INTRODUCTION AND OBJECTIVE: For patients diagnosed with muscle invasive bladder cancer, baseline kidney function plays a significant role in selecting chemotherapy regimens and the type of urinary reconstruction at the time of cystectomy. We sought to characterize baseline kidney function among patients undergoing radical cystectomy, as well as long term kidney function following surgery. METHODS: We identified patients diagnosed with bladder cancer between 2004 and 2018 in the Veterans Health Administration. We linked cancer registry entries with diagnosis and procedure codes to characterize the type of reconstruction (ileal conduit vs. neobladder). We measured baseline kidney function using outpatient serum creatinine values within one year prior to surgery. We estimated post-operative kidney function using outpatient creatinine values starting 30 days after surgery to minimize the effect of surgical complications or acute kidney injury following cystectomy. RESULTS: We identified 3,361 bladder cancer patients that underwent radical cystectomy with 2,983 (89%) undergoing ileal conduit reconstruction and 378 (11%) undergoing neobladder reconstruction. Comorbidity was similar by reconstruction type (Charlson Comorbidity Index 2.4 +/- 2.0 in neobladder vs. 2.8 +/- 2.3 in ileal conduit cohorts). Mean baseline eGFR was 70.2 for neobladder patients vs. 66.7 in the ileal conduit group. Kidney function declined at 3 months post surgery to 55.1 and 54.2 for neobladder and ileal conduit groups, respectively. The median time to reach clinically significant renal disease (eGFR <30) was shorter in the ileal conduit group at 14.8 months vs. 20.1 months in the neobladder cohort. For patients with normal baseline kidney function (eGFR>60) 73% of neobladder and 67% of ileal conduit patients experienced at least one eGFR <60, raising concern about eligibility for cisplatin-based adjuvant chemotherapy after radical cystectomy. CONCLUSIONS: Kidney function declines after radical cystectomy with either neobladder or ileal conduit urinary diversion. Many patients experience renal morbidity that may increase their risk of cardiovascular events and affect adjuvant treatment selection.Source of Funding: none