Comparative study between intra-anal sponge and needle electrode for electromyographic evaluation of constipated patients

The aim of this study was to compare the intra-anal sponge electrode with the conventional needle electrode for electromyography of the pelvic floor in constipated patients. Forty consecutive patients (27 females) with a mean age of 64.3 (range, 15-87) years who had chronic constipation were prospectively evaluated for electromyographic evidence of nonrelaxation or paradoxical contraction of the puborectalis and external anal sphincter during simulated defecation. The soft intra-anal sponge electrode and then the concentric needle electrode were used in each patient as an internal control. Furthermore, in all patients, cinedefecography was used as an independent standard to confirm the diagnosis. Agreement was calculated using the kappa statistic. Confirmation of needle electromyography was noted in 19 of 20 patients (95 percent) who had sponge electromyographic evidence of paradoxical activity. Similarly, concurrence was noted in 19 of 20 patients (95 percent) with normal relaxation of the puborectalis observed with the sponge electrode. Agreement between needle and sponge electromyography was very good (kappa = 0.9), between needle electromyography and cinedefecography was fair (kappa = 0.4), and between sponge electromyography and cinedefecography was moderate (kappa = 0.5). Furthermore, needle electromyography was more painful in all patients compared with sponge electromyography. The soft sponge surface intra-anal electrode is an excellent alternative to the needle electrode for assessment of puborectalis activity in constipated patients. Sponge electromyography has the advantage of being as accurate as, but less painful than, needle electromyography.