of long-term type IC endoleak, many outflow vessels may have developed and the leak may communicate with multiple lumbar arteries and the IMA. These enlarged vessels might be source of late type II endoleak. Thus, we usually embolize both the outflow vessels and the sac before occluding the iliac artery. Another attractive technique to achieve the occlusion of the common iliac artery is to perform an endovascular internal to external iliac artery bypass using stentgraft. This technique can allow the exclusion of the common iliac preserving the internal iliac artery. 

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