Ureteral Stenting - A Synopsis

Introduction

Ureteral stents are customized catheters that relieve blockage by preserving the ureteral lumen open and splinting the ureter by functioning as a scaffold to facilitate coordinated tissue healing. Many urological treatments depend on ureteral stents. While stents can be used for various purposes, such as benign prostatic hyperplasia, urethral stricture, or detrusor sphincter dyssynergia are typically employed for diagnostic and therapeutic endoscopic procedures. Although there have been considerable advancements in the design and materials of the stent, infection, and encrustation (a hard layer), remain serious issues when used for a long period.

What Is a Urethral Stent?

The word ‘stent’ can be defined as a thread, rod, or catheter resting inside the lumen of tubular structures, employed to offer support during or after an anastomosis, or to ensure patency of an intact but constricted lumen. Urethral stents are made primarily of a metal alloy, polymeric or biodegradable material and come in a range of forms that are hard enough to keep the urethra open.

What Are the Characteristics of the Ideal Urethral Stent?

• Insertion and removal are easy.

• Biocompatibility (it does not cause a response in the surrounding tissue and is unaffected by the in vivo environment).

• Radiopaque (to facilitate the insertion of the stent using fluoroscopy and to confirm the position of the stent during follow-up radiography).

• Strong enough to alleviate the urethral blockage.

• Resistant to encrustation and infection even after long periods of indwelling

• Mobility to resistance.

• Comfortable for the patient and the physician.

• An internal lumen is large enough to relieve the blockage and allow cystoscopy if necessary.

What Are the Indications of the Urethral Stents?

• In suitable patients, placement of the urethral stents includes urethral stricture disease, benign prostatic hyperplasia (BPH), detrusor-sphincter dyssynergia (DSD), and bladder outlet blockage leading to locally advanced prostate cancer.

• Patients with BPH with a failed medical treatment or those with locally advanced prostate cancer allowing bladder outlet obstruction in which anesthesia can be induced are candidates for urethral stent insertion rather than an indwelling Foley catheter or intermittent catheterization.

• A urethral stent may also assist patients with neurogenic bladder and DSD.

• Endoscopically urethral stents are implanted under either radiologic or cystoscopic supervision and should be readily placed or withdrawn and large enough in diameter to ease urethral blockage and permit cystoscopy if required.

What Are the Contraindications of Urethral Stents?

Contraindications for the placement of the urethral stent include:

• Acute prostatitis (inflammation of the prostate gland).

• An ongoing infection of the urethra or bladder.

• Cystolithiasis (stone in the bladder).

• Penile urethral stricture.

• Stricture affects the external urethral sphincter.

• Recurrent bladder tumors.

• Patients should be assessed with appropriate investigations for the underlying disease process before inserting a urethral stent. Regardless of the reason for the stricture, an extensive anatomical and functional assessment of the urethra should be conducted, including retrograde or antegrade (if a suprapubic catheter is present) urethrography, magnetic resonance imaging (MRI), uroflowmetry, video urodynamic analysis, and cystoscopy. In addition, a urinalysis and culture should be performed to rule out urinary tract infections.

What Are the Types of Urethral Stents?

Several types of urethral stents are available, either temporarily or permanently implanted:

Temporary Stents:

• Temporary urethral stents preserve the lumen of the urethra open and are not integrated into the urethral wall. These stents offer a temporary alternative to an indwelling urethral or suprapubic catheter to treat bladder outlet blockage.

• Temporary urethral stents allow regular micturition and have a 50 to 90 percent success rate. Stainless steel, biodegradable polymers, or a nickel-titanium alloy are used to make temporary stents.

• According to the manufacturer's instructions, temporary urethral stents must be changed every six to 36 months. Some temporary stents are manufactured with biodegradable poly-D or L-lactic acid, which degrades naturally over time.

• Postoperatively, similar stents are utilized with minimally invasive urethral or prostate surgery, such as transurethral microwave treatment (TUMT) and visual laser ablation of the prostate (VLAP), providing temporary drainage and progressive disintegration over time.

• However, cystoscopy for urethral catheterization cannot normally be performed with these stents in situ because of the tiny lumen size.

• Examples of temporary stents include - Urospiral and Prostakath, Memokath, and ProstaCoil.

Temporary Stents Made of Polyurethane Stents:

Polyurethane is used to make three types of temporary stents:

• The Intra-Urethral Catheter (IUC): The intraurethral catheter (IUC) is a 16-18 Fr (French scale measurement system) device that looks like a double-Malecot catheter and comes in lengths ranging from 25 to 80 milimeters. A 22 Fr cystoscope is used to install the device while under local anesthetic and direct eyesight.

• The Barnes Stent: The Barnes stent is a 75 milimeters long 16 Fr urethral device. The stent's proximal end looks like a conventional urethral catheter, while the distal end mimics a Malecot catheter proximal to the verumontanum.

• The Trestle Catheter: The Trestle Catheter comprises two 22 Fr tubes joined by a compressible thread across the sphincter to preserve continence. Under local anesthetic, the catheter is placed and positioned using transrectal ultrasonography.

Permanent Stents:

• As the urothelium covers the device, permanent urethral stents are directed into the urethral lumen and integrated into the urethral wall. In situations with urethral stricture, DSD, or anastomotic stricture following radical prostatectomy, permanent stents relieve bladder outlet blockage.

• A few examples of permanent stents include - UroLume, Memotherm, and Ultraflex.

What Are the Complications of the Ureteral Stents?

• Many risks always accompany the use of urethral stents in urology. Patients requiring cystoscopy to treat and monitor specific urological disorders such as urinary stone disease, transitional cell carcinoma, or any other condition that necessitates recurring endoscopic manipulations should be restricted from receiving certain stent types.

• Since urethral stents are foreign bodies, they might produce irritative urinary symptoms such as frequency, urgency, dysuria (burning during urination), or urge incontinence. In addition, encrustation, stent fracture, migration, urinary tract infections (UTI), hematuria (blood in urine), and clot retention are all possible consequences.

• When a stent is inserted distal to the bulbous urethra, problems might result in incontinence or discomfort while sitting or during intercourse. Other causes for the removal of the stent include worsening of the symptoms, stent encrustation, and inadequate luminal epithelialization were all seen.

Conclusion

Urethral stent implantation may be indicated for various reasons, including urethral stricture illness, BPH, and DSD. Advancement has occurred in the area of urethral stenting over the past decade. As a result, temporary and permanent urethral stents are available for selection. Urethral stenting is a less invasive surgery that can alleviate symptoms of bladder outlet blockage in high-risk surgical patients and as a substitute to open urethroplasty.