Clinical significance of proteinuria at posttransplant year 1 in kidney transplantation

Purpose: Proteinuria in the nontransplant population is a progressive renal disease. We analyzed the prevalence and clinical significance of proteinuria as well as factors related to its degree at posttransplant year 1 among kidney transplant recipients. Methods: We measured protein in a 24-hour urine among 644 recipients from January 1996 to December 2010. Results: Among 372 male and 272 female recipients, the mean amount of urinary protein was 424.4 ± 1010 mg/d (range, 13.88-8691) including 388 (60.2%) subjects with microproteinuria and the other 256 (39.8%) with overt proteinuria. Nephrotic range proteinuria was observed in 17 (2.6%) and nonnephritic range proteinuria, in 239 (37.1%) recipients. The latter cohort was categorized into low-grade proteinuria (n = 224; 34.8%) and high-grade proteinuria (n = 15; 2.3%). Proteinuria at posttransplant 1 year highly correlated with serum creatinine values at posttransplant years 1 and 2 as well as estimated glomerular filtration rate but not creatinine clearance at postoperative year 2. A greater incidence of graft loss was observed among recipients with more severe proteinuria. Males, recipients with anti-hepatitis C virus antibody, unrelated donors, anti-thymocyte immunoglobulin at the time of reperfusion, maintenance immunosuppression with cyclosporine or without mycophenolate mofetil were strongly associated with the amount of proteinuria. Conclusion: This study demonstrated the prevalence of proteinuria in kidney transplant recipient to be high. The presence as well as level of proteinuria were predictive markers for inferior allograft function.