Histologic acute graft pyelonephritis after kidney transplantation: Incidence, clinical characteristics, risk factors, and association with graft loss

Background Histologic acute graft pyelonephritis (HAGPN) after kidney transplantation (KT) has been assessed less frequently than urinary tract infections (UTIs) or clinical acute graft pyelonephritis. Risk factors for HAGPN, its association with graft loss, and measures that might prevent it are not known. Methods We performed a retrospective review of HAGPN cases identified from KT occurring between January 2008 and December 2017 at our institution. We compared the HAGPN cases to a randomly selected control group of KTs to identify risk factors using univariate and multivariate Cox regression models. The association between HAGPN and graft loss was also assessed, similarly. Results HAGPN was identified in 46 of 1391 patients (cumulative incidence, 5% [95% CI, 3%-7%]) undergoing KT at a single center from January 2008 through December 2017 (median time to diagnosis, 241 days after KT; interquartile range, 122-755 days). Indications for biopsy were follow-up of treated rejection (n = 20 [43%]), KT protocol biopsy (n = 19 [41%]), and acute kidney injury (n = 7 [15%]). Histologic rejection, UTI, and asymptomatic bacteriuria (ASB) were present in 23 (50%), 9 (20%), and 16 (35%). Multivariate Cox proportional hazards models comparing KT recipients with or without HAGPN (n = 46 and n = 138, respectively) showed that HAGPN was associated with urologic complication by day 30, delayed graft function, previous UTI or ASB, and a history of rejection. In the univariate and multivariate analyses, HAGPN was associated with an increased risk of graft loss. Conclusion HAGPN is an infrequent, unanticipated, and clinically significant complication of KT.