1
Thermo-expandable prostatic stent for management of acute urinary retention secondary to benign prostatic hyperplasiain high risk patients
Tarek El-Karamany, M.D.; Ahmed Abou Taleb, M.D.; Ashraf AbdelAal, M.D.;andAhmed Abdel Baky, M.D.
Department of Urology, Benha Faculty of Medicine,Egypt
Abstract
Purpose:To evaluate the thermo-expandable prostaticstent(Memokath)in patients presenting in acute urinary retention(AUR) secondary to benignprostatic hyperplasia(BPH).
Materials and Methods:From October 2007 to August 2009, 40 patients at high risk anaesthesiologically who had developed AURsecondary to BPHunderwentMemokathstent insertion. The stents were inserted in an outpatient setting under local anaesthesia or brief regional block.The patients were evaluated by physical examination, digital rectal examination(DRE), symptom evaluation using the International Prostate Symptom Score Questionnaire(IPSS),uroflowmetry, and postvoidresidual(PVR) urinevolume measurement.The patients were evaluated at baseline and at 2 weeks,1, 3 ,6,and 12 months after stent placement.
Results: Stents were successfully inserted in all patients. Spontaneous voiding was achieved in all patients.The peak urinary flow rate(Qmax),PVR urine volume, and IPSS and quality of life(QOL) score were significantly improvedafter procedure and continued to improve during subsequent follow-up. At 12 month,IPSS had improved from 26.1 (range18-35) to 14.8 (range 3-28; P = 0.031),andQOL score had improved from 5.2 (range 2-6) to 2.1 (range 0-4); P= 0.04. The PVR urine volume had decreased from 570 ml(range 420-710) to 79 ml (range 25-330); P= 0.002. The Qmax increased from 0 to 12.3 ml; P <0.0001.The main complications were urge incontinence (15%)and stent migration (7.5%).The main reason for removal of the stent was worsening of symptoms(5%).
Conclusions:Memokath prostatic stent represents a safe and effective treatment option for patients with BPH presenting with AUR.It has low morbidity and provides immediate symptoms and voiding improvement.
Key words: Memokath, Acute urinary retention,Benign prostatic hyperplasia,Urethra.
Introduction
It is estimated that about 50% of men will develop lower urinary tract symptoms (LUTS) secondary to BPH in the sixth decade of life (1).Acute urinary retention is a dire complication of BPH and is an indication for surgery in about 25% to 30% of patients undergoing transurethral resectionof the prostate(2).Many patients with AUR secondary toBPH who are either refuse or surgically unfit for prostatectomy are treated with indwelling catheterization. The complications of indwelling catheterization are well-known (3). To overcome these difficulties alternative treatment options have been developed, one of which is prostatic stents.
The first generation stents were either epithelializing (Urolume Wall- stent, American Medical System , Minnetonka, MN)or non- epithelializing (Prostakath, Engineers and Doctors A/S, Copenhagen, Denmark) (4).Urolume stent allows the urothelium to grow over it,however, rates of infection, encrustation and migration were high, also progressive narrowing occurred due to epithelial growth that mandates stent removal. Such removal can be difficult and usually requires general anesthesia (5).Prostakath were designed for short symptom relief of bladder outlet obstruction. Long term data on these stents were discouraging, with approximately 50% removal rate within the first year (6).Consequently,thethermo-expandable metallic stents (Memokath) were developed. Memokath has been available since 1992(7). Its first use wasdescribed by Poulsen et al (8).
The aim of the present study was to evaluate prospectively efficacy and safetyof Memokath stent for long-term relief of AURsecondary to BPH in men deemed high surgical risk.
Materials and Methods
From October 2007 to August 2009,40 patients with AUR secondary to BPH were treated at urology department,Benha university hospital with Memokath stent. The study was approved by the scientific committee of Benha faculty of medicine.
The preoperative evaluation included symptoms assessment using IPSS andQOL scorefor the period before the episode of retention,physical examination with a focused neurological examination and DRE, prostate volume measurementusing transrectal ultrasoundand prostate specific antigen determination,with ultrasound-guided biopsy when indicated.All patients underwent a trial of voiding without catheter during alpha-blocker therapy, and PVR urine volume was measured.The exclusion criteria included neurogenic bladder, chronic urinary retention, urethral stricture, prostate cancer and past or current history of urothelial malignancy or urolithiasis.The IPSS uses the 7 questions as the AUA- Symptom Index with the addition of disease specific quality of life question,scored on a scale from 0-6 points(delighted to terrible)(10).
The American Society of Anesthesiologists (ASA)physical status were assessed by the anesthetists.Five patients were ASA grade 2,twenty five were grade 3 and 10 were grade 4(Table 1).
Table 1: ASA grades of 40stentedpatients.
ASA grade* / Description / No.pts(%)1 / A normal healthy patient / 0
2 / A patient with mild systemic disease / 5(12.5%)
3 / Apatient with severe systemic disease / 25(62.5%)
4 / A patient with severe systemic disease that is constant threat to life / 10(25%)
5 / A moribund patient who is not expected to survive without the operation / 0
6 / A declared brain-dead patient / 0
*ASA physical status classification system,source:ASA website.Grade2 patients refused TURP
Follow-up evaluations were performed directly after placement of the stent and at 14 days and 1,3,6 and 12 months post procedure. The follow- up included the IPSS and QOL questionnaire, uroflowmetry, evaluation of the stent positionandPVR urine volume measurement using trans-abdominal ultrasonography.
The mean values ofQmax, PVR urine volume, IPSS and QOL score were compared with the preoperative values using a paired student t-test with P< 0.05 considered significant.
Memokath stent:
The Memokath stent (Engineers and Doctors A/S, Copenhagen, Denmark) is thermo-expandable nickel-titanium alloy. The alloy has two forms, namely martensite and austenite. As the structure of one of these components is floppy and the other is rigid, this combination gives the Memokath stent a (shape memory). This means that the stent becomes soft when flushed with cold saline (5-10°c) but returns to a preformed shape when warmed to 45-50°c. This feature allows its easy insertion and removal.
In addition, the stent has a closed tight spiral structure that prevent urothelial ingrowth and thus again facilitate easy removal if required. It is available in length from 3-7 cm and expands to 24 Fr. with distal cone like end of 44 Fr. to lock it in position(Fig.1).
Technique:
The procedure took place in an outpatient setting under local anesthesia augmented with sedoanalgesiain 25 patients and under saddle block in 15 patients who couldn't tolerate the procedure under local anesthesia.
Urethrocystoscopy was performed with 25Fr rigid cystoscope to ensure that the stentwill pass without hindrance. Cystoscope is held at the bladder neck and a marker is placed on the sheath at the tip of the penis. Cystoscope is withdrawn just below the verumontanum and another marker is placed. The distance between the markers equals the length of the stent required. The stent on its introducing sheath is mounted onto the cystoscope lens so that the tip of the cystoscope is clear of the stent by 2-3 mm.The delivery system is advanced into the urethra until the tip of the cystoscope lens just enters the bladder. At approximately 0.5 cm beyond the bladder neck, the stent was released by irrigation with about 50 ml hot saline. This expands the lower 4-6 mm of the stent to 44 Fr that fixes it into position. The cystoscope is gently withdrawn through the stent while verifying position of its distal end and the delivery system is removed(Fig.2 a,b).
Repositioning of the stent can be accomplished easily first by flushing it with cold saline and pushing it by cystoscope sheath upward for distal migration or by pulling it with a grasping forceps for proximal migration. Once in its correct position, the stent is irrigated with warm saline to be fully expanded (Fig.3). Removal of the stent was performed under local anesthesia after which cystoscope was inserted. The stent was irrigated with cold saline to becomesoft. Under direct vision, the stent was grasped with a forceps and pulled outside (Fig.4).
Figure 1:Memokath 028 thermo-expandable prostatic stent.
( Fig2a)
(Fig2b)
Figure2:Assessment of stent position by urethrocystoscopy at the end of the procedure(a),andby plain radiograph during follow-up visits(b).
Fig. 3
Repositioning ofaproximally
migrated stent by a grasping forceps
Fig. 4Memokath after extraction.
Results
Fourtypatients with a mean age of 72.6 years (range 63 to 84) presented with AUR secondary toBPH were unfit for surgery.The main risk factors were ischemic heart disease, severe chronic obstructive pulmonary disease and cerebrovascular accidents. Indwelling catheters had been placed in 38 of the 40 patients for more than 2 months because they had failed repeated voiding attempts. The remaining 2 patients had been receiving clean intermittent catheterization. Prostate volume ranged from 37 to 80 gm with mean of 65.7. Table (1) summarizes the patients' demographics.Stentswere successfully implanted in all patients. The operative time ranged from 25-40 minutes (mean 27.4). Endoscopy at the end of the procedure showed that all stents were properly placed and expanded. All patients started to void on the same day of stent insertion. All patients had transient Haematuria which resolved within few hours.
Of 40 patients enrolled, 18(45%) completed the 12 months post procedure follow-up.Eight patients (20%) died during follow-up period due to significant co-morbidities not related to the procedure.All had functioning stents till their death. Fourteen patients (35%) lost to follow-up.Cultural factors and inability of the patients to attend the hospital for evaluations contributed to loss of follow-up.
The Qmax, PVR urine volume, IPSS and QOL score were significantly improved throughout the follow up period (Table 2).At 12 months, IPSS had improved from 26.1 (range 18 to35 ) to 14.8 (range 3to28)and QOL score had improved from 5.2(range 2to6)to 2.1(range 0 to 4) . The PVR urine volume had decreased from 570 ml (range 420-710) to 79 ml(range 25 to330ml ).The mean Qmax increased from 0 to 12.3ml/sec. However, the mean Qmax and PVR urine volume showed significant decline at 12 months compared to 1 month values.
After stent insertion, 36 patients developed dysuria and irritative symptoms which improved gradually with time. Six patients (15%) reported urge urinary incontinence,4 respond to anti-cholinergic therapy and 2 required stent repositioning due to partial migration. Four patients (10%) experienced urinary tract infection, at 1 month in 3 patients,andat 6 months in 1. All responded promptly to oral antibiotic therapy. Stent migration occurred in 3 patients at 7,8 and 11 month post procedure. Repositioning took place successfully in 2 patients in an outpatient setting and stent removal was performed in one patient.
The main reason for stent removal was worsening of symptoms. Two patients complained of severe irritative and obstructive symptoms with marked PVR (>300ml). They were treated with stent removal and indwelling urethral catheters. Stent removal was uneventful and performed under local anesthesia and sedation. Encrustation on the stent was not seen in any patient.
Table2:Patients' demographics.
- Age (years) Mean ±SD( Range )
- Prostate volume,cc, Mean±SD (Range)
Concomitant disease (no.pts)
- Ischemic heart disease/Heart failure
- Chronic Obstructive lung disease
- Cerebral infarction
- Liver cell failure
12
8
6
Urethral Catheterization
- Urethral catheter
- Clean intermittent
2
Table 3 : Baseline data and follow- up changes after Memokathinsertion
VariableMean ± SD
(range) / Time points of follow-up (no.pts)
Baseline (n = 40) / 2 W (n = 40) / 1m (n = 36) / 3m ( n=28) / P value / 6mn( no=22) / P value / 1 year(no=18) / Pvalue
Q max (m1/s)
P value / 0 / 13.7±3.8
(10.2-17.5)
<0.0001٭ / 16.1±2.1
(8.9-19.2)
<0.0001٭ / 15.9±3.1
(8.4-18.9)
<0.0001٭ / 0.478 / 14.1±2.5(6.1-16.7)
<0.0001٭ / 0.04٭٭ / 12.3±1.1
(5.6-15.1)
<0.0001٭ / 0.037٭٭
PVR (m1)
P value / 570±8.2
(420-710) / 75±40
(12-80)
<0.0001٭ / 96.8±110
(15-95)
<0.0001٭ / 80.1±60
(25-180)
<0.001٭ / 0.341 / 85±72
(30-350)
<0.001٭ / 0.08 / 79±109
(25-330)
0.002٭ / 0.02٭٭
IPSS
P value / 26.1±7
(18-35) / 16.9±1.9
(6-20)
0.02٭ / 12.5±5
(4-21)
0.01٭ / 11.8±6
(3-21)
0.01٭ / 0.252 / 13.7±8
(2-26)
0.01٭ / 0.18 / 14.8±9
(3-28)
0.031٭ / 0.650
Qo L
P value / 5.2±0.7
(2-6) / 2.3±0.8
(1-5)
0.02٭ / 1.4±0.5
(0-4)
0.016٭ / 1.3±0.4
(1-4)
0.011٭ / 0.137 / 1.8±0.9
(1-3)
0.018٭ / 0.731 / 2.1±0.3
(0-4)
0.04٭ / 0.486
P٭<0.05 compared to baseline values
P٭٭<0.05 compared to values at 1 m
Discussion
Conventional TURP remains the reference standard treatment of symptomatic BPH and is the treatment of choice for men with urinary retention. However, the operative risk is often increased due to co-morbidity and for some patients TURP present unacceptable surgical risks (11,12).Great efforts have been made in the last few years to develop minimally invasive treatment alternatives for patients with urinary retention who are not suitable for surgical therapy. Among these minimally invasive treatments are thermotherapy, transurethral needle ablation of the prostate, ethanol injection therapy and prostatic stents. Transurethral microwave thermotherapy is a safe well tolerated treatment for patients in AUR with high surgical risk. However, the re-treatment rate has been high (26%-31%), with a long catheterization time (mean 21 days), high percentage of urinary tract infection (17.9%), and the presence of irritative symptoms, which developed in all patients (12,13). Transurethral needle ablation of the prostate is a safe treatment in patients with AUR, but with high failure rate (13.1% to 25%) (14), and ethanol injection therapy has 23.8 % failure rate(15).
The ideal prostatic stent should be easy to insert and remove, biocompatible, radio-opaque, durable, resistant to encrustation and infection, and has lumen large enough to alleviate the obstruction and facilitate cystoscopy if needed. Placement of Memokath was easy. It was performed on an ambulant setting under local anaesthesia or brief regional block. Stent removal was easier than insertion, it was performed under local anesthesiain all patients. These results are comparable with the former studies with the Memokath stent (16,17).
Since the first description of prostatic stents by Fabian in 1980 (18), migration has been a significant problem in various stent design. Migration was particularly a problem in the non-expandable spiral stents (10% to 38%) (19). Polyurethane stents such as Spanner and Trestle stents have migration rate of 0% to 21% (20,21). Even though, migration of permanent epithelializing stents like Urolume did occasionally occur (4% to 6%) (22).Reports on thermo-expandable stents demonstrate that migration rate is related to stent shape. Hourglass thermo-expandable nitinol stent migrated in 93% of patients, while migration rate of bell-shaped stent was 15% (23,24).While the Memokath stent had a lower migration rate (0-13%) (8,16). In the present study, stent migration occurred in 7.5% of patients. Endoscopic repositioning was possible in 2 patients.
Reports on both 1st generation and 2nd generation spiral stents showed immediate spontaneous voiding in 82% to 100% (6,7) Other types of prostatic stents also allowed spontaneous voiding and improvement in Qmax and PVR volume in most patients(24,25,26). Several studies have confirmed the safety and efficacy of Memokath stent in the treatment of men with symptomatic BPH(8,16,27).Perry et al(16) found significant improvements in IPSS & QOL scores after placement of the Memokath stent that changed little over time.In the current study, placement of Memokath resulted in immediate spontaneous voiding in all patients. Improvement was seen in the Qmax, PVR urine volume, IPSS and QOL score during the 12 months after procedure.Other types of prostatic stents also allowed spontaneous voiding and improvement in Qmax and PVR urine volume in most patients (24,25). As in the present study, however in some of these trials, a tendency toward a decrease in Qmax during follow up was observed (8,26).
In Egypt the cost of the stent alone is about 6000 LE,and this cost limits the widespread utilization of the stent.So,we selected a smallsubgroup of elderly patients who presented with acute urinary retention, and were not suitable to undergo TURP.
In papers on prostatic stents, urge incontinence was described in 0-23% of the patients (20,25,28). Displacement of the stent which could sometimes be resolved by cystoscopical repositioning of the stent, was mentioned as a possible reason (29).The main complications encountered in this trial were urge incontinence.Possible causes are detrusal instability after prolonged obstruction, foreign body irritation of the external sphincter and or stent migration. Urge incontinence often responded to anti-cholinergics.
Lee et al(27), treated 15 patients with AUR secondary to BPH with Memokath stentand reported 20% failure rate (2 patients)due to stent migration (13%) and outgrowing prostatic tissue (7%).In the current study,the Memokath stent failed in 3 patients due to worsening of symptoms in 2 patients. Those patients were noted to have large baseline PVR (>680 ml) and significant median lobe hypertrophy. They were treated by stent removal and indwelling catheter.The stent was removed in the third patient due to failure of repositioning after proximal migration.The excellent durability and safety encountered in this study make the Memokath stent attractive for clinical applications.
Conclusions
The results of the present study have demonstrated the safety and efficacy of Memokath stent in treatment of high surgical risk patients with BPH presenting in AUR. Memokath stent is easy to insert and remove under local anaesthesia. It immediately improves voiding function and significantly alleviates symptoms.
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