What is the anatomy of the ureter and ureterovesical junction (UVJ)?

Anatomy of the Ureter and Ureterovesical Junction (UVJ)

The ureter is a muscular tube that transports urine from the renal pelvis to the bladder, with its distal portion forming a specialized anti-reflux mechanism at the ureterovesical junction.

Ureteral Anatomy

Anatomical Divisions

• The ureter is anatomically divided by the iliac vessels, which serve as a critical surgical landmark for injury management 1
• Proximal ureter: Located above (cranial to) the iliac vessels 1
• Distal ureter: Located below (caudal to) the iliac vessels, where the blood supply becomes more tenuous 1

Structural Components

• The ureteral wall consists of inner and outer muscular layers that are butyrylcholinesterase-positive and merge into a single longitudinal layer at the UVJ level 2
• These muscle fibers fan out distally to end at the bladder mucosa or intermingle with fibers from the contralateral ureter 3
• The ureter is surrounded by Waldeyer's sheath, a fibromuscular/fibroconjunctive sheath that fixes the juxtavesical ureter to the bladder wall 4, 5

Ureterovesical Junction (UVJ) Anatomy

Location and Course

• The UVJ represents where the ureter enters the bladder wall and travels obliquely through it before opening at the ureteral orifice 4, 5
• The intramural (intravesical) ureter has a very short truly submucosal segment, as the inner detrusor muscle layer extends almost to the ureteral orifice 5
• The ureter tunnels obliquely through the bladder wall, creating a flap-valve mechanism 2

Muscular Architecture

• The terminal ureter demonstrates perfect continuity with the trigone, with abundant fibroelastic connective fibers running longitudinally alongside muscle fibers 5
• Three distinct muscle groups participate in UVJ formation 2:
  1. The detrusor muscle and deep trigone (acetylcholinesterase-positive)
  2. The ureteral muscle layers (butyrylcholinesterase-positive) that form the superficial trigone
  3. The muscularis mucosae (discontinuous, absent from trigone)
• No direct muscular connections exist between the ureter and bladder musculature—they function as separate entities 2, 3

Neuroanatomy

• Nerves occupy the medial aspect of the distal ureter and encircle the entire ureter at the UVJ level 4
• These nerves travel just outside Waldeyer's sheath, creating a safe plane for surgical dissection beneath the sheath 4
• As the ureter tunnels into the bladder, nerves localize to the lateral wall of the detrusor muscle 4
• Both S-100 and nitric oxide synthase (nNOS) positive nerve fibers spread among detrusor fibers in the trigonal area 4

Anti-Reflux Mechanism

Functional Model

• The UVJ functions as a valve to prevent vesicoureteral reflux (VUR) by protecting the low-pressure upper urinary tract from bladder pressure 2
• During ureteric peristalsis, the urine bolus arrives at the UVJ, and the ureter shortens and slides freely in its tunnel to discharge urine into the bladder 2
• Ureteric constriction from peristalsis and thickening of the contracted portion prevents upstream leakage 2
• Distal spreading of peristalsis into the superficial trigone increases the submucosal ureteric length and prevents reflux 2
• The compliance of the intravesical ureter depends on the balance between muscle fibers and fibroelastic connective tissue—disruption of this balance can create functional obstruction 5

Clinical Implications

Surgical Considerations

• Careful dissection within Waldeyer's sheath is recommended during ureteral reconstructive surgery to preserve the nerves and maintain bladder function 4
• The absence of muscular connections between ureter and bladder means the ureter slides freely, which is essential for normal function 2, 3
• Understanding that no classic ureteral sphincter mechanism exists—the anti-reflux mechanism relies on the oblique tunnel, mucosal flap, and coordinated muscle activity 3

Pathophysiology

• Obstruction at the UVJ can occur from hypertrophied bladder wall, as seen in posterior urethral valves where increased bladder pressure affects the junction 6
• Modification of the fibroelastic-to-muscle fiber balance can create functional obstruction even without anatomical blockage 5