The Transplantation Science Symposium Asian Regional MeetingKidney transplantationClinicopathologic Impact of Early Medullary Ray Injury in Patients Following Kidney Transplantation

BackgroundPreviously, we explored the histopathologic characteristics of medullary ray injury (MRI) inducing interstitial fibrosis and tubular atrophy (IF/TA) to determine its etiologies, which include calcineurin inhibitor (CNI) toxicity and urologic complications. However, we did not examine the effects of these etiologies on long-term kidney allograft prognosis, because biopsy timing differed among cases.AimWe examined the influence of early MRI on kidney allograft prognosis using protocol biopsies taken within a 3-month time frame.MethodsWe defined early MRI as tubular degeneration with interstitial edema or mild fibrosis localized to the medullary ray. We divided 53 protocol biopsies into 2 groups, with and without early MRI. Early MRI+ cases with isometric vacuolization were classified as CNI toxicity; those with Tamm-Horsfall protein in the interstitium and a thyroidlike appearance were classified as urinary tract system abnormalities; remaining cases were classified as “others.” We compared changes in serum levels of creatinine (sCr) over 3 years and fibrosis extent at 1 year.ResultsThe sCr levels were significantly higher in the MRI+ group than the MRI− group at 3 years (P = .024). Examining the 3 MRI+ subgroups, only the MRI+ urinary tract system abnormalities group had significantly high sCr levels compared to the MRI− group (P = .019). The MRI+ group showed significant signs of IF/TA at 1 year.ConclusionsEarly MRI after kidney transplantation was significantly more likely to develop IF/TA at 1 year and had higher sCr levels at 3 years. In such cases, intervention might preserve graft function over the long term.