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An endoleak is a persistent blood flow outside the lumen of the endovascular graft but within the aneurysm sac after endovascular aneurysm repair (EVAR). It is the most common complication following EVAR and can compromise aneurysm exclusion, risking continued sac pressurization and rupture.

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https://www.youtube.com/watch?v=EgMYmonFNOw

Classification

Type	Mechanism	Source of Leak	Clinical Relevance
Type I	Inadequate seal at graft ends	Ia: proximal attachment site Ib: distal attachment site	High rupture risk – requires urgent repair
Type II	Retrograde flow from branch vessels	Lumbar arteries, IMA, intercostals	Most common, often benign, but may enlarge sac
Type III	Structural failure of graft	IIIa: Modular disconnection IIIb: Fabric tear	High rupture risk, needs repair
Type IV	Graft porosity (rare with modern devices)	Transgraft flow due to fabric permeability	Usually self-limited
Type V	Endotension – sac expansion with no visible leak	Unknown	Diagnosis of exclusion, may need reintervention

![Classification of endoleaks

Czerny M, Grabenwöger M, Berger T, et al. EACTS/STS Guidelines for Diagnosing and Treating Acute and Chronic Syndromes of the Aortic Organ. The Annals of Thoracic Surgery. 2024;118(1):5-115. doi:https://doi.org/10.1016/j.athoracsur.2024.01.021](attachment:ec930ae3-6cae-417d-8cd9-eeb8f0704d8a:gr32_lrg.jpg)

Classification of endoleaks

Radiology

CT Angiography (CTA) – Modality of Choice:

Arterial and delayed phase imaging is crucial
Use MPR and 3D reconstructions for component integrity and sac size

Type	CTA Findings
I	Contrast adjacent to graft ends; no thrombus at sealing zones
II	Delayed sac opacification (especially posteriorly); lumbar or IMA seen enhancing
III	Contrast between stent components or graft disruption
IV	Diffuse enhancement of sac in early post-op scans
V	Sac enlargement without visible leak or enhancement

Key CT Criteria for Intervention:

Sac growth >5 mm
Persistent type I/III leak
New onset leak after prior stable scans

Management

Management by Endoleak Type:

Type	Management Approach
Type I	Urgent endovascular or surgical repair – e.g., cuffs, extension grafts
Type II	- Observe if sac stable or shrinking - Embolization (via transarterial or translumbar route) if sac enlarges
Type III	Endovascular repair – replace component, bridging stent
Type IV	No specific treatment; resolve spontaneously
Type V	Controversial; may need graft relining or conversion to open repair