title: Measurement of Differential Renal Function by Scintigraphy in Hydronephrotic Kidneys: Importance of Conjugate Views for Accurate Evaluation.
abstract: OBJECTIVE
  Traditionally a single posterior view is used to measure differential renal function during nuclear renal scintigraphy. Nevertheless, experimental data show important variation in this measurement in the setting of significant hydronephrosis. To date, the impact of degree of hydronephrosis on the accuracy of differential renal function determination has not been addressed. We evaluated the discrepancy between function measured by anterior and posterior views, and the relationship to varying degrees of hydronephrosis.
  
  
  METHODS
  We retrospectively reviewed consecutive mercaptoacetyltriglycine renal scans from 2009 to 2011. Ultrasounds were reviewed and degree of hydronephrosis was recorded using anteroposterior pelvic diameter. Absolute percent difference in differential renal function between each view (anterior minus posterior) was calculated and correlated to anteroposterior pelvic diameter. Patients were stratified into 4 groups according to anteroposterior pelvic diameter, ie less than 10 mm, greater than 10 mm, greater than 15 mm and greater than 25 mm.
  
  
  RESULTS
  A total of 519 scans with corresponding ultrasounds were analyzed. Median patient age was 2.26 years. Kidneys with a larger anteroposterior pelvic diameter had a greater discrepancy in function on anterior and posterior views. There was a meaningful discrepancy for anteroposterior pelvic diameter greater than 10 mm (p = 0.034) and greater than 25 mm (p = 0.032). Several statistical models were used to identify a meaningful cut point of 15 mm, where the discrepancy in anterior and posterior views became significant (p = 0.001).
  
  
  CONCLUSIONS
  The use of single views during nuclear renography for grossly hydronephrotic kidneys is often inaccurate. The discrepancy in differential renal function obtained on the anterior and posterior views is adversely impacted especially as anteroposterior pelvic diameter increases beyond 15 mm. Therefore, we suggest incorporation of conjugate views for estimating differential renal function in patients with hydronephrosis.
authors.affiliation: Children's Hospital of Orange County, Orange, California; University of California Irvine Medical Center, Orange, California.
authors.forename: Elias
authors.initials: E
authors.lastname: Wehbi
authors.affiliation: Division of Urology, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.
authors.forename: Ana
authors.initials: A
authors.lastname: Salle
authors.affiliation: Division of Urology, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.
authors.forename: Niki
authors.initials: N
authors.lastname: Kanaroglou
authors.affiliation: Division of Urology, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.
authors.forename: Armando
authors.initials: A
authors.lastname: Lorenzo
authors.affiliation: Division of Urology, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.
authors.forename: Darius
authors.initials: D
authors.lastname: Bagli
authors.affiliation: Division of Urology, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Koyle
authors.affiliation: University of California Irvine Medical Center, Orange, California.
authors.forename: John
authors.initials: J
authors.lastname: Billimek
authors.affiliation: Division of Nuclear Medicine, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.
authors.forename: Reza
authors.initials: R
authors.lastname: Vali
authors.affiliation: Division of Nuclear Medicine, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Charron
authors.affiliation: Division of Urology, Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada. Electronic address: psalle@sidra.org.
authors.forename: Joao Luiz
authors.initials: JL
authors.lastname: Pippi Salle
mesh_terms: D002675:Child, Preschool; D005260:Female; D006801:Humans; D006869:Hydronephrosis / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D007223:Infant; D007231:Infant, Newborn; D007677:Kidney Function Tests; D008297:Male; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D017263:Technetium Tc 99m Mertiatide; D014463:Ultrasonography
chemical_list: D019275:Radiopharmaceuticals; D017263:Technetium Tc 99m Mertiatide
keywords: hydronephrosis; kidney function tests; pediatrics; radionuclide imaging; technetium Tc 99m mertiatide