The use of iodinated contrast in the critically ill trauma patient has been associated with the development of acute renal failure. The low incidence of nephrotoxicity associated with carbon dioxide (CO₂) makes it an ideal contrast agent for cavography. However, the use of CO₂ has been limited, because reportedly it underestimates the diameter of the inferior vena cava (IVC).

During a 6-month period (January 2000 through June 2000), 25 adult trauma patients required IVC filter placement. Bedside cavagrams using CO₂ followed by iodinated contrast were employed to determine the diameter of the IVC and the anatomy of the renal veins.

Using CO₂ injection for cavography, we were able to determine the diameter of the IVC and the anatomy of the renal veins in all patients. Furthermore, when CO₂ cavography was compared with the results obtained with iodinated contrast, the difference in diameter of the IVC was within 1 mm.

Based on these data, it was determined that CO₂ cavagrams accurately reflect the diameter of the IVC and the anatomy of the renal veins. Additionally, CO₂ cavagrams can be safely performed in the intensive care unit during bedside placement of IVC filters.