BOO ? How common  ?

Bladder outflow obstruction (BOO) due to benign prostatic enlargement is the commonest cause of lower urinary tract symptoms in the elderly male. Benign Prostatic Hyperplasia (BPH) occurs histologically in approximately 50% of men at the age of 60 and in nearly 100% of men by 80 years. The prevalence of clinical BPH, defined as an enlargement of the prostate gland to a weight of more than 20g in the presence of symptoms and/or a urinary flow rate of less than 15ml/s and without evidence of malignancy. ?It has been estimated that in USA the chance of a 40-years old man subsequently requiring a prostatectomy is approximately 29%?.

The Gold Standard

Transurethral resection of the prostate (TURP) is still the traditional therapy of choice for symptomatic BPH and represents the ?gold standard? against which other therapies need to be judged. Although mortality of TURP has been decreasing over the years, it is still significant and increases with age from 0.4% in the 65-69 years age group to 3.5% in those older than 85 years. This is associated with a significant morbidity of about 18%, which includes a 1% risk of total incontinence, a 2.1% risk of stress incontinence, 1.7% risk of Bladder neck contracture and a 3.1% risk of urethral stricture. Other common post-operative problems include urinary infection, testicular infection, impotence and the need for blood transfusions.
 

Furthermore, outcome studies reveal that about 20% of patients fail to achieve improvement in their voiding symptoms following prostatectomy and 15% of patients require re-operation for stricture, bladder neck contracture, recurrent ?prostatism? or other problems within 8 years of surgery. These factors, coupled with increased public awareness of alternative non-surgical or minimally invasive treatment options, have raised a number of questions as to the appropriate therapy for BPH in contemporary practice. In addition, since BPH with urinary discomfort and retention is often a disease of elderly patients, coexisting severe disease sometimes render surgery a life-threatening procedure. With a growing elderly population, unfit males presenting with severe lower urinary tract symptoms or urinary retention due to BOO are likely to pose an increasing management problem. When a patient is either temporarily or permanently unfit for surgery, or surgery has to be postponed for other technical reasons, other alleviating steps are required. Many patients ultimately have an indwelling Foley catheter for prolonged periods; others suffer the misery of nocturia, day time frequency and possibly dribbling.

Indwelling Foley?s Catheter ? The Problems !

The main reason for leaving an indwelling catheter in place for the prolonged period is to relieve urinary retention. The damage caused by permanent indwelling urinary catheter, as well as the discomfort imposed on the patients, are well documented in the literature. The risk of acquiring infection increase linearly with the number of days the catheter is left in place. Catheter associated bacteriuria accounts for 40% of annual nosocomial infections. The incidence of bacteriuria associated with indwelling urethral catheterization increases by about 5 % per day. Thus, bacteriuria universally develops within 3-4 weeks, even when closed urinary drainage is strictly used.

Search for an alternative !

Fabian was the first to report on the use of stents in the prostatic urethra. He developed a stainless steel coil instead of an indwelling catheter for the management of severe prostatic obstruction in two patients to relieve their urinary retention, and named this device a ?Partial Catheter? or ?Urological Spiral?. Since then, several modifications have been made and put into clinical use.

Subsequently, this stent, and other new intra-urethral devices that were introduced for urological use, gained increasing acceptance in daily urological practice. These were intraluminal devices that were left temporarily in the prostatic urethra and then either removed or replaced with a new one. One of these modified prostatic stents developed during the late 1980s was the Prostakath, which is based on the Fabian stent but is gold plated.

Although these stents acted as an excellent alternative to an indwelling catheter, they had the major problem of distal and proximal, partial or complete migration, and could not be used in the anterior urethra. The search for a better stent gave birth to a new stent concept for use in urethral strictures. In order to prevent the problems of the first generation stents, the first large calibre UroCoil stent was developed and tested in 1989. Differing from the first generation stents, which had a fixed 21 Fr caliber( 7 mm outer diameter) and a smooth surface, this new stent was designed to change its shape to a wavy outline and self-expand to a caliber of 24/30 Fr ( 8-10 mm outer diameter) after deployment, in order to prevent migration.

 Shortly afterwards, and based on the same principle, the ProstaCoil was developed for use in the prostatic urethra. Like the UroCoil System stents, the ProstaCoil was made of a shape memory nickel-titanium alloy, best known as Nitinol or Ni-Ti.

Later, stents developed for vascular use were adapted for permanent implantation into the prostatic urethra. An example of permanent intra-urethral stent is the Urolume stent, which was originally developed for endovascular use by Hans Wallsten, a Swiss national, for the prevention of stenosis after transluminal angioplasty, and was initially called ?Wallstent?. It is now called the Urolume and is manufactured by American Medical Systems, Minnetonka, Minnesota, USA. It has been used successfully in urinary tract for the treatment of urethral stricture and subsequently for the treatment of BPH in patients not fit to undergo TURP. These expandable tubular stents for stainless steel mesh are to remain permanently in the prostatic urethra and their structure allows epithelium to grow and cover the stent.

IDEAL PROSTATIC STENT:

During the third international Consultation on Benign Prostatic Hyperplasia, 1995, the following criteria were finalized.

An ideal stent should:

• Be easy to insert and position under topical urethral anesthesia
• Have free lumen large enough to alleviate the obstruction
• Cause no sphincter involvement
• Be malleable to conform the shape of the prostatic urethra
• Not result in creation of tissue reaction or infection
• Cause no encrustation even after long indwelling time
• Not migrate once in position
• Have free lumen large enough to allow cystoscopy
• Be easy to remove if required
• Be inexpensive.

INDICATIONS OF STENTING

All patients with benign or malignant prostatic obstruction and who require insertion of an indwelling catheter are candidate for stent insertion. Furthermore, in patient who have an absolute indication for TURP, such as those with a large volume of residual urine, or upper urinary tract deterioration, but who are not suitable for surgery because of concomitant conditions and thus fall into category ASA IV, stents can be used as an alternative to surgery.

Temporary prostatic stents/intra-urethral catheters have been used successfully to relive retention of urine in those considered unfit for surgery. Other indications for temporary prostatic stenting are a trial of stenting (prior to the insertion of a ?permanent? stent), temporary relief of obstruction while waiting for the effect of other therapies (such as thermal / coagulative treatments of the prostate), or hormonal manipulation in carcinoma of the prostate and while waiting for other medial conditions to resolve.

A distinct group of patients in whom the stents can be used comprises those younger patients in whom prostate surgery is indicated but who refuse it because of fear of potential loss of fertility as a result of retrograde ejaculation, or the possible loss of potency, following transurethral prostatic resection.

Also, in the context of public medicine where the waiting period for surgery may be prolonged, patients could be temporarily relieved of the discomfort of an indwelling urinary catheter by an intra-uretheral catheter.

ADVANTAGES

The use of prostatic stents appears to have a number of advantages, these include; a short operating time, minimal blood loss, ease of insertion, a short hospital stay, no indwelling catheter & immediate relief of obstruction. In addition, stents offer the benefit of insertion and removal under local anesthesia, reversibility of the technique, and the absence of any of the expensive equipment that is often required in other alternative minimally invasive therapies.

In spite of the fact that an indwelling catheter is not an impediment for the appearance of penile erection, bearing one, makes it impossible to perform sexually. Moreover, it is a serious psychological burden for the patient himself, causing depression for becoming impotent, and loss of dignity towards his female partner for not being able to satisfy her sexual needs. On the other hand patients with intra-urethral stents do not have any external appliances and may continue with their normal life, including sexual activity.

FOLLOW-UP EVALUATION

During the indwelling period of the stent it is advisable to acidify the urine (pH below 6) and maintain a urine output of 1500-2000 ml/day to prevent urinary tract infection (UTI) and reduce encrustations. Monthly urine cultures and appropriate antibiotics are prescribed, especially to patients who had a chronic infection before stenting or who develop clinically significant UTI.

Cost comparison of long-term catheterization and prostatic stenting

With regard to affordability, though prostatic stenting has been considered an expensive alternative to catheterization owing to its initial cost, it has been shown that the cost of maintaining a patient with a permanent indwelling catheter for 1 year equals that of a Memokath (temporary metallic stent) treatment.

Many elderly men are treated by long-term catheterization in the community with continuing care form the district nursing service. Contact with the urology team occurs only occasionally when major problems arise, but minor problems are frequent and can cause considerable suffering. The cost of large number of district nursing service visits to patients with long-term catheter is consequently enormous, and in a study conducted in London in 1995, it totaled approximately pounds 700 per patient per annum. This assessment of male patients in the community shows that long-term catheterization may not provide optimal care and is often very expensive. Prostatic stenting therefore appears to offer an improved clinical alternative that is also viable in terms of cost.

In addition, the question of the relatively higher cost in comparison to the standard Foley catheter has to be weighed with the known increase risks of infection and stricture formation while using the latter. Thus in the long run, intra-urethral stents are more economical than indwelling catheters, saving costs on catheters, urine bags, antibiotics, trained personnel and probably hospitalization for severe infections and their complications. No doubt, extensive use, technical advances and free competition will make these devices more attractive to both patients and urologists.

Last but not least, although the insertion procedure looks very simple on the videos prepared by all stent manufactures, in reality it is not. Correct measurement of the length of the stent required and correct placement of the stent should be an easy procedure, but it is not. For successful stent insertion, a skilled endoscopic surgeon is recommended who will also have to traverse the individual learning curve.