Association Between First Post-operative Day Urine Output Following Kidney Transplantation and Short-Term and Long-Term Outcomes: A Retrospective Cohort Study

Abstract

Background: The relationship between post-operative urine output (UO) following kidney transplantation and long-term graft function has not been well described. Objective: In this study, we examined the association between decreased UO on post-operative day 1 (POD1) and post-transplant outcomes. Design: This is a retrospective cohort study. Setting: Atlantic Canada. Patients: Patients from the 4 Atlantic Canadian provinces (Nova Scotia, New Brunswick, Newfoundland, and Prince Edward Island) who received a live or deceased donor kidney transplant from 2006 through 2019 through the multiorgan transplant program at the Queen Elizabeth II Health Sciences Centre (QEII) hospital in Halifax, Nova Scotia. Measurements: Using multivariable Cox proportional hazards models, we assessed the association of low POD1 UO (defined as ≤1000 mL) with death-censored graft loss (DCGL). In secondary analyses, we used adjusted logistic regression or Cox models as appropriate to assess the impact of UO on delayed graft function (DGF), prolonged length of stay (greater than the median for the entire cohort), and death. Results: Of the 991 patients included, 151 (15.2%) had a UO ≤1000 mL on POD1. Low UO was independently associated with DCGL (hazard ratio [HR] = 4.00, 95% confidence interval [CI] = 95% CI = 1.55-10.32), DGF (odds ratio [OR] = 45.25, 95% CI = 23.00-89.02), and prolonged length of stay (OR = 5.06, 95% CI = 2.95-8.69), but not death (HR = 0.81, 95% CI = 0.31-2.09). Limitations: This was a single-center, retrospective, observational study and therefore has inherent limitations of generalizability, data collection, and residual confounding. Conclusions: Overall, reduced post-operative UO following kidney transplantation is associated with an increased risk of DCGL, DGF, and prolonged hospital length of stay.