title: Role of calculated glomerular filtration rate using percutaneous nephrostomy creatinine clearance in the era of radionuclide scintigraphy.
abstract: BACKGROUND
  Gates method tends to over-estimate glomerular filtration rate (GFR) in borderline functioning kidneys. We study the role of calculated GFR in these cases in decision-making regarding performing kidney-sparing surgery or nephrectomy.
  
  
  OBJECTIVE
  The aim of this study is to find the correlation between GFR calculated by percutaneous nephrostomy (PCN) urine creatinine clearance in obstructed kidneys and GFR by radionuclide scintigraphy. It also studies the role of this calculated GFR in borderline functioning kidneys.
  
  
  METHODS
  Single tertiary care center; retrospective.
  
  
  METHODS
  A total of 46 patients in whom PCN was inserted as an emergency measure in an obstructed kidney and for whom diethylene-triamine-penta-acetic acid/ethylene-di-cysteine (DTPA/EC) scan was also done (Gates method) were analyzed retrospectively. PCN creatinine clearance was calculated for 3 consecutive days, and the mean value was used.
  
  
  METHODS
  Pearson's correlational analysis; Chi-square test.
  
  
  RESULTS
  Overall strong correlation was found between the two GFR values (Pearson'sr= 0.540692,P< 0.001). Totally 26 patients (56.52%) had comparable GFR values (P> 0.05). Among the 36 patients with borderline functioning kidneys, DTPA/EC scan significantly over-estimated GFR in one-third of the patients. The management plan was changed in 7 out of those patients (46.67%), with nephrectomy performed in all instead of kidney-sparing procedure. When the highest value of calculated GFR was compared, 28 patients had comparable GFRs (60.87%).
  
  
  CONCLUSIONS
  GFR based on radionuclide scintigraphy may be insufficient for evaluation of residual renal function to determine the management of obstructed kidney with borderline function. For adequate decision-making, other factors including creatinine clearance via PCN should also be considered. Gates method tends to overestimate GFR as compared to calculated creatinine clearance at low GFR levels.
authors.affiliation: Department of Urology, Lokmanya Tilak Municipal Medical College and General Hospital, Mumbai, Maharastra, India.
authors.forename: Sunil Raghunath
authors.initials: SR
authors.lastname: Patil
authors.affiliation: Department of Urology, Lokmanya Tilak Municipal Medical College and General Hospital, Mumbai, Maharastra, India.
authors.forename: Prakash Wamanrao
authors.initials: PW
authors.lastname: Pawar
authors.affiliation: Department of Urology, Lokmanya Tilak Municipal Medical College and General Hospital, Mumbai, Maharastra, India.
authors.forename: Abhishek Jaysukhbhai
authors.initials: AJ
authors.lastname: Savalia
authors.affiliation: Department of Urology, Lokmanya Tilak Municipal Medical College and General Hospital, Mumbai, Maharastra, India.
authors.forename: Shankar Tanaji
authors.initials: ST
authors.lastname: Mundhe
authors.affiliation: Department of Urology, Lokmanya Tilak Municipal Medical College and General Hospital, Mumbai, Maharastra, India.
authors.forename: Sayalee Suryabhan
authors.initials: SS
authors.lastname: Narwade
authors.affiliation: Department of Urology, Lokmanya Tilak Municipal Medical College and General Hospital, Mumbai, Maharastra, India.
authors.forename: Ashwin Sunil
authors.initials: AS
authors.lastname: Tamhankar
keywords: Creatinine clearance; diethylene-triamine-penta-acetic acid scan; glomerular filtration rate; percutaneous nephrostomy; percutaneous nephrostomy creatinine clearance