Amplitude and recovery velocity of relaxation induced by rectoanal inhibitory reflex and its importance for obstructive evacuation.

Background: The rectoanal inhibitory reflex has an important rule in the fecal continence mechanism. Alterations in this reflex can be associated with compromised anal sphincteric function.

Aim: To identify possible correlation between rectoanal inhibitory reflex parameters and intestinal constipation due to obstructive evacuation.

Patients: Sixty nine patients with intestinal constipation had been submitted to anorectal manometry. It was selected 29 patients (27 female, mean age of 42.3 (19-73) years) having intestinal constipation owing to obstructive evacuation. Thirteen individuals without anorectal functional complaints (eight female, mean age 52.5 (28-73) years) formed the control group.

Results: The mean value of resting anal pressure before rectoanal inhibitory reflex in the proximal and distal anal canals were 61.8 mm Hg and 81.7 mm Hg respectively, for the constipated patients, and 46.0 mm Hg and 64.5 mm Hg, respectively, for asymptomatic individuals. The mean pressure at the point of maximal relaxation in constipated patients was 29.0 mm Hg in the proximal anal canal, and 52.1 mm Hg in the distal anal canal, whilst in the asymptomatic group they were 17.8 mm Hg and 36.3 mm Hg, respectively. The mean percentage difference between the mean resting anal pressure and the mean point of maximal relaxation pressure in the proximal anal canal (amplitude of relaxation) was 54.1% in constipated patients and 54.3% in asymptomatic individuals. In the distal anal canal it was, respectively, 35.6% in constipated patients, and 38.5% in the control group. The average recovery velocity of relaxation in the proximal anal canal was 4.06 mm/second in constipated patients and 2.98 mm/second in asymptomatic individuals, giving a significant difference between the two groups, as well as in the distal anal canal (3.9 mm/second and 2.98 mm/second, respectively)

Conclusion: The greater recovery velocity of the resting anal pressure in the proximal anal canal in constipated patients than in controls may be associated with obstructive evacuation.