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C-index is associated with functional outcomes after laparoscopic partial nephrectomy
Mary K Samplaski1, Adrian Hernandez, Inderbir S Gill
1Department of Urological Oncology, Glickman Urologic and Kidney Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Purpose:
The C-index is a morphometric descriptor of renal masses that incorporates tumor size and site. We examined associations of the C-index with kidney function after laparoscopic partial nephrectomy.
Materials And Methods:
We retrospectively reviewed the records of 131 patients who underwent laparoscopic partial nephrectomy for a single kidney tumor. We calculated the C-index from preoperative contrast enhanced computerized tomography images. Estimated glomerular filtration rate was calculated using the modification of diet in renal disease 2 equation. Nadir estimated glomerular filtration rate was calculated using peak serum creatinine within 7 days of surgery.
Results:
The median C-index was 2.7 (range 0.7 to 9.6). The median preoperative and nadir estimated glomerular filtration rate was 78 (range 23 to 148) and 54 ml/minute/1.73 m2 (range 15 to 127, p<0.001). The mean±SD total glomerular filtration rate decrease was 28%±16%. On univariate analysis we noted a positive correlation between log C-index and the nadir estimated glomerular filtration rate (r=0.29, p=0.002), and a negative correlation between log C-index and the percent decrease in the estimated glomerular filtration rate (r=-0.4, p<0.001). On multivariate analysis the estimated glomerular filtration rate percent decrease was significantly associated with log C-index (p=0.005) and warm ischemia time (p<0.001) but not with tumor diameter or the preoperative estimated glomerular filtration rate. Of patients with a C-index of 2.5 or less 70% showed a 30% or greater decrease in the estimated glomerular filtration rate vs 32% of those with a C-index of greater than 2.5 (RR 2.2, p<0.001).
Conclusions:
The C-index is associated with the postoperative nadir estimated glomerular filtration rate and the percent decrease in the estimated glomerular filtration rate after laparoscopic partial nephrectomy. A C-index of less than 2.5 correlated with a 2.2-fold increased risk of a 30% or greater estimated glomerular filtration rate decrease after laparoscopic partial nephrectomy.