In kidney allograft protocol biopsies the presence of interstitial fibrosis and tubular atrophy (IF/TA) is associated with graft loss. In this study we sought to investigate the association of sterile leukocyturia (Leu+) with Banff criteria histological findings.

In this retrospective study we have evaluated all kidney transplants performed in our Institution between January 2006 and July 2010 who had an available urinalysis at the time of 6-month protocol biopsy. Patients who had a concomitant positive urine culture were excluded. Renal lesions were diagnosed according to the 2007 update of Banff 1997 classification.

We identified 189 patients with six-month protocol biopsy. Eleven were excluded because of insufficient histological sample, 47 because of unavailable urinalysis and 12 because of urinary tract infection. From the 119 evaluable cases, 24 displayed Leu+. Risk factors for Leu+ were female gender, deceased donor (DD) and delayed graft function (DGF). Renal function was similar between Leu+ and Leu- (sCrea 123±49 vs 127±49 mcmol/L). Regarding kidney graft histology findings, Leu+ was only associated with IFTA (75% vs 54%, P= 0.02). The overall IFTA prevalence in our study population was 54.6%. By univariate analysis risk factors for IFTA were Leu+, donor and recipient age, DGF, retransplantation and acute rejection. By multivariate analysis donor age (OR 1.036, P=0.009) and Leu+ (OR 2.74, P= 0.05) were the only predictors of IFTA. Sensitivity and specificity of Leu+ for predicting IFTA was 28% and 89% respectively. Nevertheless, the probability of IFTA with Leu+ and donor age ≥ 60 yr was 90% whereas it was 40% with Leu- and donor age <60 yr.

In the current omics era our results suggest that classical urinary sediment still provides valuable clinical information for the follow-up of kidney allograft recipients.

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