title: Value of hydrogen peroxide enhancement of three-dimensional endoanal ultrasound in fistula-in-ano.
abstract: OBJECTIVE
  The aim of this prospective study was to compare the accuracy of three-dimensional endoanal ultrasound with that of hydrogen peroxide enhanced three-dimensional endoanal ultrasound in diagnosing recurrent or complex fistula-in-ano.
  
  
  METHODS
  Three-dimensional endoanal ultrasound reconstructions were performed before and after hydrogen peroxide enhancement in 19 patients with suspected recurrent or complex fistula-in-ano. Two experienced observers derived a consensus fistula classification after a blinded random review of the data sets. The accuracy of three-dimensional endoanal ultrasound and that of hydrogen peroxide-enhanced three-dimensional endoanal ultrasound were compared with a reference standard derived from surgical findings and magnetic resonance imaging and modified by outcome over a median follow-up of 13 months.
  
  
  RESULTS
  Patients had previously undergone a median of three fistula operations. Four had Crohn's disease. There were 21 internal openings and primary tracks in 19 patients: 1 superficial, 1 intersphincteric, 18 transsphincteric, and 1 extrasphincteric. Fourteen patients had 19 secondary tracks. Both techniques detected fistula tracks in 19 of 21 (90 percent) patients. There was no significant difference between three-dimensional endoanal ultrasound and hydrogen peroxide-enhanced three-dimensional endoanal ultrasound in classifying internal openings (19/21 (90 percent) vs. 18/21 (86 percent)), primary tracks (17/21 (81 percent) vs. 15/21 (71 percent)), or secondary tracks (13/19 (68 percent) vs. 12/19 (63 percent)). Where three-dimensional endoanal ultrasound correctly detected an internal opening, gas from hydrogen peroxide enhancement was present in 8 of 18 (44 percent) studies. Similarly, gas made primary tracks more conspicuous in 6 of 19 (32 percent) and secondary tracks in 6 of 13 (46 percent) of those detected.
  
  
  CONCLUSIONS
  In recurrent or complex fistula-in-ano, endoanal ultrasound proved more accurate for detecting primary tracks and internal openings than for detecting extensions. Hydrogen peroxide improved conspicuity of some tracks and internal openings and so may be helpful in difficult cases, although no overall diagnostic benefit was demonstrated.
authors.affiliation: Department of Surgery, St. Mark's Hospital, London, United Kingdom.
authors.forename: Gordon N
authors.initials: GN
authors.lastname: Buchanan
authors.forename: Clive I
authors.initials: CI
authors.lastname: Bartram
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Williams
authors.forename: Steve
authors.initials: S
authors.lastname: Halligan
authors.forename: C Richard G
authors.initials: CR
authors.lastname: Cohen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019160:Endosonography / Q000379:methods*; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage*; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D016877:Oxidants / Q000008:administration & dosage*; D011300:Preoperative Care; D012003:Rectal Fistula / Q000000981:diagnostic imaging*; D012680:Sensitivity and Specificity
chemical_list: D016877:Oxidants; D006861:Hydrogen Peroxide