Electromyographic findings of paradoxical puborectalis contraction correlate poorly with cinedefecography

Abstract.

Background:

Both intra-anal sponge electromyography (SEMG) and needle electromyography (NEMG) are used to diagnose paradoxical puborectalis contraction (PPC). The aim of this retrospective study was to assess the correlation among SEMG and NEMG and cinedefecography (CD) in the diagnosis of PPC.

Methods:

Between 1992 and 1999, a total of 261 constipated patients underwent both CD and EMG: 64 had NEMG while 197 had SEMG. PPC was diagnosed by EMG when there was failure to achieve a significant decrease in electrical activity of the puborectalis muscle during attempted evacuation. CD criteria for PPC included lack of straightening of the anorectal angle or persistence of the puborectalis impression during evacuation. CD was considered diagnostic and EMG results were thus compared with those of CD. Agreement was calculated using the kappa statistics (κ) for concordance.

Results:

Both NEMG and SEMG had low positive predictive rates (33% in NEMG, 28% in SEMG) and high negative predictive rates (91% in NEMG, and 78% in SEMG) when correlated with CD findings. Agreement between NEMG and CD was noted in 46 of 64 patients (72%, κ=0.274) while there was agreement between SEMG and CD in 120 of 197 patients (61%; κ=0.067); p>0.05 needle vs. sponge.

Conclusion:

Although both NEMG and SEMG have a low positive predictive values, they have high negative predictive value for PPC. Therefore, neither NEMG nor SEMG alone are optimal tests for diagnosing the presence of PPC.