Surgically Induced versus Medically Induced Chronic Kidney Disease: Renal Function Trajectories and Mortality in a Nationwide Danish Cohort Study (2009-2024)

Chronic kidney disease (CKD) after kidney surgery for renal cell carcinoma (RCC) is staged using the same eGFR and albuminuria thresholds as CKD of any other cause. The 2024 KDIGO guideline on CKD acknowledges etiology as a prognostic factor but does not address whether CKD from a surgical origin carries the same prognostic weight as CKD of medical origin. Single-centre US (Cleveland Clinic) cohort studies have investigated this, comparing surgically induced CKD (CKD-S) to CKD of purely medical origin (CKD-M) and to medical CKD present before surgery (CKD-M/S). They found that CKD-S follows a more stable course than CKD-M and CKD-M/S, with a prognosis resembling that of patients without CKD after surgery (Demirjian et al. 2014, DOI: 10.1016/j.juro.2014.04.016; Lane et al. 2015, DOI: 10.1016/j.eururo.2015.04.043). This is a proposed “missing link” in the nephron-sparring treatment versus radical nephrectomy debate, since the benefit of nephron-sparring treatment's better-preserved renal function depends on whether the CKD it prevents carries the same prognostic weight as other CKD (Parker et al. 2015, DOI: 10.1016/j.eururo.2015.06.001). This nationwide Danish registry cohort study applies the above stated etiology framework at a population level, extending the single-centre studies from Cleveland Clinic with a nationwide registry coverage. We will include all adults who underwent ablation therapy, partial or radical nephrectomy for primary incident stage I-III RCC in Denmark between 1 January 2009 and 31 December 2022, classified into three exposure groups (No CKD, CKD-S, CKD-M/S) 1 year after surgery, where follow-up will begin. A fourth exposure group, CKD-M, will be based on persons with two measurements of eGFR < 60 with 90 or more days apart registered in the National Danish Laboratory Register between 1 January 2009 and 31 December 2022. Follow-up will start on the date of the second measurement of eGFR < 60. Across all four exposure groups, persons undergoing kidney transplantation or dialysis before follow-up begins will be excluded. Renal progression and all-cause mortality are followed through 31 December 2024; non-RCC mortality through 31 December 2022. The primary aim is to determine whether CKD-S carries the same risk of progression and mortality as CKD-M and CKD-M/S. Prespecified subgroup analyses will stratify by surgical approach (PN vs RN) and pre-existing type 2 diabetes (T2D).