Association of pre-existing chronic kidney disease with in-hospital mortality and resource utilization among U.S. solid tumor hospitalizations: A National Inpatient Sample analysis, 2018–2022.

e23166 Background: Chronic kidney disease (CKD) is prevalent among patients with cancer and may adversely influence inpatient outcomes through baseline physiologic vulnerability and constraints on diagnostic and therapeutic management. Nationally representative estimates describing the inpatient impact of CKD among hospitalizations primarily for solid tumors remain limited. Methods: A retrospective, hospitalization-level cohort study was conducted using the Healthcare Cost and Utilization Project National Inpatient Sample (NIS), 2018–2022. Adult hospitalizations with a principal diagnosis of solid tumor malignancy were identified using ICD-10-CM diagnosis codes, excluding hematologic malignancies. Pre-existing CKD was defined by ICD-10-CM code N18* in any diagnosis position, including end-stage renal disease (ESRD; N18.6). Acute kidney injury (AKI; N17*) was assessed in sensitivity analyses. Survey-weighted analyses incorporated NIS discharge weights, hospital clustering, and stratification to generate nationally representative estimates. Outcomes included in-hospital mortality, length of stay (LOS), and total hospitalization charges as a proxy for inpatient resource utilization. Multivariable survey-weighted logistic regression adjusted for age, sex, race, median household income quartile, and primary payer. Results: An estimated 4,298,089 hospitalizations with a principal diagnosis of solid tumor malignancy were identified (95% CI 4,197,740–4,398,438). CKD was present in 11.84% of hospitalizations (95% CI 11.71%–11.97%), including ESRD in 0.98% (95% CI 0.95%–1.00%). In-hospital mortality was higher among hospitalizations with CKD compared with those without CKD (5.41% [95% CI 5.24%–5.58%] vs 3.88% [95% CI 3.76%–4.01%]; absolute difference 1.52%). Hospitalizations with CKD had longer mean LOS (7.14 vs 6.00 days) and higher mean charges ($103,602 vs $98,613). In sensitivity analyses excluding AKI, mortality remained higher among hospitalizations with CKD (3.07% vs 2.75%). After multivariable adjustment, CKD remained independently associated with increased in-hospital mortality (adjusted odds ratio 1.25, 95% CI 1.20–1.30; p < 0.001). Conclusions: In a nationally representative sample of U.S. hospitalizations primarily for solid tumors, pre-existing CKD was common and independently associated with higher in-hospital mortality and increased inpatient resource utilization, with persistence of mortality differences after exclusion of AKI. These findings underscore CKD as an important baseline risk marker in hospitalized oncology populations and highlight the need for kidney-adaptive, system-level inpatient care strategies.