Graft Function, Albuminuria, and the Risk of Hemorrhage and Thrombosis After Kidney Transplantation

Abstract

Background: Compared to the general population, kidney transplant recipients are at increased risk of hemorrhage and thrombosis. Whether this risk is affected by graft function and albuminuria is unknown. Objective: To determine the association between graft function and albuminuria and the risk of post-transplant hemorrhage and thrombosis. Design: Retrospective cohort study. Setting: We used linked health care databases in Alberta, Canada. Patients/sample/participants: We included adult kidney transplant recipients from 2002 to 2015 with a functioning graft at 1 year. Measurements: Estimated glomerular filtration rate (eGFR) and albuminuria measurements at 1 year post-transplant were used to categorize recipients (eGFR: ≥45 vs. <45 mL/min/1.73 m2; albuminuria: absence vs. presence). We determined the rates of post-transplant hemorrhage and venous thrombosis based on validated diagnostic and procedural codes. Methods: We determined the association between categories of eGFR and albuminuria and post-transplant hemorrhage and venous thrombosis using Poisson regression with log link. Results: Of 1284 kidney transplant recipients, 21% had an eGFR <45 mL/min/1.73 m2 and 40% had presence of albuminuria at 1 year post-transplant. Over a median follow-up of 6 years, there were 100 hemorrhages (12.6 events per 1000 person-years) and 57 venous thrombosis events (7.1 events per 1000 person-years). The age- and sex-adjusted rate of hemorrhage and thrombosis was over 2-fold higher in recipients with lower eGFR and presence of albuminuria compared to higher eGFR and no albuminuria (hemorrhage: incidence rate ratio, IRR, 2.6, 95% confidence interval [CI]: 1.5-4.4, P = .001; thrombosis: IRR, 2.3, 95% CI: 1.1-5.0, P = .046). Limitations: Complete relevant medication information, such as anticoagulants, were not available in our datasets. Due to sample size, this study was underpowered to conduct a fully adjusted analysis. Conclusion: Among kidney transplant recipients, lower eGFR and presence of albuminuria at 1 year post-transplant were associated with an over 2-fold higher risk of hemorrhage and venous thrombosis. Graft function and albuminuria at 1 year post-transplant are important prognostic factors in determining risk of post-transplant hemorrhage and venous thrombosis. Further research, including medication data, are needed to further delineate outcomes and safety. Trial registration: Not applicable (cohort study).