Figure 15b. Posttransplantation lymphoproliferative disease. (a) Transverse US image shows a large, heterogeneous, echogenic mass (arrows) that effaces and displaces the porta hepatis. Biopsy demonstrated posttransplantation lymphoproliferative disease. (b) Contrast-enhanced CT image obtained at a different level shows the mass (arrows), which encases the vasculature at the porta hepatis.