title: Supranormal renal function in unilateral hydronephrotic kidney can be avoided.
abstract: BACKGROUND
  There are reports and controversy in the literature of supranormal (defined as >55%) differential renal function (DRF) in the hydronephrotic kidney in children with unilateral hydronephrosis. It is not confirmed whether supranormal DRF is an artifact or a true finding. In patients in whom the relative renal function deteriorates, relief of obstruction becomes surgically necessary and if this artifact can be removed. Supranormal function in an obstructed kidney is confusing and there is no consensus on how to manage these patients. There is no agreement if this is a true entity or an artifact. We wanted to address this issue by reporting our experience.
  
  
  METHODS
  We reviewed all the consecutive cases from August 2000 to October 2001 who were studied in our center with the diagnosis of unilateral renal obstruction for confirmation or evaluation of DRF. All patients had MAG-3 studies that were interpreted by experienced nuclear medicine physicians. The DRF were measured within the first to second minute of the MAG-3 injection. Regions of interest were drawn by the imaging software and the images were corrected for background counts by drawing regions of interest 2 pixels away from the edge of the renal cortex.
  
  
  RESULTS
  Fifty-seven patients were confirmed to be obstructed unilaterally; 41 (72%) patients had obstructive lesions in the left kidney and 16 (28%) in the right kidney. There was no case of supranormal DRF in the obstructed kidneys in our study.
  
  
  CONCLUSIONS
  The supranormal renal function, as noted in some reports in the literature, was not seen in any patients at our institution. We believe that this entity is an artifact and can be avoided by using MAG-3 and projecting regions of interest by computer software; we plan to start analyzing multiple algorithms in phantoms with different ROI selection for background analysis.
authors.affiliation: Department of Nuclear Medicine, Hospital University of Pennsylvania, Philadelphia. 19104, USA.
authors.forename: Jehanzeb
authors.initials: J
authors.lastname: Khan
authors.forename: Martin
authors.initials: M
authors.lastname: Charron
authors.forename: Marc P
authors.initials: MP
authors.lastname: Hickeson
authors.forename: Roberto
authors.initials: R
authors.lastname: Accorsi
authors.forename: S
authors.initials: S
authors.lastname: Qureshi
authors.forename: Douglas
authors.initials: D
authors.lastname: Canning
mesh_terms: D016477:Artifacts; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006869:Hydronephrosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D007091:Image Processing, Computer-Assisted; D007223:Infant; D007668:Kidney / Q000000981:diagnostic imaging* / Q000503:physiopathology; D007672:Kidney Cortex / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D011866:Radioisotope Renography; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D012984:Software; D017263:Technetium Tc 99m Mertiatide; D014517:Ureteral Obstruction / Q000000981:diagnostic imaging / Q000503:physiopathology
chemical_list: D019275:Radiopharmaceuticals; D017263:Technetium Tc 99m Mertiatide