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.