What are the causes of urinary obstruction in young males?

Causes of Urinary Obstruction in Young Males

In young males, urethral stricture should be considered as a primary cause of urinary obstruction, along with primary bladder neck dysfunction, posterior urethral valves, and other functional or anatomical abnormalities. 1

Urethral Stricture

Urethral stricture is defined as any abnormal narrowing of the anterior and posterior urethra, which can significantly impact urinary flow and bladder function.

• The most common etiologies of urethral stricture in developed countries are idiopathic (unknown cause), followed by iatrogenic causes (medical procedure-related) 1
• Iatrogenic causes include complications from endoscopic procedures, transurethral resections, and late failure of hypospadias surgery 1
• In developing countries, trauma is the most common cause, reflecting higher rates of road traffic injuries 1
• Common presenting symptoms include decreased urinary stream, incomplete bladder emptying, urinary tract infections, epididymitis, rising post-void residual urine volume, and decreased force of ejaculation 1
• Rare but serious sequelae of untreated stricture may include bladder calculi, urethral abscess, urethral carcinoma, and chronic kidney injury from obstructive uropathy 1

Primary Bladder Neck Obstruction (PBNO)

PBNO is a significant cause of urinary obstruction in young and middle-aged men that is often misdiagnosed.

• Approximately 10% of young/middle-aged men presenting with lower urinary tract symptoms may be affected by PBNO 2
• PBNO patients are typically younger, have lower BMI, fewer comorbidities, lower PSA values, but worse IPSS (International Prostate Symptom Score) scores and lower prostate volumes compared to patients with other causes of LUTS 2
• PBNO is often misdiagnosed as prostatitis, neurogenic bladder, or psychogenic voiding disorder 3
• Diagnosis requires simultaneous measurement of detrusor pressure and uroflowmetry, as simple urodynamic studies cannot distinguish poor flow due to bladder neck obstruction from that caused by poor detrusor contractility 3

Posterior Urethral Valves (PUV)

PUV is the most common cause of neonatal bladder outlet obstruction that may persist into childhood and adolescence.

• PUV occurs in 0.2% to 1% of cases of mild antenatal hydronephrosis but is more frequent (up to 6%) in settings of more severe antenatal hydronephrosis 1
• In male patients with moderate or severe hydronephrosis, voiding cystourethrography (VCUG) plays a crucial role in evaluating urologic abnormalities that may need immediate care 1
• Symptoms include bladder wall thickening and dilated posterior urethra on ultrasound imaging 1

Other Causes

• Benign prostatic obstruction - though less common in young males, it can occur and cause obstructive symptoms 4
• Urethral polyps, meatal stenosis, Cowper duct cyst, and abnormalities of the fossa navicularis 1
• Functional causes such as dysfunctional voiding 1

Diagnostic Approach

A systematic diagnostic approach is essential for identifying the cause of urinary obstruction in young males:

• Urodynamic studies are particularly valuable in young men with LUTS, as clinical diagnosis and treatment are often empiric and inaccurate 4
• Following urodynamic studies, diagnosis may need to be updated in up to 80% of cases, with concomitant change in management required in 68% 4
• Urethro-cystoscopy, retrograde urethrography (RUG), voiding cystourethrography (VCUG), or ultrasound urethrography should be used to make a definitive diagnosis of urethral stricture 1
• Videourodynamic evaluation is the only diagnostic tool that can document pressure/flow parameters and localize functional bladder-neck obstruction 1

Clinical Pearls and Pitfalls

• Young men do not commonly present with voiding urinary symptoms; therefore, urethral stricture should be considered in the differential diagnosis 1
• Misdiagnosis is common - PBNO is frequently misdiagnosed as prostatitis, neurogenic bladder, or psychogenic voiding disorder 3
• Younger patients with more severe LUTS systematically deserve an extensive assessment to rule out PBNO, including urethrocystoscopy and urodynamics with voiding-cysto-urethrogram 2
• Untreated urethral strictures can lead to serious complications including impaired renal function 5
• For recurrent and complex strictures, only open urethral surgery can reliably and permanently remove the infravesical obstruction 5