Morphological Evaluation of the Male External Urethral Sphincter Complex by Transrectal Ultrasound: Feasibility Study and Potential Clinical Applications

Introduction: Previous measurement of the male external urethral sphincter complex (EUSC) length by magnetic resonance imaging and urethral pressure profilometry did not consider the intraprostatic portion, although its role for urinary continence has been demonstrated. The aim of our study was to verify the feasibility of a morphological evaluation of the EUSC by transrectal ultrasound (TRUS). Materials and Methods: Data from 52 men that underwent TRUS were prospectively collected. The EUSC was identified in the midline sagittal plane. Total and intraprostatic EUSC length and prostate volume were measured. Results: EUSC appears as a hypoechoic area surrounding the urethra. The proximal end was identified between the verumontanum and the prostate apex by the net change in prostate echo patterns, while the distal end was identified by voluntary contraction of the external anal sphincter. Mean total and intraprostatic EUSC lengths were 20.17 and 3.78 mm, respectively. Total EUSC length presented a weak correlation with prostate volume (r = 0.41; p = 0.003), while the intraprostatic portion had a stronger correlation (r = 0.60; p = 0.001). Conclusions: The evaluation of the EUSC is feasible by TRUS, and length measurement should include the intraprostatic portion. Potential clinical application should be the preoperative assessment of the risk of urinary incontinence in men undergoing radical prostatectomy.