title: Use of Contrasted Computerized Tomography as a Surrogate for Nuclear Medicine Renogram to Categorize Renal Function in the Setting of Ureteropelvic Junction Obstruction.
abstract: OBJECTIVE
  To use basic measurements on contrasted computerized tomography (CT) to reliably determine whether a kidney with ureteropelvic junction obstruction (UPJO) is definitively functional (≥30% differential renal function [DRF]) or nonfunctional (≤10% DRF), obviating the need for nuclear medicine renogram (RG) to determine DRF.
  
  
  METHODS
  This is a single institution, retrospective cohort of patients diagnosed with UPJO who underwent either pyeloplasty or nephrectomy between December 2004 and December 2014. Included patients had both preoperative mercaptoacetyltriglycine RG and contrasted CT within 180 days of each other. Patients with stents or nephrostomy tubes were excluded.
  
  
  RESULTS
  A total of 49 patients were included. The strongest correlation between differential CT measurements and DRF on RG existed by multiplying the cortical area by the average cortical Hounsfield units (Pearson's r = 0.90, P < .001). Using an equation derived from linear regression and cutoff values generated by receiver operator curve (ROC) analysis, CT equation-estimated DRF values of ≥40% and ≤10% correlated with "definitively functional" RG values of ≥30% (100% specificity) and with "definitively nonfunctional" RG values of ≤10% (100% specificity), respectively. In 30 out of 49 cases, CT could have replaced RG.
  
  
  CONCLUSIONS
  RG is the gold standard in determining quantitative DRF. However, the treatment algorithm for a kidney with symptomatic UPJO hinges on categorized function: "functional" (repair) or "nonfunctional" (remove). Appropriate measurements on contrasted CT can categorize definitively functional or nonfunctional kidneys with UPJO, negating the need for RG to obtain DRF in a majority of cases. This study design favors real-world application with potential to reduce medical expenditure and delay in definitive treatment.
authors.affiliation: Department of Urologic Surgery, Vanderbilt University Medical Center, Nashville, TN. Electronic address: Jacob.ark@vanderbilt.edu.
authors.forename: Jacob T
authors.initials: JT
authors.lastname: Ark
authors.affiliation: Department of Urologic Surgery, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Mitchell
authors.affiliation: Department of Urologic Surgery, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: Tracy P
authors.initials: TP
authors.lastname: Marien
authors.affiliation: Department of Urologic Surgery, Vanderbilt University Medical Center, Nashville, TN.
authors.forename: S Duke
authors.initials: SD
authors.lastname: Herrell
mesh_terms: D000328:Adult; D000368:Aged; D003287:Contrast Media; D005260:Female; D006801:Humans; D007677:Kidney Function Tests; D007682:Kidney Pelvis / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy; D012372:ROC Curve; D011866:Radioisotope Renography; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014513:Ureter / Q000000981:diagnostic imaging; D014517:Ureteral Obstruction / Q000000981:diagnostic imaging* / Q000503:physiopathology* / Q000601:surgery; D055815:Young Adult
chemical_list: D003287:Contrast Media