Assessment of the anal sphincter muscle: Comparison of a digital and a manometric technique

ObjectivesTo determine if there is a relationship between digital anal use of the modified Oxford Scale for assessment of anal sphincter muscle strength and anal manometric assessment.DesignA prospective, correlational, within-subject design, using two different techniques, in random order, at the same session.SettingThe physiotherapy outpatient department of a district general hospital.ParticipantsSeventy subjects (57 females) with a mean age of 56.3 years. All were attending for physiotherapy treatment of pelvic floor dysfunction.InterventionsSubjects carried out three consecutive pelvic floor muscle contractions each, for digital assessment and for manometric assessment.Main outcome measuresThe relationship between the median of the three digital and the mean of the three manometric measurements was examined using the Spearman rank correlation coefficient.ResultsThere was a low, positive correlation between the median of the digital scores and the mean of the manometric pressures (rs = 0.33, P < 0.005).ConclusionsThis study poses questions about the use of the modified Oxford Scale for assessment of the anal sphincter muscle. Issues include the subject's body mass index and the probe design. The quality of anal resting tone, though crucial to its function, is not addressed by the modified Oxford Scale. Further work is needed to develop a robust method of anal sphincter assessment.