12.3 Endovascular Aneurysm Repair (EVAR) Surveillance & Endoleaks

The goal of EVAR follow-up

Endovascular aneurysm repair (EVAR) places a fabric-covered stent-graft inside an aneurysm to exclude the sac from direct arterial flow. Follow-up assesses the repair, sac size, limb patency, and complications. A stent-graft can remain patent while the excluded sac is still perfused. Conversely, a stable sac with no visible leak does not eliminate the need for the prescribed long-term surveillance plan.

Review the device, implantation date, prior imaging, known endoleaks, symptoms, and interventions. Identify the main body, proximal seal, modular junctions, iliac limbs, and distal seals. Complex fenestrated or branched repairs require device-specific protocols beyond a routine infrarenal bifurcated graft assessment. Know what the requested examination can adequately visualize.

Complete duplex acquisition

Use grayscale to assess the sac and visible graft configuration, color or power Doppler to search for flow, and spectral Doppler to characterize suspected channels and limb hemodynamics. Measure the maximum residual sac diameter outer wall to outer wall, including thrombus, in reproducible orthogonal planes. Avoid an oblique measurement of a tortuous sac.

Examine the accessible proximal attachment, main body, component overlaps, both limbs, distal attachments, and adjacent inflow/outflow. Record representative velocities and investigate focal acceleration, kinking, or poor distal flow using validated device/segment criteria. A fixed “normal graft PSV” does not apply to every limb size, device, and hemodynamic state.

Search the excluded sac for slow flow

Set the color scale and wall filter low enough to reveal slow flow while controlling motion artifact. Raise gain to the noise threshold, then reduce it slightly. Scan the sac in several planes and watch for communication with a seal zone, component junction, or branch vessel. Power Doppler can help detect slow flow but remains sensitive to motion and insonation conditions. Confirm suspicious color with spectral sampling when feasible.

A displayed velocity scale in cm/s is not the same quantity as PRF in hertz; their relationship depends on frequency and angle assumptions. Do not present 10–20 cm/s as a universally equivalent PRF value. Settings are starting points that must be optimized on the actual system and patient.

Classify by anatomic mechanism

Type Ia involves the proximal seal and Ib a distal seal. Type IIIa involves component separation and IIIb a fabric defect. In commonly used Type II subclassification, IIa has a single communicating branch and IIb multiple branches. The distinction is not “IMA versus lumbar”: one lumbar source can be IIa, and multiple feeding/draining vessels can be IIb. If all branches cannot be demonstrated, report Type II without inventing a subtype.

Location and communication are central to classification. Types I and III may show a brisk pulsatile channel; Type II can have low-velocity or bidirectional flow. Waveform speed or a to-and-fro pattern alone does not reliably establish the type. A leak near a seal must be traced rather than labeled from one PSV threshold.

Sac change and clinical significance

Compare with prior measurements made by a consistent method. Sac regression is reassuring; expansion warrants investigation, including consideration of an occult endoleak. A 5 mm change is commonly used as a meaningful reporting trigger, but measurement error, timeframe, type of leak, guideline, and device influence the response. Do not state that any 5 mm expansion automatically mandates a specific intervention.

Types I and III generally require prompt evaluation and correction because they expose the sac to arterial pressure. A stable Type II leak is often monitored. Persistent Type II flow with sac expansion needs specialist review, further imaging, and consideration of treatment. The treating team determines the intervention threshold and method. Type V is a diagnosis of sac expansion without a demonstrated leak, not proof that flow is impossible to detect with another modality.

Worked cases

A stable sac has a posterior low-velocity channel communicating with a lumbar artery. This supports Type II endoleak. If only one branch is demonstrated, do not call it IIb solely because the branch is lumbar. Continued surveillance may be appropriate when the sac is stable, under the treating clinician's plan.

A second patient has a new jet entering the sac beside the proximal attachment and increasing sac diameter. This is concerning for Type Ia seal failure. Preserve the images and communicate promptly. “Low-risk Type II” would be an unsafe assumption merely because a branch vessel is nearby. Additional imaging may clarify the anatomy before repair.

Surveillance and complementary imaging

The 2022 ACC/AHA guideline recommends baseline CT at about one month after EVAR. If there is no endoleak or sac enlargement, duplex at 12 months and annually thereafter is recommended; concerning findings alter the schedule. A six-month study is not universally mandatory after a normal baseline. Periodic cross-sectional imaging can assess components or complications poorly characterized by duplex.

CT angiography evaluates graft geometry and contrast filling, while contrast-enhanced ultrasound can improve slow-flow detection in suitable settings. MRI may be useful for selected devices and patients. Contrast agents, renal function, radiation, metal artifact, availability, and the specific clinical question affect the choice. Document technically limited regions so that a negative ultrasound is not mistaken for a complete exclusion of every complication.

SVS endoleak overview and 2022 ACC/AHA aortic guideline — checked October 18, 2026.

CIRSE endoleak standards of practice, 2024 — supports mechanism-based classification, including single versus multiple communicating branches.