Urethral stent (Urolom)
Urethral strictures arise from various causes, and a patient can be asymptomatic or present with severe discomfort secondary to urinary retention. Establishing effective drainage of the urinary bladder can be challenging, and a thorough understanding of urethral anatomy and urologic technology is essential. A urologic consultation
should be obtained for any patient presenting to the emergency department with urinary retention secondary to urethral stricture disease.
In general, a urethral stricture is a circumferential band of fibrous scar tissue which
progressively contracts and narrows the urethral lumen. Strictures of this type may be congenital or may result from urethral trauma or disease. Strictures were traditionally treated by dilation with sounds or bougies. More recently, balloon catheters became available for dilation.
Surgical urethrotomy is currently the preferred treatment, but restenosis remains a significant problem.
Recent advances in biomedical engineering have led to the development of stenting i.e., mechanical scaffolding, to prevent restenosis and keep the previously occluded lumens open.
There are two general types of stents: permanent and temporary. Temporary stents can be further subdivided into removable and absorbable. Permanent stents are used where long term structural support or restenosis prevention is required, or in cases where surgical removal of the implanted stent is impractical. Permanent stents are usually made from metals such as Phynox, 316 stainless steel, MP35N alloy, and superelastic Nitinol (nickel-titanium).
Permanent urethral stents are endoscopically placed. Stents are designed to be incorporated into the wall of the urethra and provide a patent lumen.
The stent is made of corrosion resistant superalloy wire. The woven mesh cylinder is designed to expand inside the urethra and create an open lumen by pressing against the urethral wall with radial force. As urothelial tissue grows over the prosthesis, the mesh becomes incorporated within the urethral wall, providing a flexible and open urethral lumen. Self expanding stents are typically made of metal and are woven or wound like a spring. Synthetic polymer stents of this type are also known in the art. Self-expanding stents are compressed prior to insertion into the delivery device and released by the practitioner when correctly positioned within the stricture site. After release, the stent self expands to a predetermined diameter and is held in place by the expansion force or other physical features of the device.
Benefits of Urethral Stent for Urethral Strictures
- Immediately improves the flow of urine
- Minimizes the recurrence of strictures
- Provides immediate benefits and has been clinically proven to maintain those results over the long term
- Generally, no catheter required after the procedure
- Becomes fully incorporated within the body allows for a full range of endoscopic procedures
- Allows normal ejaculatory function
- Fully compatible with all tissue imaging systems (MRI, X-ray and Ultrasound)
Approximately one-third of all patients undergoing surgery, catheterization or balloon dilation to repair bulbar urethral strictures experience restenosis. In these patients the use of urethral stents has provided satisfactory relief from symptoms. They are most successful in short-length strictures in the bulbous urethra. It may be best reserved for patients who are medically unfit to undergo lengthy open urethral reconstruction procedures.
Placement of stent
Urethral stents are inserted endoscopically after opening the stricture by urethrotomy or sequential dilation. The stent is initially anchored in place through radial force as the stent exerts expansion pressure against the urethral wall. With woven stents epithelial cells lining the urethra begin to grow through the stent's open weave between six and 12 weeks after insertion, thereby permanently securing the stent.
Testing prior to insertion of the urethral stent may consist of performing a urethroscopy or urethrography for visualization of the bladder and urethra to demonstrate the site, length, and number of urethral strictures and urine flow parameters. One to three stents can be inserted; however, usually only one is required. The stent may migrate and/or shorten resulting in incomplete coverage of the stricture. If this occurs, additional stent(s) may be placed or the prosthesis position may be adjusted to assure complete stricture coverage. This procedure is most appropriate when performed in an outpatient setting or inpatient hospital because of the need for anesthesia. The placement procedure can be performed under general or local anesthesia.The urethral stent is not intended as an initial treatment for bulbar urethral strictures nor for the treatment of strictures outside the bulbar urethra.
Contraindications for this indication would include:
For most patients this is a one time process without complication. However, some men experience post insertion complications including stent migration, excessive epithelialization, and stent encrustation. In some cases excessive epithelial tissue may be resected transurethrally. In other situations stent removal may be necessary. Depending on the condition of the stent, removal procedures range from a relatively simple transurethral procedure to open surgery with excision and urethroplasty. All complications increase patent discomfort and health care costs.
Complications occur when a stent is placed distal to the bulbous urethra, causing the patient pain while sitting or during intercourse. Other complications involve migration of the stent. This procedure is contraindicated in patients with dense strictures and in patients with prior substitution urethral reconstruction because it elicits hypertrophic reaction. Other contraindications are :
- Stricture involving the external sphincter;
- Presence of fistula at the proposed prosthesis location;
- Urethral squamous cell carcinoma;
- Perineal urethrostomy;
- Patients with other urethral conditions requiring transurethral manipulations within eight weeks of urethral stent placement;
- Infected, suppurating strictures;
- Meatal or urethral strictures which cannot be opened to 26 Fr. by dilation, urethrotomy or meatotomy; and/or
- Patients with active urinary tract infection.