Contrast-Enhanced Ultrasound and CT Fusion Imaging in EVAR Follow-Up: Diagnostic Workflow, Endoleak Detection, and Imaging Pitfalls

Endovascular aneurysm repair (EVAR) has become a widely adopted treatment for abdominal aortic aneurysms, offering lower perioperative morbidity and mortality than open surgical repair. Nevertheless, long-term imaging surveillance remains essential because procedure-related complications may occur years after treatment. Among these, endoleaks represent the most frequent and clinically relevant finding, particularly Type II endoleaks, which are sustained by retrograde collateral perfusion and may be associated with persistent aneurysm sac filling and sac enlargement. Computed tomography angiography (CTA) remains the reference standard for anatomical assessment after EVAR, providing detailed evaluation of endograft integrity, aneurysm sac morphology, and vascular anatomy. However, repeated CTA examinations involve cumulative radiation exposure and iodinated contrast administration and may be limited in the detection of low-flow or intermittent endoleaks. Contrast-enhanced ultrasound (CEUS) provides real-time hemodynamic assessment, improves detection of slow-flow endoleaks, and avoids both ionizing radiation and nephrotoxic contrast agents. Nevertheless, CEUS may be affected by operator dependency and limited anatomical overview. CT–ultrasound fusion imaging combines pre-acquired CTA datasets with real-time ultrasound through spatial co-registration and probe tracking, enabling simultaneous evaluation of vascular anatomy and flow dynamics. This narrative review critically synthesizes current evidence regarding CTA, CEUS, and CT–ultrasound fusion imaging in post-EVAR surveillance, with particular emphasis on the incremental clinical value of fusion imaging beyond standalone CTA and CEUS. Particular attention is devoted to diagnostic performance, technical implementation, clinical applicability, current limitations, and future perspectives of CT–CEUS fusion imaging.