Madigan MC, et al. - Given that 6% to 8% of type II endoleaks are associated with sac enlargement and respond poorly to treatment, researchers investigated if these enlargements are associated with delayed or occult type I and III endoleaks. Retrospectively reviewing patients with interventions for endoleak after endovascular aortic repair from 2000 to 2016, they suggest suspecting a delayed or occult type I or III endoleak in association with failed attempts treating type II endoleaks and/or a rapid aortic sac growth of 5 mm/y or greater. Occult endoleaks were noted to have a correlation with a decreased chance of endoleak resolution.