title: Prospective study of the extent of internal anal sphincter division during lateral sphincterotomy.
abstract: OBJECTIVE
  The aim of lateral internal anal sphincterotomy when treating anal fissure is to divide the distal one-third to one-half of the internal anal sphincter. This study aimed to evaluate prospectively the extent of disruption to the internal anal sphincter following lateral anal internal sphincterotomy and also to establish the prevalence of symptoms of anal incontinence in these patients.
  
  
  METHODS
  Fifteen patients with anal fissure (ten females and five males) had bowel symptoms assessed and anal endosonography performed preoperatively and two months after lateral internal anal sphincterotomy.
  
  
  RESULTS
  Anal endosonography was normal preoperatively in all but two females who had anterior external sphincter defects (presumedly from previous obstetric trauma). Postoperatively, apart from one male in whom no defect could be identified, all had an internal anal sphincter defect corresponding to the site of lateral internal anal sphincterotomy. In nine of the ten females, the defect involved the full length of the internal anal sphincter, but in the other four males, the defect involved the distal internal anal sphincter only. All were continent preoperatively, but after lateral internal anal sphincterotomy, three females became incontinent to flatus (two of whom had a preoperative external sphincter defect).
  
  
  CONCLUSIONS
  In contrast to lateral internal anal sphincterotomy in males, division of the internal anal sphincter in most females tends to be more extensive than intended. This is probably related to their shorter anal canal. In some females, lateral internal anal sphincterotomy may compromise sphincter function and precipitate anal incontinence, particularly in the presence of other sphincter defects. Care should be exercised especially in the presence of previous obstetric trauma, as internal anal sphincter division may further compromise sphincter function.
authors.affiliation: Department of Physiology, St. Mark's Hospital, London, United Kingdom.
authors.forename: A H
authors.initials: AH
authors.lastname: Sultan
authors.forename: M A
authors.initials: MA
authors.lastname: Kamm
authors.forename: R J
authors.initials: RJ
authors.lastname: Nicholls
authors.forename: C I
authors.initials: CI
authors.lastname: Bartram
mesh_terms: D000328:Adult; D000368:Aged; D001003:Anal Canal / Q000000981:diagnostic imaging / Q000601:surgery*; D005242:Fecal Incontinence / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D005401:Fissure in Ano / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010298:Parity; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000209:etiology; D011300:Preoperative Care; D015995:Prevalence; D011446:Prospective Studies; D012737:Sex Factors; D013514:Surgical Procedures, Operative / Q000379:methods; D016896:Treatment Outcome; D014463:Ultrasonography