Ureterovesical Junction

1. Overview

The ureterovesical junction (UVJ) is the anatomical site where the ureter meets the urinary bladder. It acts as a critical one-way valve that allows urine to flow from the ureter into the bladder while preventing backflow. The UVJ is vital for maintaining unidirectional urine flow, protecting the upper urinary tract from vesicoureteral reflux and high bladder pressures.

2. Location

The UVJ is located at the posterolateral aspect of the urinary bladder base, specifically:

• Just inside the bladder wall at the superolateral corners of the trigone.

• Positioned where the distal intramural ureter penetrates the bladder wall obliquely.

This positioning is key to its anti-reflux function, especially during bladder filling and voiding.

3. Structure

The UVJ comprises several structural components:

• Intramural ureter: The terminal 1–2 cm segment of the ureter that tunnels obliquely through the bladder wall.

• Transitional epithelium (urothelium): Lines both the ureter and bladder, allowing distension and preventing urine leakage.

• Submucosal tunnel: Formed by the ureter as it courses through the detrusor muscle and bladder mucosa.

• Flap-valve mechanism: As the bladder fills, pressure compresses the intramural ureter against the bladder wall, closing the UVJ and preventing reflux.

4. Function

The UVJ has several important functions:

• Allows urine entry: Facilitates intermittent boluses of urine from the ureter into the bladder.

• Prevents reflux: Acts as a one-way valve to stop urine from flowing backward into the ureters and kidneys.

• Pressure regulation: Buffers the ureters and kidneys from sudden increases in intravesical pressure during micturition.

5. Physiological Role(s)

The ureterovesical junction plays key physiological roles in the urinary system:

• Anti-reflux control: Prevents vesicoureteral reflux (VUR), which can lead to renal scarring and infections.

• Urinary coordination: Synchronizes ureteral peristalsis with bladder filling and voiding cycles.

• Sensory modulation: UVJ contains sensory receptors that contribute to reflex control of bladder function.

6. Clinical Significance

Vesicoureteral Reflux (VUR)

Occurs when the UVJ fails to prevent backward flow of urine into the ureter and kidneys. Causes include:

• Congenital UVJ incompetence (primary VUR)

• Increased bladder pressure or obstruction (secondary VUR)

Symptoms: recurrent urinary tract infections (UTIs), hydronephrosis, and renal scarring. Diagnosed with voiding cystourethrogram (VCUG). Treatment may involve:

• Prophylactic antibiotics (mild cases)

• Endoscopic injection of bulking agents

• Surgical ureteral reimplantation

Ureteral Obstruction

Narrowing or scarring of the UVJ may block urine flow from the ureter to the bladder, leading to:

• Hydronephrosis

• Flank pain

• Infections

Treatment includes balloon dilation, ureteral stenting, or surgical reconstruction.

Ureterocele

A cystic dilation of the distal ureter protruding into or through the UVJ into the bladder lumen. It can cause obstruction, VUR, or infection. Managed by endoscopic incision or excision and reimplantation.

Congenital Anomalies

Malformed or ectopic UVJs are common in pediatric urology. Examples include:

• Ectopic ureter: Opens below the sphincter in females, causing continuous incontinence.

• Duplicated ureters: May result in separate UVJs with different drainage patterns.

UVJ Calculi

The UVJ is one of the three natural constriction points of the ureter, making it a common site for stone impaction. Symptoms include:

• Severe colicky flank pain

• Hematuria

• Urinary urgency or frequency

Diagnosed with non-contrast CT or ultrasound; treatment may include ureteroscopy or lithotripsy.

Endoscopic and Surgical Importance

During cystoscopy, the UVJs are identified and evaluated for urine jet flow. They are also critical landmarks in:

• Stent placement

• Retrograde pyelography

• Ureteral reimplantation surgeries