Investigating a Novel Modifiable Factor Affecting Renal Function After Partial Nephrectomy: Cortical Renorrhaphy

Overview

Preserving kidney function during removal of a kidney tumor is becoming increasingly important as rates of chronic kidney disease increase. A novel modifiable factor (suture closure of the defect caused by tumor removal) was discovered on retrospective studies to account for nearly two-thirds of the 15% volume loss commonly seen in operated kidneys. We hypothesize that a randomized controlled surgical trial will show that omitting the suture closure both preserves renal function and will not lead to unreasonable postoperative complications.

Purpose: To evaluate a never before studied modifiable factor affecting renal function after partial nephrectomy: the suture closure of the renal cortex after tumor removal (renorrhaphy). Background: There is increasing interest in preserving renal function when removing renal tumors. This is partly due to studies that link chronic kidney disease with cardiovascular events and overall survival. There is an approximate loss of 10% overall renal function after partial nephrectomy along with a loss of 15% of the volume in the operated kidney. Studies point to 3 factors leading to this loss in renal function after partial nephrectomy: 1) Poor preoperative renal function, 2) Ischemia time (clamping the renal blood vessels to decrease bleeding during surgery, and 3) Loss in renal volume from the surgery. The only factor that is considered modifiable is ischemia time, especially when over 20-25-minutes in duration. Modern techniques now aid in keeping the ischemia time below the 25-minute cutoff. Leading experts from institutions such as the Cleveland Clinic, The University of Southern California, and The Mayo Clinic have concluded that the most important factor in preserving renal function, renal volume loss, is not modifiable. Specific Aims: Our question is: if we are removing non-functional tissue (tumor) then why is there a loss in renal volume (15%) and function (10%)? We hypothesize that by omitting one particular step during surgery, sewing closed the defect caused by tumor removal, we will be able to improve renal volume loss and function (RENORRHAPHY CLIP http://youtu.be/NXOtUHdigj4). Indiana University is in a unique position to study this hypothesis as two of our surgeons have routinely omitted closing the defect left after tumor removal (NO RENORRHAPHY CLIP http://youtu.be/ZisMjrm85s8). In a recently accepted abstract, we discovered that omitting the cortical closure (n=28) resulted in a 0.8% loss in glomerular filtration rate while using the closure resulted in a 7.3% loss (p=0.03). Following this discovery a 3D modeling project was performed to isolate the volume loss in operated kidneys using pre- and postoperative CT scans (not yet published). In this study, we discovered a 15% volume loss with cortical closure (n=38) compared to only a 5% loss without closure (n=20, p \< 0.001). Bias and confounders cannot completely be removed from our retrospective data making it hard to believe that others will consider our hypothesis without a randomized controlled trial (RCT). We propose a RCT for robotic partial nephrectomy (20 stitch closure vs. 20 no stitch closure) with the primary outcome being volume change in the affected kidney.

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