title: Adaptation of the rectal wall to distension in children with constipation.
abstract: OBJECTIVE
  To determine whether there is significant change in the tension-length relationship of the digestive smooth-muscle mechanical function in constipation in children and to examine a new method of analysis of the mechanical properties of the rectal wall.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  Thirty children with constipation and 30 control children who did not have constipation.
  
  
  METHODS
  Rapid distension of the rectal wall by inflation of a rectal balloon with air.
  
  
  METHODS
  The in vivo rectal pressure-volume P[t,V] curve was determined according to the quasilinear viscoelasticity law. The recorded pressure was defined as the product of 2 functions: the elastic response P0[V] and the reduced relaxation function G[t], a normalized function of time such that P[t,V] = P0[V] x G[t]. Analysis of variance with repeated measures and modelling (linear for P0[V] and exponential plus constant term for G[t] were used for data analysis.
  
  
  RESULTS
  The quasilinear viscoelastic law can be applied to the in vivo determination of the mechanical properties of the rectal wall in controls and in children with constipation. The elastic response was similar in the 2 groups. The reduced relaxation function was significantly different between the 2 groups, with the absence of an asymptotic value in the group with constipation (p < 0.01).
  
  
  CONCLUSIONS
  Distension of the rectal wall with the use of an air-inflated balloon, with this type of interpretation according to the viscoelastic law, is useful in the analysis of chronic constipation.
authors.affiliation: Laboratoire de physiologie digestive, Hôpital Laënnec, Paris, France.
authors.forename: M
authors.initials: M
authors.lastname: Bouchoucha
authors.forename: J P
authors.initials: JP
authors.lastname: Jais
authors.forename: P
authors.initials: P
authors.lastname: Arhan
authors.forename: P
authors.initials: P
authors.lastname: Landais
authors.forename: D
authors.initials: D
authors.lastname: Pellerin
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003248:Constipation / Q000503:physiopathology*; D004548:Elasticity; D006801:Humans; D007223:Infant; D009119:Muscle Contraction / Q000502:physiology; D009126:Muscle Relaxation / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology / Q000503:physiopathology*; D012007:Rectum / Q000502:physiology / Q000503:physiopathology*