PARADOXICAL SPHINCTER REACTION IS INFLUENCED BY RECTAL FILLING VOLUME

PURPOSE: Paradoxical sphincter reaction is frequently found in constip ated patients but sometimes also in incontinent patients and in asympt omatic subjects. Its significance in defecation disorders has, therefo re, been debated. The aim of the present study was to investigate whet her paradoxical sphincter reaction is influenced by rectal filling vol ume. PATIENTS AND METHODS: Eighteen patients with defecation disorders and paradoxical sphincter reaction shown by electromyography were rei nvestigated with an extended electromyographic investigation while in the lying position and while in the sitting position, with 50-ml, 100- ml, and 150-ml water-filled rectal balloons. RESULTS: All 18 patients showing paradoxical sphincter reaction in the first investigation also showed the reaction at the second investigation in the lying position with a 0-ml volume of rectal contents. In the sitting position, with a volume of 150 mi of rectal contents, the increase in electromyograph ic activity disappeared in seven patients (39 percent) and no longer s howed paradoxical sphincter reaction. Electromyography showed decrease d activity in one patient and unchanged activity in six patients durin g straining. A closing reflex was seen after completed straining in al l of these seven patients. CONCLUSIONS: The present study demonstrates that paradoxical sphincter reaction diagnosed by electromyography is influenced by the rectal filling volume and might diminish when the re ctum is filled with contents. The conventional electrophysiologic tech nique in the diagnosis of paradoxical sphincter reaction might, theref ore, overdiagnose this condition.