Where in the IVC should the filter be placed, and why?
It is preferable that the filter be placed immediately below the lowest renal vein. With the apex of the filter sitting just below the renal veins, any clot caught by the filter is subject to high blood flow from the renal veins and may be more likely to lyse. Theoretically, this may help maintain caval patency over the lifetime of the patient. Placement below the renal veins also decreases the risk of renal vein thrombosis if the filter is subject to a large clot burden. Suprarenal IVC filters are relatively safe but have a theoretic increased risk of renal vein thrombosis and should be reserved for instances in which there is thrombus in the infrarenal IVC.