Urethral stricture


A urethral stricture is a narrowing of the urethra, the tube connected to the bladder that allows urination. The narrowing reduces the flow of urine and makes it more difficult or even painful to empty the bladder.
Urethral stricture is caused by injury, instrumentation, infection, and certain non-infectious forms of urethritis. The condition is more common in men due to their longer urethra.

Signs and symptoms

The hallmark sign of urethral stricture is a weak urinary stream. Other symptoms include:
Some people with severe urethral strictures are completely unable to urinate. This is referred to as acute urinary retention, and is a medical emergency. Hydronephrosis and kidney failure may also occur.

Complications

Urethral strictures most commonly result from injury, urethral instrumentation, infection, non-infectious inflammatory conditions of the urethra, and after prior hypospadias surgery. Less common causes include congenital urethral strictures and those resulting from malignancy.
Urethral strictures after blunt trauma can generally be divided into two sub-types;
  • Pelvic fracture-associated urethral disruption occurs in as many as 15% of severe pelvic fractures. These injuries are typically managed with suprapubic tube placement and delayed urethroplasty 3 months later. Early endoscopic realignment may be used in select cases instead of a suprapubic tube, but these patients should be monitored closely as vast majority of them will require urethroplasty.
  • Blunt trauma to the perineum compresses the bulbar urethra against the pubic symphysis, causing a "crush" injury. These patients are typically treated with suprapubic tube and delayed urethroplasty.
Other specific causes of urethral stricture include:
  • Instrumentation
  • Infection
  • Lichen sclerosus
  • Surgery to address hypospadias can result in a delayed urethral stricture, even decades after the original surgery.

    Diagnosis

Among ways to diagnose this condition is:
Initial treatment usually involves urethral dilation or urethrotomy, where the stricture is cut away with a cystoscope.

Dilation and urethrotomy

Urethral dilation and other endoscopic approaches such as direct vision internal urethrotomy, laser urethrotomy, and self intermittent dilation are the most commonly used treatments for urethral stricture. However, these approaches are associated with low success rates and may worsen the stricture, making future attempts to surgically repair the urethra more difficult.
A Cochrane review found that performing intermittent self-dilatation may confer a reduced risk of recurrent urethral stricture after endoscopic treatment, but the evidence is weak.

Urethroplasty

refers to any open reconstruction of the urethra. Success rates range from 85% to 95% and depend on a variety of clinical factors, such as stricture as the cause, length, location, and caliber. Urethroplasty can be performed safely on men of all ages.
In the posterior urethra, anastomotic urethroplasty is typically performed after removing scar tissue.
In the bulbar urethra, the most common types of urethroplasty are anastomotic and substitution with buccal mucosa graft, full-thickness skin graft, or split thickness skin graft. These are nearly always done in a single setting.
In the penile urethra, anastomotic urethroplasties are rare because they can lead to chordee. Instead, most penile urethroplasties are substitution procedures utilizing buccal mucosa graft, full-thickness skin graft, or split-thickness skin graft. These can be done in one or more settings, depending on stricture location, severity, cause and patient or surgeon preference.

Urethral stent

A permanent urethral stent was approved for use in men with bulbar urethral strictures in 1996, but was recently removed from the market.
A temporary thermoexpandable urethral stent is available in Europe but is not currently approved for use in the United States.

Emergency treatment

When in acute urinary retention, treatment of the urethral stricture or diversion is an emergency. Options include:
  • Urethral dilatation and catheter placement. This can be performed in the Emergency Department, a practitioner's office or an operating room. The advantage of this approach is that the urethra may remain patent for a period of time after the dilation, though long-term success rates are low.
  • Insertion of a suprapubic catheter with catheter drainage system. This procedure is performed in an Operating Room, Emergency Department or practitioner's office. The advantage of this approach is that it does not disrupt the scar and interfere with future definitive surgery.

    Ongoing care

Following urethroplasty, patients should be monitored for a minimum of 1 year, since the vast majority of recurrences occur within 1 year.
Because of the high rate of recurrence following dilation and other endoscopic approaches, the provider must maintain a high index of suspicion for recurrence when the patient presents with obstructive voiding symptoms or urinary tract infection.

Research

Urethrotomy vs. urethroplasty

Comparing the two surgical procedures, a UK trial found that both urethrotomy and urethroplasty are effective in treating urethral narrowing in the bulbar region. At the same time the more invasive urethroplasty had longer-lasting benefit and was associated with fewer re-interventions. The results were integrated into the new UK guidelines on the treatment urethral narrowing by British Association of Urological Surgeons.

Bioengineering

The use of bioengineered urethral tissue is promising, but still in the early stages. The Wake Forest Institute of Regenerative Medicine has pioneered the first bioengineered human urethra and in 2006 implanted urethral tissue grown on bioabsorbable scaffolding in five young males who had congenital defects, physical trauma, or an unspecified disorder necessitating urethral reconstruction. As of March 2011, all five recipients report the transplants have functioned well.

Cell therapy approach through endoscopy

Buccal mucosal tissue harvested under local anesthesia after culturing in the lab when applied as cells through endoscopy after urethrotomy in a pilot study has yielded encouraging results. This procedure has subsequently been standardised for in vitro cell culture, then in animal models of urethral stricture for both morphological engraftment of the buccal cells onto the site of the urethral injury and also immunohistochemically by negative and positive markers confirming that the transplanted cells are the ones that got engrafted covering the wounded surface of the urethra, leading to possible prevention of recurrence of the stricture. A hybrid combination of cells cultured in 2D yielding paracrine effect through IGF-1 secretion and those cultured in 3D Festigel polymer engrafting on to the urethrotomy site together are considered as mechanism of the patency. Clinically, this procedure has been started as an application in Japan as per the regenerative medicine law of Japan. Based on earlier reports of finely hashed tissue bits of buccal tissue transplanted in urethral stricture models having shown engraftment at the site of urethrotomy, a simplified version of this cell therapy approach named BHES-HAUS as a clinical trial, using an excess endotoxin-free thermo-responsive gel scaffold carrier for cell transplant is underway. with preliminary results in post-BMG plasty failure reported.