How is a vena cavogram performed before IVC filter placement?
A vena cavogram can be performed via access from a jugular vein, femoral vein, or arm vein. A 5-Fr pigtail catheter with radiopaque markers is recommended so that accurate measurements of the IVC can be taken. The tip of the catheter is placed just above the confluence of the iliac veins, and an injection rate is chosen that causes contrast material to flow down the left and right common iliac veins. Identifying both iliac veins excludes the existence of a duplicated IVC, a normal anatomic variant that alters filter placement. Patients should perform a Valsalva maneuver to distend the IVC maximally during the contrast material injection so that the caval diameter can be accurately measured, preventing caval migration. A radiopaque ruler can be placed underneath the patient to be used as a landmark to facilitate accurate filter placement.