Transplant kidney biopsy for proteinuria with stable creatinine: Findings and outcomes.

Introduction Little is known aboutbiopsy findings and outcomes when kidney transplant recipients (KTRs) undergo biopsy for isolated proteinuria with stable serum creatinine (SCr). Methods We analyzed all KTRs who underwent biopsy for isolated proteinuria with stable SCr between January 2016 and June 2020. Patients were divided into three groups based on the biopsy findings: Active Rejection (AR), Glomerulonephritis (GN), and Other. Results A total of 130 KTRs fulfilled our selection criteria; 38 (29%) in the AR group, 26 (20%) in the GN group, and 66 (51%) in the Other group. Most baseline characteristics were similar between the groups. In multivariate analysis, higher HLA mismatch (HR per mismatch: 1.30; 95% CI:1.06-1.59; P = .01) and male gender (HR: .45; 95% CI .23-.89; P = .02) were associated with AR. There was no significant correlation between the degree of proteinuria and rejection (r = .05, P = .58) or GN (r = .07, P = .53). Graft survival was also similar between the groups. Likely due to the early diagnosis without a significant rise in SCr, outcomes were similar among all three groups. Conclusion Routine monitoring for proteinuria followed by a biopsy and appropriate management may help to identify early acute graft injury and prevent graft failure.