Functional anatomy of the human ureterovesical junction

Area of Science:

• Urology
• Anatomy
• Physiology

Background:

• The ureterovesical junction (UVJ) plays a critical role in preventing urine reflux from the bladder to the upper urinary tract.
• Despite its importance, the precise microanatomy of the human UVJ remains a subject of debate.

Purpose of the Study:

• To investigate the detailed microanatomy of the human ureterovesical junction.
• To elucidate the muscular architecture and its role in UVJ function and preventing vesicoureteral reflux.

Main Methods:

• Study of ten fresh cadaveric bladders (3 male, 7 female, mean age 70).
• Bladders were fixed, frozen, and serially sectioned within 24 hours postmortem.
• Cholinesterase activity (acetyl- and butyryl-) was visualized to map muscle distribution, enabling 3D reconstruction of UVJ musculature.

Main Results:

• Identified three distinct muscle groups: acetylcholinesterase-positive detrusor/deep trigone; butyrylcholinesterase-positive ureteric muscle forming the superficial trigone; and a discontinuous muscularis mucosae.
• The inner and outer ureteric muscle layers merge into a single longitudinal layer at the UVJ.
• No direct muscular connection was observed between the ureter and bladder musculature.

Conclusions:

• The UVJ anatomy supports a model where ureteric peristalsis involves shortening and sliding within its tunnel to expel urine.
• Ureteric constriction and thickening prevent upstream leakage, while distal spreading in the superficial trigone enhances submucosal length, preventing reflux.
• This detailed anatomical understanding provides insight into the functional mechanisms of the ureterovesical junction.