False Passage Urethra: Causes, Anatomy, and Risks

Injury to the urethra can lead to the formation of a false passage, an unintended channel that complicates urinary function and medical procedures. This condition is often linked to catheterization or trauma, presenting challenges in both diagnosis and management. Recognizing its risks is essential for preventing complications.

Causes Of False Passages

False passages in the urethra are most often caused by improper catheterization, particularly when excessive force is used. The male urethra, with its natural curvatures and narrow sections like the membranous urethra, is especially vulnerable. When resistance is met and force is applied, the catheter can deviate from the normal lumen, creating an artificial tract. This risk increases in patients with benign prostatic hyperplasia (BPH) or urethral stricture disease, where anatomical obstructions make misdirection more likely.

Trauma, both external and medical, is another major cause. Pelvic fractures from high-impact injuries, such as motor vehicle accidents, can disrupt the urethra and lead to false passage formation. Blunt perineal trauma, where the urethra is compressed against the pubic symphysis, can cause partial tears that later develop into false tracts if instrumentation is attempted without proper visualization. Surgical procedures involving the lower urinary tract, including transurethral resections or urethral dilations, also carry a risk, particularly in the presence of pre-existing scarring or fibrosis.

Repeated instrumentation further increases susceptibility. Patients requiring chronic catheterization, such as those with neurogenic bladder dysfunction, face higher risks due to repeated stress on the urethral lining. The use of inappropriate catheter sizes, rigid instruments, or improper self-catheterization techniques exacerbates the issue. Infection or inflammation can weaken the urethral epithelium, making it more prone to injury. Studies indicate that inadequate training in self-catheterization is a frequent cause of false passage formation.

Anatomy Involved

The male urethra’s structure makes it prone to false passage formation due to its length and anatomical variations. Extending from the bladder neck to the external urethral meatus, it consists of anterior and posterior segments. The anterior urethra includes the penile and bulbar portions, while the posterior urethra consists of the membranous and prostatic sections. The membranous urethra is particularly vulnerable due to its narrow diameter and fixed position between the external urethral sphincter and the perineal membrane.

The prostatic urethra, though relatively wide, can be distorted by BPH, increasing the risk of misdirection. The bulbar urethra, located just beyond the membranous section, is another common site for false passages due to its compliant walls. Excessive force during instrumentation can easily perforate this segment.

The urethral epithelium also influences injury susceptibility. The proximal urethra is lined with urothelium, transitioning to pseudostratified columnar epithelium in the mid-urethra and stratified squamous epithelium distally. Thinner epithelial areas, particularly in the membranous and bulbar urethra, are more prone to trauma. The periurethral connective tissue and the sponge-like vascular structure of the corpus spongiosum contribute to extraluminal tract formation when the urethral wall is breached.

Distinguishing Factors In Physical Examination

A thorough physical examination is crucial for identifying a false passage, as clinical signs can be subtle. Patients may report difficulty voiding, hematuria, or discomfort during urination. Examination of the external genitalia can reveal trauma signs such as ecchymosis or swelling, particularly in the perineal region. Tenderness along the penile shaft or perineum may indicate urine extravasation into surrounding tissues.

During catheterization, a key indicator of a false passage is unexpected catheter deviation. Instead of advancing smoothly into the bladder, resistance may be encountered, or the catheter may coil within the urethra without yielding urine. When a prior catheterization attempt has failed at the same location, a false passage is likely.

Palpation of the perineum may reveal abnormal induration, especially in the bulbar urethra. A digital rectal examination in male patients can help identify asymmetry or firm areas along the urethra. In long-standing cases, urinary retention may develop, leading to suprapubic fullness or discomfort.

Imaging Modalities For Confirmation

Imaging techniques are essential for diagnosing a false passage by delineating urethral anatomy and identifying extraluminal tracts. Retrograde urethrography (RUG) is the preferred initial method, using contrast injection under fluoroscopy to reveal irregular contrast extravasation. This technique is particularly useful for detecting false passages in the bulbar and membranous urethra.

Voiding cystourethrography (VCUG) can complement RUG by assessing urinary flow dynamics. This method involves filling the bladder with contrast and capturing images during urination, helping reveal abnormal urine flow patterns. VCUG is useful in cases of recurrent urinary retention or incomplete voiding.

Ultrasound offers a non-invasive alternative, with high-frequency transperineal ultrasound providing real-time visualization of the urethra and surrounding tissues. This technique is particularly beneficial for patients requiring repeated evaluations or when radiation exposure is a concern.

For complex cases, magnetic resonance urethrography (MRU) provides superior soft tissue resolution, making it useful for assessing chronic false passages or extensive fibrosis. Computed tomography (CT) with contrast may be used in trauma-related urethral injuries where concurrent pelvic fractures or deep tissue involvement is suspected.

Potential Complications Of False Passages

Failure to diagnose and manage a false passage can lead to complications affecting urinary function and quality of life. The severity depends on the depth of the false tract, infection presence, and repeated instrumentation. Undiagnosed false passages can widen with repeated catheterization, worsening urinary dysfunction and structural damage.

A major consequence is urethral stricture formation, where healing leads to fibrosis and narrowing of the urethral lumen. Strictures can cause obstructive voiding symptoms, including weak stream, incomplete bladder emptying, and urinary retention. Severe cases can lead to bladder hypertrophy or upper urinary tract damage due to increased intravesical pressure. Surgical intervention, such as urethroplasty, may be required to restore normal function.

Infections are another concern, particularly if urine extravasates into surrounding tissues, fostering bacterial growth. Periurethral abscesses can develop, causing localized pain, swelling, and fever. If untreated, an abscess may rupture into adjacent structures, potentially forming a fistula between the urethra and perineal skin or rectum. Severe infections can progress to urosepsis, a life-threatening condition requiring immediate intervention. Recurrent infections may necessitate prolonged antibiotics, though surgical correction is often needed to prevent recurrence.