Aminoaciduria as a marker of acute renal transplant rejection--a patient study.

Over 12 months, urine samples were systematically collected from 40 children who underwent renal transplantation for the treatment of end-stage renal disease. Sequential determinations of the excretion of individual amino acids relative to that of creatinine were carried out on 15 subjects. Nine of these (including three who sustained episodes of acute rejection) retained a native kidney in-situ, while in six patients (including three who underwent an episode of acute rejection) both native kidneys had been removed. In both subgroups, the amino acid/creatinine ratios of early morning urine samples were higher shortly before clinical manifestations of acute rejection became evident than in patients who, following renal transplantation, had stable kidney function, chronic graft rejection, or acute tubular necrosis, with one exception: a patient with one native kidney in-situ in whom acute tubular necrosis developed immediately after transplantation. The amino acids showing the greatest increase included Thr, Ser, Gly, and Ala. These values fell dramatically immediately prior to the clinical episode of acute rejection, with Thr, Ala, and Phe showing the most consistent changes. These alterations in urinary amino acid excretion occurred several days before changes in urinary protein excretion or the serum concentrations of urea and creatinine, and may have a role to play in the monitoring of renal transplant recipients.