Prevalance and the causes of proteinuria in kidney transplant recipients

Objectives: In this study our purpose was to determine the proteinuria prevalence and its causes in kidney transplant recipients.Materials and Methods: All kidney transplant recipients, followed by Nephrology Division of the Department of Internal Medicine in Dokuz Eylül University Faculty of Medicine were included in this study. The etiology of chronic kidney disease and the donor characteristics (age, sex, and cadaver/live-donor) were obtained from outpatient follow-up records. Proteinuria levels, assessed by 24-hour urine collection, and creatinine clearances recorded at 3, 6, 9, 12-Months and, annually thereafter, following the transplantation. Newly onset hypertension, diabetes mellitus and the infections (cytomegalovirus (CMV) and polyoma (BK) virus nephritis) were recorded. Immunosuppressive treatments and the renal biopsies, applied during the follow up period, were also noted.Results: A total of 260 kidney transplant recipients (97 female, mean age 42,3±12,3) were included and evaluated. Mean age of donors was 42,7±15 years. Of the donors, 133 were female. 137 of all kidney transplantations were from live-donor. Median follow-up period was 36 months (3-360). Overt proteinuria was defined as more than 300 mg daily excretion. According to the definition, overt proteinuria was detected in 92 patients (35,4%). Median time to overt proteinuria was 24 months. There was no significant difference between the groups with or without overt proteinuria in respect to age, sex, donor characteristics and the etiology of the chronic kidney disease. In patients with overt proteinuria, 15 biopsies were obtained contemporary with the proteinuria. No significant difference was found in respect to pathological diagnosis. Of patients with a proteinuria below 300 mg/day, 48 had undergone biopsy. None of the patients with a proteinuria below 300 mg/day appeared to have glomerulonephritis. Mean creatinine clearance was significantly higher in the patients with less than 300 mg/day proteinuria compared with the patients who had overt proteinuria (68,70 ± 18,53 mg/dl, 63 ± 24,10 mg/dl, p=0,04) The level of proteinuria was found to be higher among patients receiving mTOR inhibitors compared to those receiving calcineurin inhibitors; however, this was not statistically significant (p=0.4).Conclusion: The prevalence of proteinuria was found to be 35,4%. The immunologic events, like all kinds of rejections, were the most common cause of overt proteinuria. However using mTOR inhibitors were not related with increased frequency of overt proteinuria. This can be related with the small size of the evaluated patient population.Key Words: Kidney Transplant, Proteinuria