Flow evaluation and simultaneous external sphincter electromyography in clinical urodynamics.

More than 200 patients have undergone combined uroflowmetry and external sphincter electromyography studies in our urodynamic laboratories. Pediatric surface electrocardiographic electrodes placed on the perianal skin were used to monitor skeletal muscle electromyographic activity while the patient voided into a standard load-cell type of uroflowmeter. The findings indicate clearly that 1) flow electromyography is reliable and easy to perform, 2) striated muscle electromyographic activity is reduced during normal voiding, 3) external sphincter dyssynergia is rare in patients without true neurologic disease and 4) many patients, especially women, void by straining, which causes an increase in external sphincter electromyographic activity but, generally, does not impair voiding. Results of this study suggest that sphincter dyssynergia has been overdiagnosed. With the use of the flow electromyography study the behavior of the external striated muscle sphincter during voiding can be demonstrated easily and reliably in most clinical urodynamic evaluations.