Urinary protein analysis in the early detection of acute rejection episodes after renal transplantation in children.

The purpose of the present longitudinal investigation was to assess the predictive value of urinary protein analysis in the early detection of rejection crisis after renal transplantation. Forty-one children were studied consecutively over a period of 6 months applying the following methods: creatinine clearance (Ccr); urinary total protein (UTP); and electrophoretic differentiation of urinary proteins according to their molecular size by microgradient-gel electrophoresis (MGGE) with a continuous concentration gradient of 4-40% of polyacrylamide. Protein fractions analyzed were albumin (69,000 d), low molecular weight proteins (LMW-proteins, less than 69,000 d), and high molecular weight proteins (HMW-proteins, greater than 69,000 d). No rejection was observed in 30 children (group A), a total of 18 rejection episodes occurred in 11 children (group B). UTP was significantly lower in group A as compared to group B (107 vs 376 mg/m2/24 h), but no differences in urinary protein pattern were observed between group A and group B prior to rejection. One to two days after rejection UTP increased to 938 mg/m2/24 h, and 3-7 days after rejection LMW-protein fraction increased from 9% to 23% with a corresponding decrease of albumin fraction from 71% to 56% of UTP. No qualitative changes were noted in respect to HMW-protein excretion. It is concluded that changes of UTP and urinary protein pattern occur during rejection episodes but are of no predictive value in detecting rejection before clinical symptoms appear.