Correlation of intraurethral ultrasonography and needle electromyography of the urethra

Objective: To correlate structural intraurethral ultrasound findings with n eedle electromyography of striated urethral sphincters in young continent n ulliparas. Methods: Twenty-three nulliparas, each less than 35 years old and without p elvic floor disorders, were recruited at Methodist Hospital in Indianapolis , Indiana, and the University of Louisville in Louisville, Kentucky. Each h ad concentric needle electromyography of their urethra to localize their sh riated urethral sphincter. Intraurethral ultrasound was used to identify th e needle tip and layer in which it was found, examine the sonographic appea rance of periurethral anatomy, and measure the thickness of hypoechoic and outer hyperechoic layers. Results: Three layers were seen on intraurethral ultrasound: a mildly hyper echoic inner layer, a hypoechoic middle layer, and a hyperechoic outer laye r. The concentric needle tip was seen in all subjects and showed motor unit action potentials when located in the outer hyperechoic layer. The mean th ickness of the hypoechoic layer was 2.5 mm, and the mean thickness of the o uter hyperechoic layer was 2.6 mm. Conclusion: Motor unit action potentials showed that striated muscle was pr esent in the outer hyperechoic layer on intraurethral ultrasound, implying that it contains the striated urethral sphincter. (Obstet Gynecol 2000;95:1 56-9. (C) 2000 by The American College of Obstetricians and Gynecologists.) .