Repeated detection of gas in the portal vein after liver transplantation: A sign of EBV-associated post-transplant lymphoproliferation?

A 1-yr-old child presented with intractable right sided pleural effusion and progressive clinical deterioration 3 weeks after liver transplantation for Alagille Syndrome. He had been treated successfully for severe acute rejection before. Ultrasound and Doppler mode studies repeatedly demonstrated air in the portal vein.