title: Obstructive vs nonobstructive dilatation of the renal collecting system in children: distinction with duplex sonography.
abstract: OBJECTIVE
  The resistive index in cortical or arcuate renal arteries of children was calculated to determine whether obstructive uropathy could be differentiated from nonobstructive dilatation.
  
  
  METHODS
  Kidneys (n = 176) were prospectively evaluated by using duplex Doppler sonography in patients 3 days to 20 years old. Obstruction was confirmed by renography with furosemide and/or by surgery.
  
  
  RESULTS
  The normal resistive index was 0.57 +/- 0.06 and the normal difference in resistive indexes between kidneys was 0.03 +/- 0.02 (n = 15). Abnormal values indicative of ureteropelvic junction obstruction were defined as the normal mean +/- 2 SD (i.e., a resistive index of > or = 0.70 plus a difference in resistive indexes between kidneys of > or = 0.08). Patients with unilateral dilatation and obstruction at the ureteropelvic junction (n = 20) had a mean resistive index of 0.77 +/- 0.05 and a difference in resistive indexes between kidneys of 0.16 +/- 0.05 (p < .001 compared with patients with normal kidneys and p < .001 compared with patients with unilateral dilatation without obstruction). Patients with unilateral dilatation but without obstruction (n = 16) had a mean resistive index of 0.63 +/- 0.06 and a difference between kidneys of 0.06 +/- 0.04 (values within normal limits). The positive and negative predictive values of the obstruction criteria for unilateral collecting system dilatation were 95% and 100%, respectively. After successful surgical correction of ureteropelvic junction obstruction (n = 29), patients had a normal mean resistive index of 0.61 +/- 0.05 and a normal difference between kidneys of 0.03 +/- 0.03. Five patients examined both before and after surgery showed a statistically significant drop in the resistive index of the obstructed kidney (0.75 +/- 0.03 to 0.65 +/- 0.05, p < .05) after surgery and a small rise in the resistive index of the contralateral kidney (0.56 +/- 0.04 to 0.63 +/- 0.04, p < .02).
  
  
  CONCLUSIONS
  The resistive index appears to be an effective parameter for the evaluation and follow-up of unilateral obstructive or nonobstructive ureteropelvic junction dilatation in children.
authors.affiliation: Department of Radiology, Miami Children's Hospital, FL 33155.
authors.forename: R M
authors.initials: RM
authors.lastname: Kessler
authors.forename: H
authors.initials: H
authors.lastname: Quevedo
authors.forename: C A
authors.initials: CA
authors.lastname: Lankau
authors.forename: F
authors.initials: F
authors.lastname: Ramirez-Seijas
authors.forename: A
authors.initials: A
authors.lastname: Cepero-Akselrad
authors.forename: D H
authors.initials: DH
authors.lastname: Altman
authors.forename: K M
authors.initials: KM
authors.lastname: Kessler
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004108:Dilatation, Pathologic; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007668:Kidney / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D011866:Radioisotope Renography; D014463:Ultrasonography; D014517:Ureteral Obstruction / Q000000981:diagnostic imaging*