title: A novel mathematical model to predict the severity of postoperative functional reduction before partial nephrectomy: the importance of calculating resected and ischemic volume.
abstract: OBJECTIVE
  Preoperatively predicting postoperative kidney function is an essential step to achieve improved renal function and prevent chronic kidney disease. We introduce a novel formula especially to calculate resected and ischemic volume before partial nephrectomy. We examined whether resected and ischemic volume would have value for predicting postoperative renal function.
  
  
  METHODS
  We performed a retrospective cohort study in 210 patients who underwent robotic partial nephrectomy between September 2006 and October 2013 at a tertiary cancer care center. Based on abdominopelvic computerized tomography and magnetic resonance imaging we calculated resected and ischemic volume by the novel mathematical formula using integral calculus. We comparatively analyzed resected and ischemic volume, and current nephrometry systems to determine the degree of association and predictability regarding the severity of the postoperative functional reduction.
  
  
  RESULTS
  On multivariable analysis resected and ischemic volume showed a superior association with the absolute change in estimated glomerular filtration rate/percent change in estimated glomerular filtration rate (B = 6.5, p = 0.005/B = 6.35, p = 0.009). The ROC AUC revealed accurate predictability of resected and ischemic volume on the stratified event of an absolute change in estimated glomerular filtration rate/event of percent change in estimated glomerular filtration rate compared to 3 representative nephrometry systems. The calibration plot of this model was excellent (close to the 45-degree line) within the whole range of predicted probabilities.
  
  
  CONCLUSIONS
  We report a method of preoperatively calculating resected and ischemic volume with a novel formula. This method has superior correlation with the absolute and percent change in estimated glomerular filtration rate compared to current nephrometry systems. The predictive model achieved a strong correlation for the absolute and percent change in estimated glomerular filtration rate.
authors: Department of Urology, Chuncheon Sacred Hospital, College of Medicine, Hallym University, Chuncheon, Republic of Korea.
authors: Tae Young
authors: TY
authors: Shin
authors: Department of Urology, General Hospital of Nikaia St. Panteleimon, Athens, Greece.
authors: Christos
authors: C
authors: Komninos
authors: Biostatistics Collaboration Unit, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors: Dong Wook
authors: DW
authors: Kim
authors: Department of Mathematics, Hallym University, Chuncheon, Republic of Korea.
authors: Keum Sook
authors: KS
authors: So
authors: College of General Education, Hallym University, Chuncheon, Republic of Korea.
authors: Ki Seok
authors: KS
authors: Bang
authors: Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland.
authors: Heon-Jae
authors: HJ
authors: Jeong
authors: Department of Urology, Urological Science Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors: Woong Kyu
authors: WK
authors: Han
authors: Department of Urology, Urological Science Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors: Sung Jun
authors: SJ
authors: Hong
authors: Department of Urology, Urological Science Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors: Byung Ha
authors: BH
authors: Jung
authors: Department of Urology, Changi General Hospital, Singapore.
authors: Sey Kiat
authors: SK
authors: Lim
authors: Department of Urology, Chuncheon Sacred Hospital, College of Medicine, Hallym University, Chuncheon, Republic of Korea.
authors: Sang Kon
authors: SK
authors: Lee
authors: Department of Urology, Chuncheon Sacred Hospital, College of Medicine, Hallym University, Chuncheon, Republic of Korea.
authors: Won Ki
authors: WK
authors: Lee
authors: Department of Urology, Urological Science Institute, Yonsei University College of Medicine, Seoul, Republic of Korea. Electronic address: khrha@yuhs.ac.
authors: Koon Ho
authors: KH
authors: Rha
mesh_terms: D015331:Cohort Studies; D006801:Humans; D007668:Kidney / Q000098:blood supply* / Q000503:physiopathology* / Q000601:surgery; D008962:Models, Theoretical; D009392:Nephrectomy / Q000379:methods; D011183:Postoperative Complications / Q000503:physiopathology*; D011379:Prognosis; D012189:Retrospective Studies; D012720:Severity of Illness Index; D052096:Warm Ischemia
keywords: glomerular filtration rate; kidney neoplasms; mathematics; nephrectomy; prognosis