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

Abstract

Objectives To 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. Design A prospective, correlational, within-subject design, using two different techniques, in random order, at the same session. Setting The physiotherapy outpatient department of a district general hospital. Participants Seventy subjects (57 females) with a mean age of 56.3 years. All were attending for physiotherapy treatment of pelvic floor dysfunction. Interventions Subjects carried out three consecutive pelvic floor muscle contractions each, for digital assessment and for manometric assessment. Main outcome measures The relationship between the median of the three digital and the mean of the three manometric measurements was examined using the Spearman rank correlation coefficient. Results There was a low, positive correlation between the median of the digital scores and the mean of the manometric pressures ( r s = 0.33, P < 0.005). Conclusions This 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.