Relation between electromyography and anal manometry of the external anal sphincter

Thirteen patients with faecal incontinence and 26 control subjects were studied to investigate whether a quantitative electromyographic (EMG) signal could be correlated to anal manometry. Three different electrodes were used--a concentric needle electrode, a disposable sponge electrode, and a hard anal plug electrode. The maximum amplitude of the EMG recording was used as a quantitative parameter. Linear regression showed significant correlation between EMG and anal manometry with the sponge electrode, both at rest and during squeeze. Significant correlation was also found with the concentric needle electrode during squeeze but not at rest. No correlation was found with the hard anal plug electrode either during squeeze or at rest. Reproducibility studies using the sponge electrode showed acceptable day to day variation. In conclusion, quantitative EMG recordings from a disposable sponge electrode placed in the anal canal correlate well to anal manometry and may be used for assessment of sphincter function, but the hard anal plug electrode cannot be recommended.