Chronic kidney disease after nephrectomy in patients with renal cortical tumours: a retrospective cohort study

Summary

Background

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.

Methods

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.

Findings

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).

Interpretation

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.

Introduction

Radical nephrectomy has been the gold standard treatment for localised renal cortical tumours for nearly 40 years.¹ However, surgical management of these tumours has evolved greatly in the past decade. Advances in abdominal imaging have led to increased detection of small (≤4 cm), localised, incidental, renal cortical tumours, which account for 60–70% of all diagnosed renal masses.² Because of the small size and early stage of these tumours, surgeons are able to do partial nephrectomies without compromising safety and oncological efficacy.3, 4

In tertiary-care centres in the USA, partial nephrectomy now accounts for 30–65% of all surgical procedures for renal cortical tumours.5, 6, 7 However, this trend does not represent current US surgical practice for renal cortical tumours. Analysis of the Nationwide Inpatient Sample⁸ showed that nationally, only 7·5% of all kidney-cancer cases between 1988 and 2002 were treated with partial nephrectomy. Similarly, data from the population-based Surveillance Epidemiology and End Results (SEER) registry⁹ showed that from 2001, only 20% of all renal cortical tumours with a size of 2–4 cm were preferentially treated with partial nephrectomy. This practice pattern is seen in other countries with advanced health-care systems. Data from the Hospital Episode Statistics database of the Department of Health in England¹⁰ shows that of the 2671 nephrectomies done in England in 2002, only 108 (4%) were partial nephrectomies.

Such findings are worrying, because the surgical management of small renal cortical tumours could greatly impair the kidney function of patients, including those with two healthy kidneys. Previous studies11, 12 have shown a significantly increased risk of renal insufficiency, defined as concentrations of serum creatinine greater than 177 μmol/L (2 mg/dL), in patients undergoing radical nephrectomy compared with those undergoing partial nephrectomy. However, these studies are restricted by the fact that serum creatinine is an inaccurate measure of overall kidney function, and that a clinically relevant reduction in kidney function occurs in patients with serum creatinine concentrations lower than 177 μmol/L.13, 14

Current guidelines define chronic kidney disease as an estimated glomerular fitration rate (GFR) lower than 60 mL/min per 1·73 m², or by the presence of markers of kidney damage (such as albuminuria or abnormal imaging studies) for 3 months or more.¹⁵ The major outcomes of chronic kidney disease are: loss of kidney function, sometimes leading to kidney failure; complications of reduced kidney function, such as hypertension, anaemia, malnutrition, neuropathy, and reduced quality of life; and increased risk of cardiovascular disease and mortality.16, 17, 18 Because of raised awareness of important health risks associated with chronic kidney disease,15, 16, 17, 18, 19 and worldwide data8, 9, 10 showing the probable overuse of radical nephrectomy, we aimed to review our nephrectomy database and assess kidney function outcomes in patients undergoing surgery for small, solitary, renal cortical tumours.