The purpose of this study is to determine whether urinary connective tissue growth factor (uCTGF) can predict the onset of fibrosis in transplanted kidneys.

Since March 2004, and as part of routine clinical practice, protocol renal allograft biopsies are routinely performed at implantation and at 3, 12 and 24 months after transplantation, in all patients who receive a kidney transplant at the University Hospitals Leuven, unless there is a medical contra-indication or patient refusal to undergo this procedure. The biopsies are scheduled using a dedicated Microsoft Access database ("Biopsy Database"), that is maintained on the central servers of the University Hospitals Leuven. Patients who have an unexplained change in renal allograft function, undergo additional clinically indicated indication biopsies. These biopsies are also recorded in the aforementioned Microsoft Access Database.

All clinical data, including pretransplant donor and recipient characteristics, and post-transplant follow-up data are directly stored and maintained in a prospectively collected electronic database (CCL database until 06/2012, transferred to the central KWS database in 2012). This electronic database is the only existing clinical database for these patients, and contains all clinical patient charts. No written records are collected.

All renal allograft biopsies will be scored by a single renal pathologist according to the most recent Banff classification, blinded for the clinical parameters and timing of the biopsy. These rescoring data are directly entered in the dedicated Microsoft Access database ("Biopsy Database").

Inclusion Criteria:

• Patients who receive a primary or secondary single cadaveric or living donor renal allograft.
• Signed informed consent

Exclusion Criteria:

• Patients receiving a combined renal allograft.

Adult recipients of a primary or secondary cadaveric or living donor single renal allograft at the University Hospitals Leuven.