Correlation of Volume Loss with Functional Change in Robot Assisted Nephron Sparing Surgery: A Short Term Prospective Study

Introduction and Objective: Function loss following Robot assisted nephron sparing surgery (RANSS) also termed as Robot partial nephrectomy occurs due to ischemia during vessel clamping, normal parenchyma loss with the specimen and loss due to ischemia during suturing. We tried to put an insight into the function loss due to warm ischemia and excised parenchyma using simple mathematical formulae. Material and Method Eighty-five patients underwent RANSS during January 2016 to March 2017. Pre-operative and 3 months post-operative glomerular filtration rate (GFR) by DTPA scan and CT volume by cylinder formula were compared. Normal renal parenchyma volume excised with specimen was calculated using ellipsoid formula. Results pT1b tumor was 56.4 % and pT2a was 4.7 %. Warm ischemia time (WIT) was high (greater than 30 minutes) in 16 patients. RENAL nephrometry score was greater than 10 in 11 patients. Mean split GFR of the affected kidney was 40.8 12.9 ml/min/1.73 m2, which fell to 32.2 12.4 ml/min/1.73 m2. Mean loss of normal parenchyma excised was 20.70 22.4 cc, while mean loss of kidney volume on CT was 22.69 11.3 cc. CKD upstaging was seen in 16 patients. Age (p = 0.002), baseline serum creatinine (p = 0.003), tumor size (p = 0.039) and volume of normal kidney tissue excised with specimen (p =