Occult endoleaks revealed during open conversions after endovascular aortic aneurysm repair in a multicenter experience

Background: An occult endoleak (OE) may be the underlying cause of aneurysm sac expansion after endovascular aneurysm repair (EVAR). The aim of this study is to describe intraoperative findings of OE during surgical endograft explantations. Methods: This is a retrospective, multicenter analysis of all open conversions (OC) after EVAR from 1997 to 2020 in 12 vascular centers. We excluded patients with a preoperative diagnosis of endograft infection, endograft thrombosis, and thoracic-EVAR. An OE was defined as an endoleak revealed during OC not shown on preoperative imaging, which was likely the real cause for sac enlargement. We reported the number of OE, and we described the type of OE in relation to the initial alleged or associated endoleak. A separate analysis of patients with an initial diagnosis of endotension was also performed. Results: An OE was found in 32/255 patients (12.5%). In the 78.1% of the cases (25/32) a type II endoleak hid a type I or III endoleak. Endotension was the initial diagnosis of 26/255 patients (10.2%). In 4/26 cases (15.4%), a type I or II OE was revealed. In 5/26 cases (19.2%) an endograft infection was found intraoperatively. In 2/26 cases we found an angiosarcoma. Fifteen cases of endotension (57.7%) remained unexplained. Conclusions: OE represent a not negligible cause of EVAR failure. A type II endoleak associated with sac enlargement may actually conceal a higher-flow endoleak. In most of the cases, the initial diagnosis of endotension remains unexplained. However, endotension sometimes conceals severe underlying pathologies such as infections.