Ultrasonographic evaluation of disturbances in the perfusion of renal graft parenchyma as a result of acute occlusion of supernumerary arteries - a new application for contrast-enhanced ultrasonography. - Grzelak P; Kurnatowska I; Sapiecha M; Durczynski A; Strzelczyk J; Nowicki M; Stefanczyk L (Annals of transplantation, 2011)