title: Comparison of hydrogen peroxide instillation with Goodsall's rule for fistula-in-ano.
abstract: BACKGROUND
  Identification of the internal opening is an essential step in the management of fistula-in-ano. The predictive accuracy of Goodsall's rule is compared with instillation of hydrogen peroxide for fistulas-in-ano.
  
  
  METHODS
  Thirty-five patients (32 male, three female; median age 42 years; range: 6 months-70 years) were studied. Hydrogen peroxide solution was injected into the external opening of the fistula track and effervescence was observed at the internal opening within the anal canal. A fistula track was either excised or incised. Setons were placed within high fistulas.
  
  
  RESULTS
  There were 24 simple fistulas, compared to 11 complex fistulas (horseshoe, n = 4; abscess, n = 4). Eighteen external openings were anterior and 17 were posterior. Thirty-four of 35 (97%) internal openings were identified. Only 20 internal openings were in accordance with Goodsall's rule (positive predictive value: 59%). Predictive accuracy was greater for anterior external openings (13 of 18 (72%)) versus posterior external openings (six of 17 (41%); P = 0.016). For recurrent fistulas, seven of 17 fistula tracks had an internal opening in accordance with Goodsall's rule, resulting in a positive predictive value of 41%. (Positive predictive value: anterior 67% vs posterior 12.5%; P = 0.0009.)
  
  
  CONCLUSIONS
  The overall predictive accuracy of Goodsall's rule was poor chiefly because of poor predictive accuracy in posterior and recurrent fistulas. The use of Goodsall's rule alone in decision-making before surgical intervention is not recommended.
authors.affiliation: University Department of Surgery, North Colombo General Hospital,  Sri Lanka.
authors.forename: P A
authors.initials: PA
authors.lastname: Gunawardhana
authors.forename: K I
authors.initials: KI
authors.lastname: Deen
mesh_terms: D000285:Administration, Rectal; D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003938:Diagnostic Techniques, Digestive System; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage*; D007223:Infant; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012003:Rectal Fistula / Q000175:diagnosis* / Q000601:surgery; D012007:Rectum / Q000473:pathology / Q000601:surgery
chemical_list: D006861:Hydrogen Peroxide