Endoleak After EVAR: What It Means When You Are Told Your Aneurysm Is "Leaking"
An endoleak is the commonest finding on scans after a stent-graft repair, and the word frightens almost everyone who hears it. Most are not emergencies. This guide explains the five types, which ones matter, how they are watched and how they are fixed.
After endovascular aneurysm repair (EVAR), the aneurysm is not removed. A fabric-covered stent-graft is placed inside it so that blood flows through the graft and the aneurysm sac around it is excluded from pressure and should slowly shrink. An endoleak means that some blood is still reaching the sac outside the graft. It does not mean the graft has torn or that blood is escaping from the body, and it is not the same as a rupture. It is, however, the main reason EVAR needs lifelong imaging surveillance, because an untreated endoleak that keeps the sac pressurised can allow it to grow and, eventually, to rupture.
Endoleaks are common. Depending on the device and the anatomy, roughly one in five to one in four people will have one at some point after EVAR. Most are found on routine scans in people who feel perfectly well, and a large proportion are of the low-pressure type that is simply watched.
What an endoleak is, and is not
Think of the stent-graft as a new inner pipe inside an old, enlarged one. The repair works when the new pipe seals tightly against healthy artery at both ends and all the blood travels inside it. An endoleak is any route by which blood still gets into the space between the two pipes. Where that blood comes from determines the type, how much pressure it transmits to the sac, and how urgently it needs attention.
An endoleak is not a leak out of the aorta into the abdomen. It is not usually something you can feel. And finding one on a scan does not by itself mean the operation has failed; many sacs with a small endoleak remain stable for years.
The five types and what each means
| Type | Where the blood comes from | Pressure on the sac | Usual approach |
|---|---|---|---|
| Type I | A gap at a sealing zone: at the top of the graft below the kidney arteries (Ia) or at the bottom in the iliac arteries (Ib) | High: direct arterial pressure | Treated promptly, usually with an extension cuff or stent, sometimes with anchoring devices or a more complex graft |
| Type II | Backflow from small branch arteries (lumbar arteries, inferior mesenteric artery) that still open into the sac | Low | Watched. Treated only if the sac grows (commonly 5 mm or more) despite surveillance |
| Type III | A gap between graft components, or a tear in the fabric | High | Treated promptly by relining the junction or the damaged segment |
| Type IV | Blood seeping through the pores of the graft fabric itself | Minimal; seen mainly on the day of surgery with modern grafts, and self-limiting | No treatment |
| Type V (endotension) | No visible leak, but the sac keeps enlarging | Presumed raised | Investigated for a hidden type I, II or III leak; treated if the sac continues to grow |
In practice the first question your surgeon asks is whether the leak is high-pressure (type I or III) or low-pressure (type II). High-pressure leaks put the sac at the same risk as an untreated aneurysm and are fixed. Low-pressure leaks are a nuisance rather than a danger unless the sac is growing.
How endoleaks are found
Endoleaks are almost always picked up on surveillance imaging rather than through symptoms. The scan used depends on the stage and on the patient:
- CT angiography at about one month after EVAR, and whenever a problem is suspected: it shows the graft, the sac diameter and the leak, and in a delayed phase can tell a slow type II leak from a type I.
- Duplex ultrasound, sometimes with contrast agent, for routine yearly checks in stable patients, because it avoids radiation and contrast dye and is very good at measuring sac size and detecting flow in the sac.
- Plain X-ray to check the metal frame of the graft for kinks, fractures or movement.
- Angiography in the operating theatre when a leak is to be treated, to define its exact source.
The key measurement is not the leak itself but the sac diameter over time. A sac that is shrinking or stable is behaving well regardless of a small leak. A sac that is growing needs an explanation and usually a plan.
Watch: EVAR: Repairing an Aortic Aneurysm from Within · Read: EVAR for aortic aneurysms in Singapore
Which endoleaks are watched and which are treated
Type I and type III leaks are treated, usually soon after they are found, because they expose the sac to full arterial pressure. Occasionally a small type Ia leak seen on the operating table is left for a few weeks to see whether it seals as the graft settles, but a persistent one is fixed.
Type II leaks are watched. International guidelines, including the ESVS 2024 guideline on abdominal aortic aneurysm, recommend treating a type II endoleak only when it is associated with sac enlargement, most commonly defined as growth of 5 mm or more, or 10 mm from the smallest post-operative size. Up to half of type II leaks seal on their own within the first year, and most of those that persist do not cause the sac to grow. Treating every type II leak would mean many unnecessary procedures.
Type V (endotension) prompts a more careful search, often with a different imaging technique, because the "no visible leak" label frequently hides a small type I or III leak that was missed. Continued growth without any identifiable source is usually treated by relining or converting the repair.
How endoleaks are treated
Most endoleak treatment is itself endovascular, done through the groin arteries under local or general anaesthetic, with a short hospital stay:
- Proximal or distal extension – a short additional cuff or limb to lengthen the seal for a type Ia or Ib leak.
- Endoanchors – small screws placed through the graft into the aortic wall to improve a marginal proximal seal.
- Relining – placing a new graft or bridging stent inside the existing one to cover a type III junction leak or fabric defect.
- Embolisation – for a type II leak with sac growth, the feeding branch or the sac itself is filled with coils, glue or other agents, reached either through the arteries (transarterial) or by a needle passed directly into the sac through the back or abdomen (translumbar or transabdominal).
- Fenestrated or branched conversion – when the seal has failed because the neck has dilated or the graft has slipped, a fenestrated or branched device may be used to land in healthy aorta higher up.
- Open conversion – removing part or all of the stent-graft and performing an open repair. This is uncommon and reserved for leaks that cannot be controlled by other means, graft infection, or rupture.
Choosing between these depends on the type of leak, the anatomy, and fitness. A surgeon who performs the full range, including open conversion, can match the solution to the problem rather than the problem to the available tool.
Sac growth without a visible leak
Endotension is uncomfortable territory for patients and surgeons alike: the sac is growing, the risk is presumed to be rising, but nothing shows on the scan. In most cases a leak is eventually found with better imaging (delayed-phase CT, contrast ultrasound or a diagnostic angiogram). Where it is not, the decision to intervene is based on the rate of growth and the overall size, weighed against the person's fitness and wishes. This is exactly the situation in which a second opinion is worth having.
Had an EVAR elsewhere and lost touch with follow-up?
It happens more often than people expect: the operation went well, the first scans were fine, life moved on and the yearly appointments lapsed. If you had a stent-graft repair in Singapore or overseas and have not had a scan in more than a year, the right step is simply to restart surveillance. Dr Choong reviews previous operation notes and imaging, arranges an up-to-date CT or duplex scan, and sets a follow-up plan. If an endoleak or sac growth is found, the options above are discussed in plain terms. Bring the device details and any previous scans if you have them; if you do not, the review can still begin. Contact Andrew Choong Vascular Surgery at Mount Elizabeth Novena Specialist Centre, or read more on aortic stent surveillance.
Sudden severe abdominal, back or flank pain, collapse or fainting in someone with a stent-graft is treated as a rupture until proven otherwise: call 995 in Singapore or go to the nearest emergency department.
Common questions about endoleaks
My report says I have an endoleak. Is my aneurysm leaking?
Not in the sense most people fear. The blood is still inside the aneurysm sac, not outside the aorta. What matters is the type of leak and whether the sac is growing. A type II leak with a stable or shrinking sac is a common and generally benign finding; a type I or III leak needs treatment but is usually fixed with a short keyhole procedure.
Is an endoleak an emergency?
Rarely. Endoleaks found on routine scans in people who feel well are planned problems, not emergencies. The emergency is rupture, which announces itself with sudden severe pain or collapse. That is why surveillance matters: it finds and fixes the leaks that could lead there.
Can an endoleak go away on its own?
Type II leaks often do: a large proportion seal spontaneously within the first year as the branch arteries clot off. Type I and III leaks do not reliably seal and are treated.
Will I need another operation?
Across all patients after EVAR, roughly one in five needs some further procedure within ten years, most of them minor and endovascular, and most for an endoleak. Having an endoleak therefore raises that likelihood, but a type II leak with a stable sac may never need anything beyond scans.
Can I avoid endoleaks by having open surgery instead?
Open repair does not have endoleaks, which is one of its advantages for younger, fit patients. The trade-off is a much bigger operation and recovery. Our guide to EVAR versus open repair sets out how that decision is made.
How often will I be scanned if I have a type II endoleak?
Usually every six months until the sac is shown to be stable, then yearly. The interval is adjusted to what the scans show rather than fixed for life.