CHRONIC KIDNEY DISEASE PREDICTS GREATER 5-YEAR MORTALITY FOLLOWING MAJOR LIMB AMPUTATION

Objectives: Several studies have demonstrated that End-Stage Renal Disease (ESRD) predicts greater mortality after major lower extremity amputation (MLEA). However, it remains poorly understood whether this finding extends to patients with earlier stages of Chronic Kidney Disease (CKD). We aimed to assess outcomes for patients with any stage of CKD who underwent MLEA.

Methods: A retrospective chart review of all patients who underwent MLEA at a large tertiary referral center from 2015 to 2022. Inclusion criteria were age greater than 18 years and below-knee, through-knee, or above-knee amputations. Patients were stratified by renal dysfunction: None, Mild (CKD1 & 2), Moderate (CKD3a and 3b), or Severe (CKD4 or 5 or ESRD on dialysis). Outcomes were compared with Chi-Square bivariate analysis. Each statistically significant variable was then included in a multivariable Cox model. Kaplan-Meier analysis compared survival between groups using the log-rank test. All tests were two-tailed with a significance threshold of p < 0.05.

Results: 398 total patients had a mean postoperative survival time was 39 (± 26) months. 139 patients (34.9 %) had preoperative CKD diagnoses including 80 patients (20.1 %) with ESRD. More advanced stage of CKD was associated with preoperative diagnoses of Diabetes Mellitus, Hypertension, Hyperlipidemia, Peripheral Vascular Disease, Coronary Artery Disease, Heart Failure, and Opiate Abuse. More advanced stage of CKD was also associated with more frequent postoperative Acute Kidney Injury as well as less 1-year follow-up and greater 1- and 5-year mortality. Kaplan-Meier analysis showed less 5-year survival for patients with any stage of CKD (62%) compared to patients without CKD (81%; P < 0.001). Greater 5-year mortality was independently predicted by moderate CKD (hazard ratio (HR) 2.37, 95% CI: 1.14-4.94, P = 0.022) as well as severe CKD (HR 2.09, 95% CI: 1.24 - 3.51, P = 0.005).

Conclusion: These findings demonstrate that more advanced stage of CKD is associated with greater long-term mortality following MLEA. Further, even when controlling for the associations between CKD and many comorbidities, moderate and severe CKD remain significant predictors of greater long-term mortality. These findings highlight the importance of CKD diagnosis and treatment and incentivize further exploration of the underlying causal mechanisms. Novel interventions or management strategies that modify the effect of CKD on post-MLEA mortality could significantly improve both patient outcomes and health system expenditures.