Megacolon is the result of an extensive lesion of the mioenteric plexus, with lack of motor coordination and achalasia of the anal sphincter. The motility disorder caused by the muscle contraction problems added to a mechanical obstacle results cause constipation. The defecation rectal pressure increases and reaches its peak with the start of fecal flow, exceeding the anal pressure. The objective of this work was to assess the ratio of rectal / anal pressure on 29 megacolon sufferers, compared to normal subjects. Results have shown that defecation rectal pressure was higher than expected for both men (72,2 ± 29,1 cm water) and women (64,5 ± 20,1 cm water) exceeding the defecation anal pressure (66,4 ± 23,2 and 62,1 ± 28,7 cm water, for men and women, respectively). The defecation pressures were much higher than those of the control group, what led to the conclusion that as an adaptive reaction, muscular effort increases to make evacuation possible.
megacolon; manometry; achalasia; defecation; anal sphincter
