What nuclear medicine physicians need to know about normal variant left renal vein and IVC anatomy when interpreting whole body PET/CT and their implications

Learning Objectives 1. Describe normal variant left renal vein and IVC anatomy. 2. Familiarize interpreting physicians with the implications certain left renal vein and IVC variants have on future IVC filter placement and why it is important to include these findings in our oncologic PET/CT reports.

Malignancy confers an increased risk for hypercoagulable state, therefore oncologic patients have an inherent increased risk for developing DVT and PE. IVC filter placement in these patients may be required. Most commonly, individuals have a single left renal vein anterior to the aorta, which empties into the IVC at the same level as the right renal vein, and IVC filters are placed just below the ostia for these vessels. The normal variant circumaortic left renal vein can provide a conduit in which lower extremity DVT can bypass an IVC filter and patients who have duplicate IVCs require filters placed in both the right and left IVCs in order to provide adequate protection. These variants are often not appreciated on inferior venacavograms, the most common method for evaluating renal vein and IVC anatomy prior to IVC filter placement. These variants can however be identified on the non-contrast, low dose CT acquired as part of a routine oncologic PET/CT. Reporting these variants may therefore prove useful in alerting referring physicians to their presence and decrease the number of sub-optimally positioned IVC filters