SONOGRAPHIC, MANOMETRIC, AND MYOGRAPHIC EVALUATION OF THE ANAL SPHINCTERS MORPHOLOGY AND FUNCTION

PURPOSE: A direct comparison of anal sphincter physiology (muscle perf ormance and anatomy-muscle thickness) has not yet been undertaken but may be of importance in patients with defecation disorders. METHODS: W e evaluated 15 healthy volunteers by means of anorectal manometry to d etermine pressure functions of the internal and external anal sphincte r. Transcutaneous electromyography was recorded to assess the electric al activity of the external anal sphincter. Thickness of the anal sphi ncter muscles was measured sonographically from within the anal canal with dorsal projection using a 7.5-MHz 360-degrees rectal panorama sca nner. RESULTS: It was shown that neither is the muscle thickness of th e external anal sphincter during rest (6.26 +/- 1.02 mm) or during squ eezing (7.40 +/- 1.39 mm) correlated to its squeeze pressure (138.8 +/ - 15.2 mmHg), nor is the diameter of the internal anal sphincter (2.09 +/- 0.58 mm) correlated to its resting pressure (61.1 +/- 15.2 mmHg). Finally, the thicker the internal anal sphincter muscle, the lower th e electrical activity of the external anal sphincter during squeezing (r = 0.74, P < 0.001). CONCLUSION: It is concluded that both manometry to assess sphincter function and sonography to determine sphincter mo rphology are important measures in the evaluation of continence functi on.