Anatomical Position of Renal Veins and Optimal IVC Filter Placement
Which Renal Vein is Lower?
The right renal vein is typically lower than the left renal vein, though anatomical variations exist. 1, 2 This anatomical relationship is critical for proper IVC filter positioning, as the filter must be placed below the lowest renal vein to avoid compromising renal venous drainage while still capturing emboli from the lower extremities.
Ideal IVC Filter Position
IVC filters should be placed in the infrarenal IVC, immediately below the lowest renal vein (typically the right renal vein), ideally within 15-20 mm of the most inferior renal vein. 3
Standard Positioning Guidelines
Infrarenal placement is the default position, with the filter apex positioned in the infrarenal portion of the IVC 3
The optimal distance is approximately 3-15 mm below the lowest renal vein, as demonstrated in clinical practice where filters were successfully deployed an average of 3.25 mm below the lowest renal vein 1, 4
Positioning at the L2 vertebral level on plain radiograph typically corresponds to appropriate infrarenal placement 4
Special Circumstances Requiring Suprarenal Placement
Suprarenal filter placement may be indicated when thrombus is identified in the renal veins or infrarenal IVC. 3
Specific indications for suprarenal placement include:
Presence of thrombus in the infrarenal IVC or renal veins requires filter placement above the renal veins to prevent embolization 3
Renal cell carcinoma with tumor thrombus extending into the renal vein or IVC may necessitate suprarenal filter placement prior to therapeutic interventions like transcatheter arterial embolization 5
Pregnancy considerations: In pregnant patients, suprarenal placement may be preferred to avoid compression from the gravid uterus, though this must be balanced against increased technical difficulty 3
Technical Considerations for Accurate Placement
Pre-procedural imaging with CT or intravascular ultrasound (IVUS) significantly improves placement accuracy and identifies anatomical variations. 1, 2
Key technical points include:
CT scan measurements correlate closely with IVUS measurements for determining the distance from the right atrium to the lowest renal vein and iliac confluence 2
Anatomical variations occur in approximately 12-13% of patients, including duplicated renal veins, circumaortic left renal veins, or retroaortic left renal veins, all of which can be identified on pre-procedural imaging 1, 2
IVUS-guided bedside placement allows accurate filter deployment within 15 mm of the most inferior renal vein without contrast venography or fluoroscopy 4
The IVC diameter typically ranges from 18-28 mm, which should be measured pre-procedurally to ensure appropriate filter selection 4
Common Pitfalls to Avoid
Malposition is a significant risk that can be minimized with proper pre-procedural planning:
Failure to identify the lowest renal vein can result in suprarenal placement, potentially compromising renal venous drainage 1, 2
Placement too far caudal (>20 mm below the renal veins) may theoretically increase thrombosis risk, though clinical data show no statistically significant difference in outcomes 6
Missing anatomical variations such as duplicated or circumaortic renal veins can lead to inadvertent suprarenal placement or inadequate protection 1, 2
In pediatric patients, the catheter tip of a femoral catheter should lie above the renal veins at the first lumbar vertebra level to ensure proper positioning 3
Verification of Placement
Post-deployment imaging should confirm appropriate filter position:
Plain abdominal radiographs can verify filter location relative to vertebral landmarks, with L2 level typically indicating infrarenal placement 4
Post-deployment venography or IVUS confirms no strut malposition and appropriate relationship to the renal veins 1, 4
Color-flow duplex ultrasound of the femoral veins should be performed to rule out access site thrombosis 4