With the advent of retrievable filters there is renewed popularity for temporary caval interruption. To our knowledge, no one has yet to follow the population of intended temporary caval interruption, who undergo failed retrieval, and consequently end up with a permanent IVC filter. This study will look at the incidence and degree of caval occlusion, caval stenosis and incidence of DVT in patients at The Alfred who have had a failed retrieval of an implanted IVC filter. Patient will be recruited for up to four years, the incidence of failed retrieval at The Alfred is 10 per year, and follow up will be ongoing.