Definition and Anatomy

A urethral stricture is an abnormal narrowing of the urethral lumen caused by scar tissue (fibrosis) in the spongy tissue (spongiofibrosis) surrounding the urethra. This scar tissue can be short or long, and its location within the urethra is crucial for diagnosis and treatment planning.

Urethral Anatomy (Male): The male urethra is approximately 18-22 cm long and is divided into several parts:

• Posterior Urethra:

  • Pre-prostatic urethra: Within the bladder neck, before the prostate.

  • Prostatic urethra: Passes through the prostate gland.

  • Membranous urethra: Passes through the external urethral sphincter and perineal membrane. This is the narrowest and least protected part, making it vulnerable to trauma.

• Anterior Urethra:

  • Bulbar urethra: Located in the perineum, surrounded by the bulbospongiosus muscle.

  • Penile (pendulous) urethra: Extends through the penis.

  • Fossa navicularis: The widened portion within the glans penis.

  • Meatus: The external opening of the urethra.

Strictures can occur in any part of the urethra, but certain locations are more common depending on the etiology.

Etiology and Risk Factors

Urethral strictures typically result from scar tissue formation in response to injury, infection, or inflammation. The causes can be categorized as follows:

1. Trauma:

   • Straddle Injuries: Direct trauma to the perineum (e.g., falling onto a bike crossbar, fence), which can crush the bulbar urethra against the pubic bone.

   • Pelvic Fractures: Can cause severe disruption and stricture of the posterior urethra (membranous or prostatic urethra).

   • Iatrogenic Trauma: Injury caused by medical procedures. This is a very common cause.

     • Catheterization: Repeated or traumatic catheterization, prolonged indwelling catheters.

     • Endoscopic Procedures: Transurethral resection of the prostate (TURP), cystoscopy, ureteroscopy.

     • Surgical Procedures: Hypospadias repair, prostatectomy.

2. Infection/Inflammation (Urethritis):

   • Sexually Transmitted Infections (STIs): Historically, gonococcal urethritis (caused by Neisseria gonorrhoeae) was a major cause of strictures, particularly in the bulbar and penile urethra. Other STIs, like Chlamydia trachomatis, can also cause urethritis leading to strictures, though less commonly.

   • Non-STI Urethritis: Less common, but severe or recurrent non-STI urethritis can lead to stricture formation.

   • Lichen Sclerosus (Balanitis Xerotica Obliterans – BXO): A chronic inflammatory skin condition that can affect the glans penis and meatus, leading to progressive scarring and strictures, especially in the fossa navicularis and meatus.

3. Ischemia:

   • Reduced blood supply to the urethral tissue can lead to necrosis and subsequent scarring. This can occur after prolonged pressure (e.g., catheterization) or certain surgical procedures.

4. Congenital:

   • Rarely, strictures can be present from birth (e.g., congenital meatal stenosis, posterior urethral valves).

5. Idiopathic:

   • In a significant number of cases, especially bulbar strictures, no clear cause can be identified. These are termed idiopathic strictures.

Risk Factors:

• History of urethral trauma.

• History of sexually transmitted infections (especially gonorrhea).

• Repeated or difficult urinary catheterization.

• Prior urethral or prostate surgery.

• Lichen sclerosus.

Pathophysiology

The underlying mechanism of urethral stricture formation is the development of spongiofibrosis.

1. Initial Injury/Inflammation: An insult (trauma, infection, ischemia) causes damage to the urethral lining (urothelium) and the underlying corpus spongiosum (the spongy erectile tissue surrounding the urethra).

2. Inflammatory Response: The body mounts an inflammatory response to the injury.

3. Fibroblast Activation: In response to inflammatory mediators and growth factors, fibroblasts within the corpus spongiosum become activated.

4. Collagen Deposition: Activated fibroblasts produce excessive amounts of collagen and other extracellular matrix proteins. This leads to the formation of dense, inelastic scar tissue (fibrosis).

5. Spongiofibrosis: The scar tissue contracts and replaces the normal elastic spongy tissue, causing the urethral lumen to narrow. This scar tissue is often circumferential, causing a tight constriction.

6. Progressive Narrowing: Without intervention, the scar tissue can continue to mature and contract, leading to progressive narrowing of the urethra over time.

7. Impact on Urine Flow: The narrowed lumen increases resistance to urine flow, requiring the bladder to generate higher pressures to empty. This can lead to bladder muscle hypertrophy and dysfunction.

Clinical Manifestations

The symptoms of urethral stricture are primarily related to obstructed urine flow and can develop gradually over time.

• Weak or Decreased Urinary Stream: The most common symptom. Patients may notice a dribbling, spraying, or split stream.

• Hesitancy: Difficulty initiating urination.

• Straining to Urinate: Needing to push or strain to empty the bladder.

• Incomplete Bladder Emptying: Feeling that the bladder is not completely empty after urination.

• Urinary Frequency and Urgency: Due to bladder irritation and incomplete emptying.

• Nocturia: Waking up at night to urinate.

• Post-Void Dribbling: Urine leakage after finishing urination.

• Dysuria: Pain or burning during urination (less common as a primary symptom of stricture itself, but can occur if infection is present).

• Recurrent Urinary Tract Infections (UTIs): Due to urinary stasis behind the stricture.

• Acute Urinary Retention: Complete inability to urinate, a medical emergency.

• Pain: May occur in the perineum or penis, especially during urination or ejaculation.

• Decreased Ejaculatory Force: If the stricture affects the posterior urethra.

Diagnosis

Diagnosing urethral stricture involves a combination of clinical assessment, imaging, and sometimes endoscopic evaluation.

1. Medical History: Detailed inquiry about urinary symptoms, their duration, previous urethral trauma, STIs, and urological procedures.

2. Physical Examination: Examination of the urethral meatus for stenosis or signs of lichen sclerosus. Palpation of the urethra may reveal a thickened or tender area.

3. Urinalysis and Urine Culture: To check for signs of infection (pyuria, bacteriuria) and rule out other causes of dysuria.

4. Uroflowmetry: Measures the maximum flow rate of urine. A reduced peak flow rate (e.g., <10-12 mL/s) suggests obstruction.

5. Post-Void Residual (PVR) Volume: Measures the amount of urine remaining in the bladder after urination. An elevated PVR indicates incomplete bladder emptying due to obstruction.

6. Imaging Studies:

   • Retrograde Urethrogram (RUG): The gold standard for diagnosing anterior urethral strictures. Contrast dye is injected into the urethra from the meatus, and X-rays are taken to visualize the stricture’s location, length, and severity.

   • Voiding Cystourethrogram (VCUG): Used to evaluate the bladder and posterior urethra, especially after pelvic trauma or for suspected posterior strictures. Contrast is instilled into the bladder, and images are taken during urination.

   • Ultrasound Urethrogram: Can be used to assess the length and spongiofibrosis of anterior urethral strictures.

   • Magnetic Resonance Urethrography (MRU): Provides detailed imaging of the entire urethra and surrounding tissues, useful for complex strictures.

7. Cystoscopy: A flexible or rigid scope is inserted into the urethra to directly visualize the stricture. It can confirm the presence of a stricture, assess its location and severity, and identify associated pathology. However, it may not accurately assess the length or density of the stricture.

Management

Management of urethral strictures aims to restore normal urinary flow and prevent complications. Treatment options depend on the stricture’s location, length, severity, and cause, as well as patient factors.

1. Endoscopic Management:

• Urethral Dilation: Gradual stretching of the stricture using dilators. This is a simple, minimally invasive procedure but often provides only temporary relief, and strictures tend to recur.

• Direct Visual Internal Urethrotomy (DVIU): An endoscopic procedure where the stricture is incised (cut) using a cold knife or laser under direct vision. It is more effective than dilation for short, non-dense strictures, particularly in the bulbar urethra, but recurrence rates can still be high (especially for longer or recurrent strictures).

2. Open Surgical Management (Urethroplasty):

• Considered the gold standard for definitive, long-term treatment of urethral strictures, especially for recurrent or longer strictures.

• Involves excising the strictured segment and rejoining the healthy ends (excision and primary anastomosis) or using tissue grafts (e.g., buccal mucosa, skin) to reconstruct the urethra.

• Excision and Primary Anastomosis: For short strictures, the narrowed segment is removed, and the healthy ends of the urethra are sewn together. This has high success rates.

• Substitution Urethroplasty: For longer strictures, a graft (most commonly buccal mucosa from the cheek) or a flap of skin is used to augment or replace the strictured segment of the urethra.

• Urethroplasty is a complex procedure performed by specialized urological surgeons, but it offers the highest long-term success rates.

3. Other Management Options:

• Self-Catheterization: Patients may be taught to intermittently pass a small catheter through the urethra to keep the stricture dilated. This is a palliative measure for patients who are not candidates for or decline surgical repair.

• Urethral Stents: Rarely used, as they can cause complications like encrustation, pain, and migration.

• Permanent Catheterization (Suprapubic or Urethral): For patients with severe, recurrent, or untreatable strictures who cannot undergo reconstructive surgery.

Complications

Urethral strictures, if left untreated or inadequately managed, can lead to significant complications:

• Recurrent Urinary Tract Infections (UTIs): Due to urinary stasis behind the stricture.

• Acute Urinary Retention: Complete inability to urinate, requiring emergency catheterization.

• Bladder Stones: Formation of stones in the bladder due to incomplete emptying and urinary stasis.

• Bladder Dysfunction: Chronic obstruction can lead to thickening of the bladder wall (trabeculation), diverticula (outpouchings), and eventually bladder decompensation and failure.

• Hydronephrosis and Renal Impairment: Back-pressure on the kidneys due to chronic obstruction, leading to kidney damage and potentially renal failure in severe, long-standing cases.

• Epididymitis and Prostatitis: Infection can ascend from the urethra to the epididymis or prostate.

• Urethral Fistula: Abnormal tract forming from the urethra to the skin or other organs.

• Urethral Abscess: Collection of pus around the urethra.

• Malignancy: Long-standing, untreated strictures, particularly those caused by chronic inflammation or prior radiation, may rarely be associated with an increased risk of urethral cancer.