title: Contradictory supranormal function in hydronephrotic kidneys: fact or artifact on pediatric MAG-3 renal scans?
abstract: OBJECTIVE
  Contradictory supranormal renal function (SRF) in unilateral hydronephrosis is a debatable subject resulting from the methodology of nuclear renography or the characteristics of the patient. In this study, we aimed to investigate the frequency and comparison of SRF with MAG-3 scans by 8 different technical analyses in pediatric hydronephrosis.
  
  
  METHODS
  We reviewed Tc-99m MAG-3 scans in 82 children with unilateral hydronephrosis (52 male, 30 female, mean age: 47.7 +/- 64.5 months). Of 82, 34 also had Tc-99m DMSA scans. Data were reprocessed with 4 different regions of background activity (subrenal, perirenal C-type, perirenal ring, and lateral) at 2 different time intervals (1-2 and 2-3 minute), and 8 different estimates of MAG-3 differential renal function (DRF) were obtained in 67 patients. SRF was defined as DRF greater than 55% in the hydronephrotic kidney.
  
  
  RESULTS
  The routine processing protocol showed only 3 renal units with SRF, and all were on the right side (3.6%). After reprocessing, a total of 10 dilated kidneys had SRF in 1 or more of DRF estimates (5.2% of all estimations). These cases were significantly younger (8.1 +/- 6.7 vs. 42.5 +/- 52.5, P < 0.05) and had a larger renal area ratio (1.25 +/- .24 vs. 1.07 +/- .21, P < 0.05). There was no SRF with DMSA. In comparison between MAG-3 and DMSA DRF in 20 children who underwent both tests within 3 months, the best correlation was obtained when C-type correction was used for both agents at 2 time intervals (r: .86 and .84 for early and late time intervals, P < 0.00001, respectively).
  
  
  CONCLUSIONS
  SRF in unilateral hydronephrosis is, at least, in part, technical in origin in this particular pediatric patient population with tubular immaturity (ie, physiological high background activity) and asymmetric kidney size.
authors.affiliation: Nuclear Medicine, Marmara University, School of Medicine, Altunizade-Istanbul, Turkey. sinanir@marmara.edu.tr
authors.forename: Sabahat
authors.initials: S
authors.lastname: Inanir
authors.forename: Nese
authors.initials: N
authors.lastname: Biyikli
authors.forename: Omid
authors.initials: O
authors.lastname: Noshari
authors.forename: Billur
authors.initials: B
authors.lastname: Caliskan
authors.forename: Halil
authors.initials: H
authors.lastname: Tugtepe
authors.forename: Tanju Yusuf
authors.initials: TY
authors.lastname: Erdil
authors.forename: Ihsan
authors.initials: I
authors.lastname: Akpinar
authors.forename: Gursu
authors.initials: G
authors.lastname: Kiyan
authors.forename: Harika
authors.initials: H
authors.lastname: Alpay
mesh_terms: D000293:Adolescent; D016477:Artifacts; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D019317:Evidence-Based Medicine / Q000379:methods; D005260:Female; D006801:Humans; D006869:Hydronephrosis / Q000000981:diagnostic imaging*; D015994:Incidence; D007223:Infant; D007668:Kidney / Q000000981:diagnostic imaging*; D008297:Male; D011866:Radioisotope Renography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D017263:Technetium Tc 99m Mertiatide
chemical_list: D019275:Radiopharmaceuticals; D017263:Technetium Tc 99m Mertiatide