Report the filter type and position relative to the renal veins, then tilt, strut penetration through the IVC wall into adjacent organs, fracture and embolised fragments, and caval thrombosis — the findings that decide retrieval.
Orient first
- Filters are ideally infrarenal with the apex below the lowest renal vein.
- Tilt > 15° (verify) makes retrieval harder; strut penetration > 3 mm beyond the wall is common and usually asymptomatic.
- Retrievable filters should be removed when no longer needed.
Acquire the study
- CT venography with a delayed venous phase (~90–120 s).
The manoeuvre
- Axial and coronal reformats: struts beyond the caval wall in mm; into duodenum, aorta, spine, ureter.
- Venous phase: thrombus within or above the filter; caval occlusion.
- Renal vein position relative to the filter apex.
What confirms it
- Position and complications documented on radiograph and CT.
What licenses you to exclude it
- A well-positioned filter without penetration, fracture or thrombus is uncomplicated.
The classic misread
- Calling mixing of unopacified blood thrombus on an early phase.