title: A novel technique to identify patients with megarectum.
abstract: OBJECTIVE
  Traditional methods of identifying patients with persistent dilation of the rectum, or megarectum, are associated with inherent methodologic limitations. The purpose of this study was to use a barostat to establish criteria for the diagnosis of megarectum and to assess rectal diameter during isobaric (barostat) and volumetric (barium contrast) distention protocols in constipated patients with megarectum on anorectal manometry.
  
  
  METHODS
  During fluoroscopic screening, rectal diameter was measured at minimum distending pressure of the rectum, achieved using a barostat. It was also measured during evacuation proctography (volumetric distention). Having established a normal range in 25 healthy volunteers, 30 constipated patients with evidence of megarectum on anorectal manometry (elevated maximum tolerable volume on latex balloon distention) were studied. A further 10 constipated patients without evidence of megarectum were studied (normal rectum).
  
  
  RESULTS
  Megarectum was diagnosed when the rectal diameter was greater than 6.3 cm at minimum distending pressure. Rectal diameter at minimum distending pressure was increased in 20 patients (67 percent) with megarectum on anorectal manometry, but was normal in the remaining 10 patients (33 percent) and all patients with a normal rectum on anorectal manometry. Rectal diameter was increased at evacuation proctography in only 15 patients (50 percent) with evidence of megarectum on anorectal manometry.
  
  
  CONCLUSIONS
  The prevalence of megarectum is overestimated and underestimated when rectal diameter is assessed using anorectal manometry and contrast studies, respectively. Controlled (pressure-based) distention combined with fluoroscopic imaging allowed accurate identification of patients with megarectum on the basis of a rectal diameter greater than 6.3 cm at the minimum distention pressure. Measurement of rectal diameter at minimum distention pressure may be useful in those patients with an elevated maximum tolerable volume on anorectal manometry when surgery is being contemplated.
authors.affiliation: Gastrointestinal Physiology Unit, Centre for Academic Surgery, Institute of Cell and Molecular Science, Barts and The London, Queen Mary's School of Medicine and Dentistry, Whitechapel, London, United Kingdom. m.a.gladman@qmul.ac.uk
authors.forename: Marc A
authors.initials: MA
authors.lastname: Gladman
authors.forename: Lee S
authors.initials: LS
authors.lastname: Dvorkin
authors.forename: S Mark
authors.initials: SM
authors.lastname: Scott
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Lunniss
authors.forename: Norman S
authors.initials: NS
authors.lastname: Williams
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001466:Barium Sulfate; D016022:Case-Control Studies; D002404:Catheterization; D003248:Constipation / Q000503:physiopathology*; D003287:Contrast Media; D004733:Enema; D005260:Female; D006801:Humans; D008297:Male; D008365:Manometry; D008875:Middle Aged; D012002:Rectal Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D012007:Rectum / Q000503:physiopathology*; D012016:Reference Values
chemical_list: D003287:Contrast Media; D001466:Barium Sulfate