Electromyographic Lag Time and Opening Time: Two Novel Noninvasive Methods to Investigate Patients with Anal Outlet Obstruction and Their Response to Treatment

Abstract

Methods in use can diagnose anal outlet obstruction but not degree of obstruction. We introduced two novel noninvasive methods of diagnosing and evaluating the degree of anal outlet obstruction: pelvic floor electromyographic lag time and opening time. Pelvic floor electromyographic lag time measured time interval between start of pelvic floor muscle relaxation and start of anal outlet flow. Opening time calculated time lapse between start of rectal contraction and start of anal outlet flow. We investigated the hypothesis that pelvic floor electromyographic lag time and opening time can be used as investigative tools in diagnosing and evaluating degree of anal outlet obstruction. Thirty-one patients with anal outlet obstruction and 26 healthy volunteers were studied. Electromyography of external anal sphincter and anal and rectal pressures were recorded on rectal balloon distension until balloon was expelled. Pelvic floor electromyographic lag time and opening time were measured. Mean opening time and pelvic floor electromyographic lag time of the anal outlet obstruction patients showed significant increase compared to those of healthy volunteers. Pelvic floor electromyographic lag time was longer than opening time in both patients and controls, but the difference was not significant. Biofeedback effected improvement in 24 of the 31 patients. Thus, two novel investigative tools—opening time and pelvic floor electromyographic lag time—in diagnosis of anal outlet obstruction are presented. They exhibited significant increase in anal outlet obstruction patients over the healthy volunteers. There was no significant difference between pelvic floor electromyographic lag time and opening time readings.

KEYWORDS:

• biofeedback
• constipation
• electromyography
• external anal sphincter
• pelvic floor muscles