Electromyography of the pelvic floor musculature in the assessment of obstructed defecation symptoms

PURPOSE: The purpose of this study was to use electromyography to examine the behavior of the external sphincter, puborectalis muscle, and pubococcygeus muscle during attempted defecation in patients with symptoms of obstructed defecation and in normal subjects to highlight differences of clinical significance. METHODS: A total of 35 patients (31 females) aged 20 to 80 (mean, 53.7 +/- 13.3) years with unprepared bowel who had normal colon transit time and obstructed defecation symptoms and 12 voluntary control subjects (7 females) aged 23 to 68 (mean, 48 +/- 11.5) years under-went an electromyography evaluation of the activity of the external sphincter, puborectalis muscle, and pubococcygeus muscle during attempted defecation. The patients were also examined in separate sessions with defecography and anal manometry. RESULTS: During attempted defecation, puborectalis muscle and external sphincter always reacted in the same manner. When evaluated with pubococcygeus muscle, three main patterns of activity were observed either in patients or in controls: 1) coordinated activation pattern; 2) coordinated inhibition pattern; and 3) uncoordinated or equivocal pattern: activation of pubococcygeus muscle with inhibition of puborectalis muscle/external sphincter, activation followed by inhibition of the three muscles, and activation followed by inhibition of pubococcygeus muscle and no change in the others. We never observed activation of puborectalis muscle/external sphincter concomitant with inhibition of pubococcygeus muscle. The inhibitory coordinated pattern occurred significantly (P = 0.01) more frequently in controls than in patients. These subjects also presented a significantly (P = 0.01) lower frequency of pubococcygeus muscle inhibition. CONCLUSIONS. Either activation or inhibition appears as a physiological behavior, possibly adopted in different circumstances, of the pelvic floor muscles during attempted defecation. The higher prevalence of coordinated inhibitory patterns in normal subjects and the lower frequency of pubococcygeus muscle inhibition in patients with symptoms of obstructed defecation, however, suggests that a loss of inhibition capacity progressing from pubococcygeus muscle to puborectalis muscle/external sphincter muscles could determine the insurgence of obstructed defecation symptoms in some subjects, who should therefore benefit from biofeedback retraining aimed at reacquisition of the inhibition capacity of all muscles of the pelvic floor during defecation.