Interventional Radiology · Aortic interventions · Contemporary classification

Endoleak Types I–V

Classification of persistent aneurysm-sac perfusion or pressurisation following endovascular aortic repair, based on the underlying source.

Purpose

To identify the mechanism of aneurysm-sac perfusion or expansion after EVAR or TEVAR and guide the urgency and type of management.

Type	Mechanism	Source or subtype	Key implication
I — Attachment-site leak	Failure of the endograft to seal against the vessel wall	IA: proximal attachment site; IB: distal attachment site; IC: around an iliac occluder	Direct systemic-pressure communication; prompt correction is generally required
II — Branch-vessel endoleak	Retrograde flow from patent aortic or iliac side branches into the aneurysm sac	Common sources include lumbar arteries and the inferior mesenteric artery	Usually observed unless persistent and associated with clinically significant sac expansion
III — Endograft failure	Loss of integrity between or through endograft components	IIIA: modular component separation; IIIB: fabric disruption or tear	Direct systemic-pressure communication; prompt correction is generally required
IV — Graft porosity	Blood passage through otherwise intact porous graft fabric	Typically detected during or shortly after endograft deployment	Usually transient and uncommon with contemporary devices
V — Endotension	Aneurysm-sac expansion without a demonstrable endoleak on available imaging	No visible source of sac perfusion	Diagnosis of exclusion; investigate for an occult Type I, II or III endoleak

How to use it

Types I and III directly expose the aneurysm sac to systemic arterial pressure and are considered high-risk endoleaks.
Type II is the most frequent endoleak and results from retrograde collateral-vessel flow rather than failure of an attachment site.
Type IV represents graft-fabric porosity and is principally an early post-deployment phenomenon.
Type V describes progressive sac enlargement without a visible endoleak and should prompt a search for an occult leak using appropriate multiphasic or problem-solving imaging.

Common mistake

Do not label every peripheral sac-enhancement focus as Type II: enhancement adjacent to a proximal or distal seal zone or between graft components must raise concern for a higher-pressure Type I or III endoleak.

Exam pearl

Remember the mechanism sequence: seal failure, side branches, structural failure, porosity and endotension correspond to Types I–V.

Viva questions

What is an endoleak?: An endoleak is persistent blood flow outside the endograft lumen but within the treated aneurysm sac or adjacent excluded vascular segment after endovascular aortic repair.
Enumerate the five types of endoleak.: Type I is attachment-site seal failure, Type II is retrograde branch-vessel flow, Type III is structural endograft failure, Type IV is graft porosity and Type V is sac expansion without a visible leak, termed endotension.
What are the subtypes of a Type I endoleak?: Type IA arises at the proximal attachment site, Type IB at the distal attachment site and Type IC around an iliac occluder.
What are the usual sources of a Type II endoleak?: It usually results from retrograde flow through patent lumbar arteries or the inferior mesenteric artery; other collateral branches may also contribute.
Differentiate Type IIIA from Type IIIB endoleak.: Type IIIA is caused by separation or inadequate overlap of modular endograft components, whereas Type IIIB results from disruption or tearing of the graft fabric.
Which endoleak types generally require prompt treatment?: Types I and III generally require prompt correction because they provide direct systemic-pressure communication with the aneurysm sac and increase the risk of sac expansion and rupture.
What is a Type V endoleak?: Type V endoleak, or endotension, is progressive aneurysm-sac expansion without a demonstrable endoleak on available imaging. It is a diagnosis of exclusion after searching for an occult Type I, II or III leak.
What is the major imaging pitfall when diagnosing a Type II endoleak?: A low-flow Type I or III endoleak may mimic or coexist with a Type II leak. The seal zones and component junctions must therefore be assessed carefully, particularly when the aneurysm sac is enlarging.