Revisiting the external urethral sphincter: new anatomical insights from a human cadaver study

The external urethral sphincter (EUS) is critical for urinary continence, but its complex anatomy is not fully understood, complicating its preservation during prostate surgeries. This study aims to elucidate the anatomy and development of the EUS to enhance surgical techniques for continence preservation.

The study consisted of a postmortem examination of three male cadavers, aged 52, 64, and 60, with intact urogenital systems. Specimens including the prostate and EUS were dissected, fixed in formalin, and stained with Hematoxylin-Eosin for microscopic analysis. Histological assessments focused on the muscle composition and structure of the EUS and prostate.

Macroscopic examination revealed symmetrical prostates without pathologies. Histologically, the anterior prostate lacked tubuloalveolar glands, showing striated muscle fibers from the external urethral sphincter extending into the prostate and prostatic urethra. Reduced glandular structure and prevalent smooth muscle were noted. This intricate integration of striated muscle fibers at the EUS-prostate interface underscores the anatomical complexity vital for surgical preservation of urinary continence.

Our study reveals a complex EUS-prostate relationship, challenging the view of the EUS as merely a circular muscle. The findings demonstrate the importance of the EUS's extension into the prostate for urethral stabilization and continence. Recognizing this anatomy is crucial for maintaining urinary continence in prostate surgeries and enhancing postoperative outcomes.