Transcellular creatinine disequilibrium and its significance in hemodialysis. Creatinine and urea transcellular disequilibria were searched for on the venous side of a hemodialysis machine and in patients immediately following dialysis. Results indicated: (1) hemodialysis induces disequilibrium of creatinine but not for urea, between red cells and plasma on the venous side of a dialyzer; (2) much of the rapid rise in plasma creatinine concentration during the first hour following dialysis probably results from dissipation of a generalized transcellular creatinine disequilibrium, and (3) transerythrocytic creatinine disequilibrium necessitates incubation of dialyzer venous blood samples prior to plasma creatinine determination.