Incidence, risk factors, and the impact of allograft pyelonephritis on renal allograft function.

BACKGROUND: The impact of allograft pyelonephritis (AGPN) on renal allograft function is controversial. In this study, we evaluated the incidence, risk factors, and the impact of AGPN on renal allograft function. METHODS: Retrospective cohort study in adult renal allograft recipients with 1-year follow-up after transplantation (Tx). Renal allograft function was evaluated by estimated glomerular filtration rate (eGFR) (by Modification of Diet in Renal Disease formula) and 24-h urine protein excretion. RESULTS: A total of 431 renal allograft recipients were analyzed; 57 (13.2%) developed AGPN within 1 year after Tx. Median time between Tx and AGPN was 50 days. Risk factors for AGPN were the presence of a urological catheter (odds ratio [OR] = 18.93, 95% confidence interval [CI] = 8.00-44.81, P < 0.001) and preceding asymptomatic bacteriuria (ASB) (OR = 2.16, 95% CI = 1.20-3.90, P = 0.009). In 72.7%, the causative microorganism of ASB was identical to that of the succeeding AGPN episode. Multivariable linear regression analysis showed that experiencing AGPN did not decrease the eGFR (P = 0.61) nor did increased proteinuria (P = 0.29) 1 year after Tx. For the eGFR, an interaction was found between AGPN/bacteriuria (BU) and acute rejection (AR): the group experiencing BU preceding AR had significantly (P < 0.001) lower eGFR compared with the group that experienced only AR (21 mL/min/1.73 m2 vs. 48 mL/min/1.73 m2 ), as a result of increased prevalence of combined rejections within the BU group. CONCLUSION: Indwelling urological catheters and preceding ASB are associated with developing AGPN. An incident of AGPN itself does not impair renal allograft function 1 year after Tx. However, a relevant interaction occurs between BU and AR, in which the sequence of occurrence of these 2 events synergistically impairs the eGFR.