Rescue Kidneys in Lung Transplantation: A Retrospective Analysis of Recipients Who Might Have Benefitted from a Kidney Safety Net.

Abstract

Introduction: In 2023, a new UNOS policy established criteria for a kidney allocation safety net for lung transplant recipients (LTRs) with chronic renal dysfunction. We sought to evaluate the demographics and outcomes of past lung transplant recipients who would have been eligible for a rescue kidney under the new criteria.

Methods: Using the UNOS OPTN registry, we identified lung transplant recipients from 2005-2023 who fit the eligibility for rescue kidneys. Rescue kidney eligibility was defined as recipients who had an eGFR≤20mL/min, CrCl≤20mL/min, or were receiving chronic dialysis at any point 60 to 365 days post-transplant. Baseline characteristics and survival out to 1 and 3 years were evaluated for the rescue kidney-eligible cohort compared to all other lung transplant recipients in the study period.

Results: 554 (2.1%) of all recipients would have been eligible for a rescue kidney under the new policy. Comparing to non-eligible group, they were older (median, 62 vs 61 years; P <.001), had higher BMI (27 vs 26; P <.001), and were more often Black (13% vs 9%; P <.001). They also had a significantly higher proportion of renal dysfunction (including CKD stage III, IV and V) at the time of transplant (17% vs 7%; P <.001) and higher likelihood of pre-transplant dialysis (7% vs 0%; P <.001). The rescue-eligible recipients had higher rates of life support (14% vs 11%; P =.031) and greater LAS at transplant (median 40 vs 39; P <.01). Compared to non-eligible recipients, rescue kidney-eligible recipients had lower survival at 1 year (42% vs. 88%, p<.001) and 3 years (28% vs. 71%, p<.001). These differences in mortality risk persisted after adjusting for donor and recipient characteristics (1-year mortality aHR 9.27; 95% CI 8.16-10.55; P <.001; 3-year aHR 5.55; 95% CI 4.97-6.20; P <.001).

Conclusion: While relatively few recipients would have been eligible for a rescue kidney under the new policy, they had significantly worse survival than non-eligible recipients. This underscores the severe illness of these patients and the importance of assessing whether rescue kidneys can reduce these mortality differences.