title: Intermittent hydronephrosis secondary to ureteropelvic junction obstruction: clinical and imaging features.
abstract: OBJECTIVE
  We sought to assess the clinical and imaging findings in intermittent hydronephrosis secondary to ureteropelvic junction obstruction, with particular emphasis on the characteristic ultrasonographic findings.
  
  
  METHODS
  This prospective, longitudinal, observational study included all children who had intermittent ureteropelvic junction obstruction and presented with abdominal pain over 6 years. Renal ultrasound was used as an initial screening tool to detect intermittent hydronephrosis. Renal ultrasonography was repeated every 1 to 2 days to record serial changes from the symptomatic to the asymptomatic stage. Their clinical manifestations and imaging findings were studied.
  
  
  RESULTS
  Eighteen patients (14 boys, 4 girls) were studied. Most had sharp pain that began acutely and typically lasted for <2 days. Most of the children (16 of 18) had nausea and vomiting that accompanied the pain. The acute episode generally resolved spontaneously and was followed by a pain-free interval that ranged from days to months. Factors that predisposed to an attack included increased water intake, vigorous exercise, or bladder distention. All patients had clearly demonstrable obstruction of the renal pelvis during an acute attack, a finding that diminished or resolved during the symptom-free intervals. During convalescence, all patients had renal pelvic wall thickening on ultrasonography. This finding appeared on the second or third day after a painful episode subsided, persisted for 6 to 9 days, and then disappeared in the symptom-free stage. Pyeloplasty was performed in 17 patients, none of whom had recurrent pain on follow-up. Extrinsic obstructions were found in 9 patients.
  
  
  CONCLUSIONS
  The keys to diagnosis are awareness of the syndrome, a detailed history, and immediate and serial imaging studies during painful crises. A thickened renal pelvic wall during convalescence is an important ultrasonic sign of intermittent hydronephrosis.
authors.affiliation: Department of Pediatrics, Mackay Memorial Hospital, Taipei, Taiwan.
authors.forename: Jeng-Daw
authors.initials: JD
authors.lastname: Tsai
authors.forename: Fu-Yuan
authors.initials: FY
authors.lastname: Huang
authors.forename: Chun-Chen
authors.initials: CC
authors.lastname: Lin
authors.forename: Tsuen-Chiuan
authors.initials: TC
authors.lastname: Tsai
authors.forename: Hung-Chang
authors.initials: HC
authors.lastname: Lee
authors.forename: Jin-Cherng
authors.initials: JC
authors.lastname: Sheu
authors.forename: Pei-Yeh
authors.initials: PY
authors.lastname: Chang
mesh_terms: D000006:Abdomen, Acute / Q000209:etiology; D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006869:Hydronephrosis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000209:etiology; D007668:Kidney / Q000000981:diagnostic imaging; D007682:Kidney Pelvis / Q000000981:diagnostic imaging; D008297:Male; D011866:Radioisotope Renography; D012008:Recurrence; D014463:Ultrasonography; D014517:Ureteral Obstruction / Q000150:complications / Q000175:diagnosis* / Q000000981:diagnostic imaging