title: Dynamic MR assessment of the anorectal angle and puborectalis muscle in pediatric patients with anismus: technique and feasibility.
abstract: OBJECTIVE
  To assess the feasibility of dynamic breath-hold MRI for evaluating changes in the anorectal angle and movements of the pelvic-floor musculature (puborectalis) during resting and straining states in pediatric patients presenting with anismus.
  
  
  METHODS
  Six pediatric patients (7-13 years old) with chronic constipation and manometric evidence of anismus were assessed by dynamic breath-hold MRI. Changes in the anorectal angle, the degree of pelvic-floor descent, and the thickness and length of the puborectalis muscles were measured during rest and straining. The findings were compared with those obtained in six age- and sex-matched controls.
  
  
  RESULTS
  The children with anismus had a smaller anorectal angle during straining, and the angle decreased from rest to defecation. The puborectalis also became paradoxically shortened and thickened during straining in the anismus group. There were significant differences between the two groups in terms of the change of degree of the anorectal angle, and the thickness and length of the puborectalis muscle during straining.
  
  
  CONCLUSIONS
  Fast dynamic MRI is feasible for evaluating pelvic-floor movement in pediatric patients. Preliminary results suggest that children with anismus have a smaller anorectal angle and a different puborectalis configuration compared to controls.
authors.affiliation: Department of Diagnostic Radiology and Organ Imaging, Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong SAR, China. winnie@med.cuhk.edu.hk
authors.forename: Winnie C W
authors.initials: WC
authors.lastname: Chu
authors.forename: Yuk-him
authors.initials: YH
authors.lastname: Tam
authors.forename: Wynnie W M
authors.initials: WW
authors.lastname: Lam
authors.forename: Alex W H
authors.initials: AW
authors.lastname: Ng
authors.forename: Frances
authors.initials: F
authors.lastname: Sit
authors.forename: Chung-kwong
authors.initials: CK
authors.lastname: Yeung
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D003248:Constipation / Q000503:physiopathology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008365:Manometry; D018482:Muscle, Skeletal / Q000503:physiopathology*; D017773:Pelvic Floor / Q000503:physiopathology*; D018709:Statistics, Nonparametric