title: Internal anal sphincter: Clinical perspective.
abstract: OBJECTIVE
  To summarise current knowledge of Internal anal sphincter.
  
  
  BACKGROUND
  The internal anal sphincter (IAS) is the involuntary ring of smooth muscle in the anal canal and is the major contributor to the resting pressure in the anus. Structural injury or functional weakness of the muscle results in passive incontinence of faeces and flatus. With advent of new assessment and treatment modalities IAS has become an important topic for surgeons. This review was undertaken to summarise our current knowledge of internal anal sphincter and highlight the areas that need further research.
  
  
  METHODS
  The PubMed database was used to identify relevant studies relating to internal anal sphincter.
  
  
  RESULTS
  The available evidence has been summarised and advantages and limitations highlighted for the different diagnostic and therapeutic techniques.
  
  
  CONCLUSIONS
  Our understanding of the physiology and pharmacology of IAS has increased greatly in the last three decades. Additionally, there has been a rise in diagnostic and therapeutic techniques specifically targeting the IAS. Although these are promising, future research is required before these can be incorporated into the management algorithm.
authors.affiliation: GI Physiology Unit, University College Hospital, London, UK. Electronic address: l.kumar@ucl.ac.uk.
authors.forename: Lalit
authors.initials: L
authors.lastname: Kumar
authors.affiliation: GI Physiology Unit, University College Hospital, London, UK; University College London, UK. Electronic address: a.emmanuel@ucl.ac.uk.
authors.forename: Anton
authors.initials: A
authors.lastname: Emmanuel
mesh_terms: D001003:Anal Canal / Q000033:anatomy & histology / Q000293:injuries / Q000473:pathology / Q000503:physiopathology; D005242:Fecal Incontinence / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000628:therapy; D006801:Humans
keywords: Anal sphincter; IAS; Internal anal sphincter; Internal sphincter