title: Peroxide-enhanced endoanal ultrasound in preoperative assessment of complex fistula-in-ano.
abstract: BACKGROUND
  In complex fistula-in-ano, preoperative imaging can help identify secondary tracts and abscesses that can be missed, leading to recurrence. We evaluated hydrogen peroxide-enhanced endoanal ultrasound (PEEUS) in the characterization of fistula compared with standard clinical and operative assessment.
  
  
  METHODS
  Patients with complex fistula-in-ano treated between February 2008 and May 2009 at our institution were prospectively evaluated by PEEUS with recording of the preoperative clinical examination and intraoperative details of the fistula. Of the 135 patients with fistula-in-ano, 68 met the inclusion criteria for complex fistula-in-ano. Correlation of clinical findings and PEEUS to the gold standard intraoperative findings was assessed in characterizing the fistula. The percent agreement between the clinical and PEEUS findings against the gold standard was derived, and the kappa statistic for agreement was determined.
  
  
  RESULTS
  The mean age of the cohort was 42.54 ± 10.86 years. The fistula tracts were curvilinear, high, and transsphincteric in 16 (23.53%), 8 (11.76%), and 42 (61.76%) patients, respectively. Secondary tracts and associated abscess cavities were seen in 28 (33.82%) and 35 (51.47%) patients, respectively. PEEUS correlated better than clinical examination with regard to site (92.65 vs 79.41%; p < 0.001) and course (91.18 vs 77.94%; p < 0.001) of secondary tract and associated abscesses (89.71 vs 80.88%; p = 0.02). There was a trend of better correlation of PEEUS compared to clinical examination in classifying the primary tract as per Park's system (88.24 vs 79.41%; p = 0.06), but it did not reach statistical significance. PEEUS and clinical examination were comparable in correlation of the level of the primary tract (kappa: 0.86 vs 0.78; p = 0.22) and the site of internal opening (kappa: 0.97 vs 0.89; p = 0.22). The operative decision was changed in 13 (19.12%) subjects based on PEEUS findings.
  
  
  CONCLUSIONS
  PEEUS is a feasible and efficient tool in the routine preoperative assessment of complex fistula-in-ano.
authors.affiliation: Colorectal Unit, Department of Surgical Gastroenterology, Global Hospitals, Hyderabad, Andhra Pradesh, India.
authors.forename: C
authors.initials: C
authors.lastname: Nagendranath
authors.forename: M N
authors.initials: MN
authors.lastname: Saravanan
authors.forename: C
authors.initials: C
authors.lastname: Sridhar
authors.forename: M
authors.initials: M
authors.lastname: Varughese
mesh_terms: D000328:Adult; D019160:Endosonography / Q000379:methods*; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide; D007194:India; D008297:Male; D008875:Middle Aged; D010808:Physical Examination; D011300:Preoperative Care / Q000379:methods*; D011446:Prospective Studies; D012003:Rectal Fistula / Q000000981:diagnostic imaging* / Q000601:surgery
chemical_list: D006861:Hydrogen Peroxide
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