Chronic kidney disease is a graded and independent risk factor for substantial comorbidity and death. We aimed to examine new onset of chronic kidney disease in patients with small, renal cortical tumours undergoing radical or partial nephrectomy.

We did a retrospective cohort study of 662 patients with a normal concentration of serum creatinine and two healthy kidneys undergoing elective partial or radical nephrectomy for a solitary, renal cortical tumour (≤4 cm) between 1989 and 2005 at a referral cancer centre. Glomerular filtration rate (GFR) was estimated with the abbreviated Modification in Diet and Renal Disease Study equation. Separate analysis was undertaken, with chronic kidney disease defined as GFR lower than 60 mL/min per 1·73 m² and GFR lower than 45 mL/min per 1·73 m².

171 (26%) patients had pre-existing chronic kidney disease before surgery. After surgery, the 3-year probability of freedom from new onset of GFR lower than 60 mL/min per 1·73 m² was 80% (95% CI 73–85) after partial nephrectomy and 35% (28–43; p<0·0001) after radical nephrectomy; corresponding values for GFRs lower than 45 mL/min per 1·73 m² were 95% (91–98) and 64% (56–70; p<0·0001), respectively. Multivariable analysis showed that radical nephrectomy remained an independent risk factor for patients developing new onset of GFR lower than 60 mL/min per 1·73 m² (hazard ratio 3·82 [95% CI 2·75–5·32]) and 45 mL/min per 1·73 m² (11·8 [6·24–22·4]; both p<0·0001).

Because the baseline kidney function of patients with renal cortical tumours is lower than previously thought, accurate assessment of kidney function is essential before surgery. Radical nephrectomy is a significant risk factor for the development of chronic kidney disease and might no longer be regarded as the gold standard treatment for small, renal cortical tumours.