title: The effect of luminal content and rate of occlusion on the interpretation of colonic manometry.
abstract: BACKGROUND
  Manometry is commonly used for diagnosis of esophageal and anorectal motility disorders. In the colon, manometry is a useful tool, but clinical application remains uncertain. This uncertainty is partly based on the belief that manometry cannot reliably detect non-occluding colonic contractions and, therefore, cannot identify reliable markers of dysmotility. This study tests the ability of manometry to record pressure signals in response to non-lumen-occluding changes in diameter, at different rates of wall movement and with content of different viscosities.
  
  
  METHODS
  A numerical model was built to investigate pressure changes caused by localized, non-lumen-occluding reductions in diameter, similar to those caused by contraction of the gut wall. A mechanical model, consisting of a sealed pressure vessel which could produce localized reductions in luminal diameter, was used to validate the model using luminal segments formed from; (i) natural latex; and (ii) sections of rabbit proximal colon. Fluids with viscosities ranging from 1 to 6800 mPa s(-1) and luminal contraction rates over the range 5-20 mmHg s(-1) were studied.
  
  
  RESULTS
  Manometry recorded non-occluding reductions in diameter, provided that they occurred with sufficiently viscous content. The measured signal was linearly dependent on the rate of reduction in luminal diameter and also increased with increasing viscosity of content (R(2) = 0.62 and 0.96 for 880 and 1760 mPa s(-1), respectively).
  
  
  CONCLUSIONS
  Manometry reliably registers non-occluding contractions in the presence of viscous content, and is therefore a viable tool for measuring colonic motility. Interpretation of colonic manometric data, and definitions based on manometric results, must consider the viscosity of luminal content.
authors.affiliation: CSIRO Materials Science and Engineering, Lindfield, NSW, Australia. john.arkwright@csiro.au
authors.forename: J W
authors.initials: JW
authors.lastname: Arkwright
authors.forename: A
authors.initials: A
authors.lastname: Dickson
authors.forename: S A
authors.initials: SA
authors.lastname: Maunder
authors.forename: N G
authors.initials: NG
authors.lastname: Blenman
authors.forename: J
authors.initials: J
authors.lastname: Lim
authors.forename: G
authors.initials: G
authors.lastname: O'Grady
authors.forename: R
authors.initials: R
authors.lastname: Archer
authors.forename: M
authors.initials: M
authors.lastname: Costa
authors.forename: N J
authors.initials: NJ
authors.lastname: Spencer
authors.forename: S
authors.initials: S
authors.lastname: Brookes
authors.forename: A
authors.initials: A
authors.lastname: Pullan
authors.forename: P G
authors.initials: PG
authors.lastname: Dinning
mesh_terms: D000818:Animals; D003106:Colon / Q000502:physiology*; D005260:Female; D005769:Gastrointestinal Motility / Q000502:physiology*; D008365:Manometry / Q000379:methods*; D008954:Models, Biological; D008962:Models, Theoretical; D011817:Rabbits