[Evaluation of the involvement of the internal anal sphincter by the measurement of the amplitude and duration of the ano-rectal inhibitory reflex]. / Evaluación del compromiso del esfinter anal interno mediante la medición de la intensidad y duración del reflejo ano-rectal inhibitorio.

The aim of this study was the evaluation of a possible correlation between the resting tone of the anal canal (RT) and amplitude and duration of the recto anal inhibitory reflex (RAIR). 94 subjects, 72 women and 22 men, aged 9-91 years (mean 53 years) were studied. Manometric testing was performed on all subjects with a three balloon system. The maximal anal canal resting tone, the amplitude and duration of the RAIR, were measured. According with the RT, subjects were divided on three groups: GROUP I: RT up to 79 mmHg GROUP II: 80 to 120 mmHg and GROUP III: with RT more than 121 mmHg. The amplitude of RAIR was for GROUP I: mean = 7.09 SD:4.93, GROUP II: mean-10.5 SD:7.3, GROUP III: mean 15.14 DS: 8.19. p less than 0.001 between GROUPS I and III. The duration (d/s) of RAIR was for GROUP I: mean = 180 DS:70, GROUP II: 175.6 DS: 68, GROUP III mean: 201.6 DS 86.4. No differences were found between GROUPS I and II (p less than 0.13), I and III (p less than 0.17), and II and III (p less than 0,33). Positive Sperman correlation (p less than 0,001) was found between RT and amplitude of RAIR. The observation of a positive correlation between RT and RAIR amplitude suggest that the functional integrity of the internal sphincter could be also evaluated by the amplitude but not duration of the RAIR.