In a patient with a history of venous thrombosis, Coumadin should be resumed as soon as the bleeding has stopped. Filters are placed to prevent pulmonary embolism, but do not prevent deep vein thrombosis. In this case the filter may have been tilted allowing a clot from the leg veins to go past the filter into the lungs, the filter may have been in a renal vein, or a clot could have been trapped in the filter and continued to grow on the upstream side of the filter and then broke off, going to the lungs. It is well recognized in the literature that pulmonary embolisms do occur after filter placement. The PREPIC study is the longest duration study showing this. The hospital records will display the size of the filter (it is most likely 30mm). It is not critical to measure the vena cava, since after deployment, the struts expand until they poke into the vena cava wall. Measuring the vena cava takes back seat to making sure the filter is in the vena cava and is properly oriented. Filters have been used to prevent pulmonary embolism for a limited time in patients who cannot be anticoagulated. Prolonged substitution for anticoagulation is not one of the indications for filters. Risks of filters include deep vein thrombosis, clogged filter, migrated filter, and fractures of the filter.