Increased urinary cystatin C level is associated with interstitial fibrosis and tubular atrophy in kidney allograft recipients

•Interstitial fibrosis/tubular atrophy is one of the main causes of allograft loss after renal transplantation.•Although kidney allograft biopsy is commonly used, it has limitations such as invasiveness and risk of potential morbidity.•The correlation between urinary cystatin C and IF/TA has not been studied in renal transplant recipients yet.•We investigated if urinary cystatin C could be a non-invasive laboratory marker of IF/TA in kidney transplant patients.•We report an association between high urinary cystatin C levels and IF/TA in kidney allograft recipients.

AimThe objective of this study was to investigate the correlation between the urinary excretion of cystatin C (CysC) and the presence of interstitial fibrosis/tubular atrophy (IF/TA) in renal transplant (RT) recipients.MethodsThis prospective study included 21 adult patients who had undergone renal biopsy and RT ≥ 6 months prior. According to the renal biopsy reports, the patients were divided into groups with (n = 12) or without (n = 9) IF/TA. Analytical parameters included the following: serum and urinary levels of CysC, creatinine (Cr) and sodium (Na), total urinary protein, urinary CysC/creatinine ratio [u(CysC/Cr)], fractional excretion of sodium (FENa) and estimated glomerular filtration rate (eGFR) based on the Chronic Kidney Disease Epidemiology Collaboration equation.ResultsThe values of uCysC, u(CysC/Cr), proteinuria, and FENa were significantly higher in patients with IF/TA than in patients without IF/TA. The values of eGFR were statistically lower in patients with IF/TA (p = 0.001). Values of uCysC significantly correlated with those of serum Cr, FENa, and eGFR (p < 0.001). Among the patients with IF/TA, 67% presented with glomerulosclerosis (segmental/global).ConclusionElevated levels of urinary CysC are associated with interstitial fibrosis and tubular atrophy in RT recipients and may become a useful tool for monitoring kidney allografts.