Endoleak is persistent blood flow in the space between the stent-graft and the aneurysm sac after endovascular aortic repair (EVAR or TEVAR). It is the most common complication after EVAR (15-30% incidence). Five types exist: Type I — leak from graft attachment site (proximal Ia, distal Ib), high-pressure requiring emergent intervention; Type II — retrograde filling via lumbar arteries or inferior mesenteric artery (IMA) (most common, 20-25%), most resolve spontaneously; Type III — graft modular disconnection or graft defect, high-pressure; Type IV — graft porosity (rare in current generation grafts); Type V (endotension) — sac expansion without detectable contrast filling. CTA (arterial + delayed phase) is the gold standard for diagnosis; contrast accumulation outside the graft within the aneurysm sac is the main finding. Contrast filling timing (arterial vs delayed phase) is critical for determining endoleak type.
Age Range
60-90
Peak Age
72
Gender
Male predominant
Prevalence
Uncommon
Endoleak represents failure to achieve the fundamental goal of EVAR — isolation of the aneurysm sac from systemic pressure. In successful EVAR, the stent-graft is deployed within the aneurysm lumen and seals to the aortic wall at proximal/distal attachment sites (landing zones) through radial force → the aneurysm sac is isolated from systemic pressure → the sac thromboses and gradually shrinks. In Type I endoleak, inadequate graft-to-wall seal (due to aortic neck angulation, calcification, short neck) allows high-pressure arterial blood to leak from the attachment site → the sac continues to be pressurized at systemic levels → rupture risk persists. In Type II endoleak, low-pressure retrograde flow through lumbar arteries or IMA fills the sac — these branches, normally perfused by the aorta, develop retrograde collateral flow after EVAR. On CTA, Types I and III fill in the early arterial phase (high pressure, direct aortic flow) while Type II typically fills in the delayed phase (low pressure, collateral flow). This timing difference is a critical diagnostic clue for determining endoleak type and thus treatment urgency. Aneurysm sac size is the most important parameter in follow-up — sac growth indicates clinically significant endoleak requiring intervention.
Contrast accumulation outside the graft within the aneurysm sac on CTA is the defining finding of endoleak. Contrast filling timing is critical for type determination and treatment decision: arterial phase filling → high-pressure (Type I/III, emergent intervention); delayed phase filling → low-pressure (Type II, mostly conservative).
Contrast leakage from the proximal (Type Ia) or distal (Type Ib) graft attachment site into the aneurysm sac on arterial phase CTA. Contrast leaks directly from the aortic lumen — this is high-pressure flow and the sac immediately fills at systemic pressure. Contrast filling is linear or jet-like in pattern, extending from the attachment site into the sac. Most dangerous endoleak type — rupture risk persists and emergent reintervention is required.
Report Sentence
Arterial phase contrast leakage from the proximal/distal graft attachment site into the aneurysm sac, consistent with Type I endoleak; emergent reintervention is indicated.
Contrast accumulation outside the graft within the aneurysm sac on delayed phase CTA (60-120 seconds) — no or minimal filling on arterial phase. Contrast filling focus is located near the lumbar artery or IMA origin. Most common endoleak type (60-80%). Most Type II endoleaks are asymptomatic and resolve spontaneously. If no sac size increase, conservative follow-up is sufficient; if sac grows, translumbar embolization or laparoscopic ligation is required.
Report Sentence
Delayed phase contrast accumulation outside the graft within the aneurysm sac, consistent with Type II endoleak; sac size monitoring is recommended.
Contrast leakage from a defect in the graft body or at the junction of modular components on arterial phase CTA. Contrast passes directly from the graft lumen through a defect in the graft wall or modular disconnection point into the aneurysm sac. High-pressure endoleak like Type I. Develops from graft aging, mechanical fatigue, or modular component migration. Requires emergent reintervention — typically additional stent-graft placement at the defect site.
Report Sentence
Arterial phase contrast leakage from defect in graft body/modular junction, consistent with Type III endoleak; emergent reintervention is required.
Aneurysm sac diameter increase (>5 mm) on serial CTA follow-up without detectable contrast filling — endotension (Type V endoleak). Sac pressure increases but contrast leakage cannot be demonstrated on conventional imaging. Possible mechanisms: very slow flow endoleak (below CTA temporal resolution), pressure transmission through thrombus, fluid passage through ultrafiltration. If sac growth continues, intervention is required.
Report Sentence
Aneurysm sac diameter increase of __ mm on serial follow-up without identifiable endoleak focus; should be evaluated for endotension (Type V endoleak).
Flow signal outside the graft within the aneurysm sac on contrast-enhanced ultrasound (CEUS) or color Doppler US. CEUS has increasingly used as an alternative to CTA for endoleak diagnosis and follow-up — microbubble contrast (SonoVue) demonstrates intrasac contrast accumulation in real-time. The advantage of CEUS over CTA is no radiation or iodinated contrast requirement. Sensitivity approaches CTA, particularly effective for Type II endoleak detection.
Report Sentence
Contrast accumulation outside the graft within the aneurysm sac on CEUS, consistent with endoleak.
Enhancement within the aneurysm sac on delayed phase contrast-enhanced MRA (gadolinium-based contrast). MRA is used as an alternative in patients with iodinated contrast contraindication or when endoleak is not detected on CTA. The T1 shortening effect of gadolinium-based contrast causes the endoleak focus to show hyperintense signal on T1-weighted sequences. Non-contrast MRA (time-of-flight) may be insufficient for low-flow endoleak.
Report Sentence
Enhancement within the aneurysm sac on delayed phase contrast-enhanced MRA, consistent with endoleak.
Criteria
Contrast leakage from proximal (Ia) or distal (Ib) graft attachment site. Arterial phase filling. High-pressure.
Distinct Features
Most dangerous type — sac fills at systemic pressure, rupture risk persists. Requires emergent reintervention (graft extension, proximal cuff, or conversion).
Criteria
Sac filling through retrograde collateral flow via lumbar arteries or IMA. Delayed phase filling. Low-pressure.
Distinct Features
Most common endoleak type (60-80%). Most resolve spontaneously. Conservative follow-up if sac stable or shrinking. Translumbar embolization for sac growth.
Criteria
Defect in graft body or modular component disconnection. Arterial phase filling. High-pressure.
Distinct Features
Dangerous like Type I. Results from graft mechanical fatigue or migration. Emergent reintervention — additional graft placement at defect site.
Criteria
Sac size increase without detectable contrast filling. Sac pressure increased but endoleak not demonstrable on conventional CTA.
Distinct Features
DECT iodine map or CEUS may reveal occult endoleak. If sac growth continues, re-lining or conversion may be needed.
Distinguishing Feature
In rupture, contrast exits beyond the sac (into retroperitoneal space); in endoleak, contrast remains within the sac. Retroperitoneal hematoma present in rupture, absent in endoleak.
Distinguishing Feature
In AEF, periaortic gas, loss of fat plane with bowel, and contrast leakage into bowel lumen are present. In endoleak, no gas or bowel communication.
Distinguishing Feature
In untreated AAA, no graft present — intrasac contrast filling entirely reflects lumen patency. Post-EVAR endoleak shows separate contrast accumulation around the graft, which is pathognomonic.
Distinguishing Feature
In mycotic aneurysm, no stent-graft present, periaortic inflammatory changes and saccular aneurysm exist. Endoleak only occurs post-EVAR.
Urgency
urgentManagement
interventionalBiopsy
Not NeededFollow-up
3-monthEndoleak management varies by type: Types I and III are high-pressure and require emergent reintervention (graft extension, proximal/distal cuff, or open conversion). Type II is most common and most can be conservatively observed — if sac size stable or shrinking, CTA follow-up every 6-12 months is sufficient; if sac grows >5 mm, translumbar embolization or laparoscopic ligation is performed. Type V (endotension) requires intervention if sac growth continues. Standard post-EVAR follow-up protocol: CTA at 1 month, 6 months, 12 months, then annually. If no endoleak and sac stable/shrinking, transition to radiation-free US or CEUS follow-up protocol is possible.
Type I and III endoleaks require urgent intervention (graft extension or revision). Type II is most common and most resolve spontaneously; embolization is performed if sac growth accompanies. Type V (endotension) is rare and its mechanism is not fully understood. Lifelong CT surveillance is required after EVAR (1, 6, 12 months, then annually).