title: Incidence and implications of silent hydronephrosis following percutaneous nephrolithotomy .
abstract: OBJECTIVE
  While routine renal imaging following ureteroscopy for urinary calculi has been recommended to screen for asymptomatic "silent" obstruction, the rate of silent obstruction following percutaneous nephrolithotomy (PCNL) remains poorly defined, and no consensus recommendations exist on routine postoperative imaging. At our institution, we sought to assess the incidence of silent hydronephrosis (SH), as a screen for obstruction, following PCNL.
  
  
  METHODS
  The records of all 162 patients who met study inclusion criteria were reviewed. Of this group, 112 patients presented for their scheduled renal ultrasonography 4 - 6 weeks following stent removal to screen for SH. Asymptomatic patients found to have ultrasonographic evidence of hydronephrosis were further analyzed.
  
  
  RESULTS
  SH was noted in 16% (18/112) of patients. Two required subsequent ureteroscopic stone extraction (1.8%), one of which also underwent endoureterotomy for a ureteral stricture. Four patients (22%) had stable hydronephrosis and declined functional imaging, 2 patients (11%) had a known partial ureteropelvic junction obstruction and declined intervention. SH resolved spontaneously in 50% (9/18) with a mean time to resolution of 6.3 months. There was no difference in stone complexity based on Guy's stone score between groups, 2.8 (± 0.92) vs. 2.4 (± 1.03), p = 0.34. Although not statistically significant, patients with SH were more likely to have had residual stone fragments postoperatively, 39% (7/18) vs. 19% (18/94), p = 0.067.
  
  
  CONCLUSIONS
  SH following, PCNL was identified in 16% of this screened population, with the majority requiring no intervention. However, SH may be attributed to residual stone or stricture, which may have been otherwise unrecognized in up to 2% of patients undergoing PCNL. Consideration should be given for routine postoperative ultrasound to screen for silent obstruction following PCNL. .
authors.forename: Lawrence
authors.initials: L
authors.lastname: Dagrosa
authors.forename: Rachel
authors.initials: R
authors.lastname: Moses
authors.forename: Vernon M
authors.initials: VM
authors.lastname: Pais
mesh_terms: D000328:Adult; D000368:Aged; D058070:Asymptomatic Diseases; D005260:Female; D006801:Humans; D006869:Hydronephrosis / Q000000981:diagnostic imaging* / Q000209:etiology / Q000628:therapy; D008297:Male; D008875:Middle Aged; D009403:Nephrostomy, Percutaneous / Q000009:adverse effects*; D011183:Postoperative Complications / Q000000981:diagnostic imaging* / Q000209:etiology / Q000628:therapy; D012189:Retrospective Studies; D014463:Ultrasonography; D014514:Ureteral Calculi / Q000150:complications / Q000601:surgery; D014517:Ureteral Obstruction / Q000000981:diagnostic imaging* / Q000209:etiology / Q000628:therapy; D018666:Ureteroscopy