title: Drainage-related ultrasonography (DRUS): a novel technique for discriminating obstructive and nonobstructive hydroureters in children.
abstract: BACKGROUND
  Despite advances in urologic imaging, the paucity of an optimal technique that accurately clarifies obstructive and nonobstructive hydroureter exists.
  
  
  OBJECTIVE
  This study was conducted to introduce a novel and modified ultrasonographic technique, known as drainage-related ultrasonography (DRUS), discriminating obstructive and nonobstructive, nonrefluxing hydroureter.
  
  
  METHODS
  A total of 358 children (mean age, 3.7 years) with 418 nonrefluxing hydroureter were included. These children were composed of two groups of obstructive nonrefluxing (141 children with 157 dilated ureters) and nonobstructive, nonrefluxing (217 children with 261 hydroureter). The definite diagnosis regarding the subtype of hydroureter was derived from appropriate investigation. The maximum diameter of the dilated ureter, which was observed on ultrasonography, was recorded before and after 3 h of catheterization, as D1 and D2, respectively. To assess the D ratio, a formula was developed, that is, [(|D1 - D2|)/D1] × 100. Values were recorded and cutoff points were set to discriminate between subtypes.
  
  
  RESULTS
  Obstructive versus nonobstructive subtypes of nonrefluxing hydroureter were clarified with 78.5 % sensitivity and 83.4 % specificity, by setting a cutoff point of 22 % for the D ratio. Regardless of the cutoff point assigned to the reduction in D (D2 compared with D1), DRUS revealed 93.9 % sensitivity, 80.6 % specificity, 63.2 % positive predictive value, and 97.4 % negative predictive value in discriminating upper from lower obstruction.
  
  
  CONCLUSIONS
  DRUS affords favorable results in terms of differentiating between obstructive and nonobstructive, nonrefluxing hydroureter, as well as between upper and lower obstruction in obstructive cases. It has the potential to become an efficient imaging modality in the diagnostic algorithm of hydroureter.
authors.affiliation: Pediatric Urology Research Center, Pediatric Center of Excellence, Tehran University of Medical Sciences, No. 32, 2nd Floor, 7th Street Saadat-Abad Ave, Tehran, 1998714616 Iran.
authors.forename: Abdol-Mohammad
authors.initials: AM
authors.lastname: Kajbafzadeh
authors.affiliation: Pediatric Radiology Department, Pediatric Center of Excellence, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mehrzad
authors.initials: M
authors.lastname: Mehdizadeh
authors.affiliation: Pediatric Urology Research Center, Pediatric Center of Excellence, Tehran University of Medical Sciences, No. 32, 2nd Floor, 7th Street Saadat-Abad Ave, Tehran, 1998714616 Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Aryan
authors.affiliation: Pediatric Urology Research Center, Pediatric Center of Excellence, Tehran University of Medical Sciences, No. 32, 2nd Floor, 7th Street Saadat-Abad Ave, Tehran, 1998714616 Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Ebadi
authors.affiliation: Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Boston, MA USA.
authors.forename: Shadi Abdar
authors.initials: SA
authors.lastname: Esfahani
authors.affiliation: Pediatric Urology Research Center, Pediatric Center of Excellence, Tehran University of Medical Sciences, No. 32, 2nd Floor, 7th Street Saadat-Abad Ave, Tehran, 1998714616 Iran.
authors.forename: Laleh
authors.initials: L
authors.lastname: Montaser-Kouhsari
authors.affiliation: Division of Abdominal Imaging and Interventional Radiology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, White 270, Boston, MA 02114 USA.
authors.forename: Azadeh
authors.initials: A
authors.lastname: Elmi
authors.affiliation: Division of Abdominal Imaging and Interventional Radiology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, White 270, Boston, MA 02114 USA.
authors.forename: Saman Shafaat
authors.initials: SS
authors.lastname: Talab
authors.affiliation: Department of Urology, University Hospitals of Case Medical Center, Case Western Reserve University, Cleveland, OH 44106 USA.
authors.forename: Zhina
authors.initials: Z
authors.lastname: Sadeghi
keywords: Drainage; Hydroureter; Radioisotope renography; Technetium-99 m DTPA; Urinary bladder; Urinary tract obstruction