Air embolism: a potential complication of retrograde pyelography.

We report 2 cases of venous air embolism as a complication of retrograde pyelography. The pyelovenous route of embolization was documented radiographically. The mechanisms of pyelovenous backflow are reviewed and the clinical implications of this phenomenon are discussed. Pyelovenous backflow may provide the mechanism for air embolism when gas is present in the urinary tract.