Survival and Functional Stability in Chronic Kidney Disease Due to Surgical Removal of Nephrons: Importance of the New Baseline Glomerular Filtration Rate.

BACKGROUND: Chronic kidney disease (CKD) can be associated with a higher risk of progression to end-stage renal disease and mortality, but the etiology of nephron loss may modify this. Previous studies suggested that CKD primarily due to surgical removal of nephrons (CKD-S) may be more stable and associated with better survival than CKD due to medical causes (CKD-M).

OBJECTIVE: We addressed limitations of our previous work with comprehensive control for confounding factors, differentiation of non-renal cancer-related mortality, and longer follow-up for more discriminatory assessment of the impact of CKD-S.

DESIGN, SETTING, AND PARTICIPANTS: From 1999 to 2008, 4299 patients underwent surgery for renal cancer at a single institution. The median follow-up was 9.4 yr (7.3-11.0). The new baseline glomerular filtration rate (GFR) was defined as the highest GFR between the nadir and 42 d after surgery. Three cohorts were retrospectively evaluated: no CKD (new baseline GFR >60 ml/min/1.73 m(2)); CKD-S (new baseline GFR<60 but preoperative >60 ml/min/1.73 m(2)); and CKD-M/S (new baseline and preoperative GFR both <60 ml/min/1.73 m(2)). Cohort status was permanently set at 42 d after surgery.

INTERVENTION: Renal surgery.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Decline in renal function (50% reduction in GFR or dialysis), all-cause mortality, and non-renal cancer mortality were examined using a multivariable Cox proportional hazards model.

RESULTS AND LIMITATIONS: CKD-M/S had a higher incidence of relevant comorbidities and the new baseline GFR was lower. On multivariable analysis (controlling for age, gender, race, diabetes, hypertension, and cardiac disease), CKD-M/S had higher rates of progressive decline in renal function, all-cause mortality, and non-renal cancer mortality when compared to CKD-S and no CKD (hazard ratio [HR] 1.69-2.33, all p<0.05). All-cause mortality was modestly higher for CKD-S than for no CKD (HR 1.19, p=0.030), but renal stability and non-renal cancer mortality were similar for these groups. New baseline GFR of <45 ml/min/1.73 m(2) significantly predicted adverse outcomes. The main limitation is the retrospective design.

CONCLUSIONS: CKD-S is more stable than CKD-M/S and has better survival, approximating that for no CKD. However, if the new baseline GFR is <45 ml/min/1.73 m(2), the risks of functional decline and mortality increase. These findings may influence counseling for patients with localized renal cell carcinoma and higher oncologic potential when a normal contralateral kidney is present.

PATIENT SUMMARY: Survival is better for surgically induced chronic kidney disease (CKD) than for medically induced CKD, particularly if the postoperative glomerular filtration rate is ≥45 ml/min/1.73 m(2). Patients with preexisting CKD are at risk of a significant decline in kidney function after surgery, and kidney-preserving treatment should be strongly considered in such cases.