Type IIIb Endoleak Is Not Extremely Rare and May Be Underdiagnosed after Endovascular Aneurysm Repair
To investigate the incidence of type IIIb endoleak associated with the Zenith stentgraft.
A 1.6% incidence of type IIIb endoleak in the Zenith stentgraft is more common than most practitioners may believe. Underdiagnosis and misdiagnosis of type IIIb endoleaks should always be considered in patients with sac expansion.
Fujimura N, Ichihashi S, Matsubara K, Shibutani S, Harada H, Obara H, Kichikawa K, Kitagawa Y. (2019). Type IIIb Endoleak Is Not Extremely Rare and May Be Underdiagnosed after Endovascular Aneurysm Repair. J Vasc Interv Rad, 30:1393-1399. doi:10.1016/j.jvs.2019.03.006
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Retrospective multicenter analysis
Multiple academic centers in Japan
Type IIIa endoleak represents a disconnection of the graft components while type IIIb endoleak is a deterioration of endoprosthesis material leading to aneurysm pressurization. A retrospective review of EVAR using the Zenith stent graft (Cook, Bloomington, Indiana) from 2007-2016 was performed across 11 centers in Japan, identifying 433 patients. A type IIIa endoleak was identified in 0.2% of patients (1/433) and type IIIb endoleak was identified in 1.6% (7/433). Of these seven patients, four had an increase in sac size and five underwent repeat intervention; four of the five repeat interventions patients were diagnosed as type IIIb at the time of reintervention. Three type IIIb endoleaks were from the limb component, three from the main body and one from both.
While type III endoleak was reportedly around 3% for older generation stent grafts, newer third-generation stent grafts were thought to have incidence much lower; the Zenith endograft has previously reported an incidence of 0.4-4.3% however this does not differentiate type IIIa and IIIb. The authors postulate that contrast-enhanced US may aid in the detection of type III endoleaks as it is a dynamic exam whereas CT may result in misdiagnosis.
Type IIIb is an infrequently thought of cause of endoleak post EVAR. This Japanese multicenter study identified a 1.6% incidence of IIIb endoleaks for the Zenith stentgraft; a 1.8% incidence of all type III endoleaks which is within the reported literature range for Zenith stentgrafts. A recent review of the literature by Kwon et al. in J Vasc Surg on type IIIb endoleaks in contemporary EVARs yielded 46 case reports with 35% identified in the main body and 33% at the flow divider; 61% were treated endovascularly. They further conclude that identification of type IIIb endoleak is challenging and the true incidence is not well known.
It is important to keep in mind all types of endoleak during evaluation of sac enlargement. Perhaps dynamic studies such as contrast enhanced ultrasound may play an important role in the future for diagnosis of endoleak type when aneurysm sac expansion is noted on CTA but type of endoleak is not well identified.
Nicole A. Keefe, MD
Fellow, Interventional Radiology
Department of Radiology and Medical Imaging
University of Virginia