Placement of the Urethral Stent Made of Shape Memory Alloy in Management of Benign Prostatic Hypertrophy for Debilitated Patients

0022-5:347/9.5/15431065$03.00/0

THE J O I ~ R N A LOF UROLOGY

Vol. 154,1065-1068, September 1995 Printed in U S A .

Copyright 0 1995 by AMERICAN UROLJXICAL ASSOCIATION,INC.

PLACEMENT OF THE URETHRAL STENT MADE OF SHAPE MEMORY ALLOY IN MANAGEMENT OF BENIGN PROSTATIC HYPERTROPHY FOR DEBILITATED PATIENTS KATSUSHI MORI, SHIGEHIRO OKAMOTO AND MASAO AKIMOTO* From the Gastrointestinal Surgical Unit, Osaka and Division of Urology, St. Luke's Hospital and Nippon Medical School, Tokyo,Japan

ABSTRACT

Purpose: A new urethral stent made of shape memory alloy was placed to relieve prostatic obstruction in 17 patients in whom other approaches were contraindicated. Materials and Methods: All patients were unable to tolerate intervention with sedation and positioning. Placement of the shape memory alloy stent mounted on a 16F Foley catheter is similar to insertion of a urethral catheter except for the heat-sensitive expansion. Results: Each device was easily implanted with the patient on a flat examination table. There was no migration or incrustation of the shape memory alloy stent during the indwelling period. Conclusions: Clinical results demonstrate that the shape memory alloy urethral stent might be the only choice for management of prostatic obstruction in debilitated patients. KEY WORDS:prostatic hyperplasia, urethra, urinary catheterization,bladder neck obstruction Placement of a urethral stent is one of the less invasive modalities for treatment of benign prostatic hypertrophy (BPH),1-4 although its indications and advantages over other less invasive modalities, including medication, remain controversial. Various stainless steel stents are reported as a useful alternative to long-term catheter drainage in patients in whom transurethral resection of the prostate is contraindicated.3-6 However, all patients with an indwelling prostatic stent probably are not fit for other nonoperative procedures or even transurethral resection of the prostate on the basis of guidelines for transurethral resection outlined by a multicenter study.6 Our clinical experience using a new heatsensitive stent made of shape memory alloy7 was strictly limited to patients who were unable to tolerate any treatment except long-term catheter drainage. The ease of placement and removal of the shape memory alloy urethral stent is comparable to that noted with insertion of a Foley catheter.8 Our initial clinical results are de-

scribed with the shape memory alloy urethral stent in patients with BPH unable to undergo other operative or nonoperative procedures. METHODS AND SUBJECTS

Patients. All 17 patients (68to 89 years old) had chronic urinary retention due to BPH and, therefore, had long-term catheter drainage for 2 to 48 months because of the debilitated general condition. The underlying disease contraindicating transurethral resection of the prostate and other minimally invasive treatments was spinal tuberculosis in 1 patient, terminal gastric or liver cancer in 4, mild senile dementia in 3,frequent myocardial infarctions in 3,pacing anythmia in 2 and confined hemiplegia due to stroke in 4. Therefore, all 17 patients were unable to tolerate intervention with sedation and positioning. Patient profiles are shown in the table. Urodynamic study showed various deAcce ted for publication February 10, 1995. grees of detrusor hyperreflexia in the 17 patients who had Realat annual meeting of American urological Association, sari urinary retention before long-term catheter drainage. UriFrancisco, California, May 14-19, 1994. Nippon Medical nary tract infection recurred due to the indwelling urethral *Requests for reprints: Division of Urolo catheter and was occasionally treated with oral antibiotics. School Hospital, 1-1-5 Sendagi, Bunkyo-ward, Kkyo 113, Japan. Patient profiles and followup urodymmic study results R.-Age

Underlying Disease

Mos. Catheter -age

Moa. Followup

UN-68 GS - 72 KK-83 SM - 81 NH-80 NF--89 IT - 86 KE-72 OM - 76 IK - 78 OA - 75 HS - 80 OK - 80 SN - 79 YT-86 MH-78 KS - 86

Spinal tuberculosis Senile dementia Myocardial infarction Hemiplegia Gastric Ca Senile dementia M y d a l infarction Hepatoma Gastric Ca Hemiplegia Hemiplegia Hepatoma Senile dementia Hemiplegia Pacing anytbmia Myocardial infarction Pacing anytbmia

48 10 2 3 2 10 3 2 3 12 2 2 6 4 8 5 2

12 12 12 10 4 10 10 4 6 7 7 4 6 6 5 5 5

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Flow Rate (mllsee.) Meall

Peak

7.1 7.5 6.8 6.9 8.2 6.8 8.7 7.6 7.6 6.5 7.7 6.9 8.7 7.7 8.7 8.7 8.6

10.6 10.4 10.6 8.7 10.9 9.8 11.7 10.9 9.9 8.9 15.7 10.9 15.7 11.7 12.0 11.7 10.9

Residual Vol. (ml.) 20 30 10 40 20 30 0 20 20 30 0 20 0 20 10 10 20

PLACEMENT O F SHAPE MEMOIRY ALLOY URETHRAL STENT

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Placement and removal of the shape memory alloy urethral stent.7 The shape memory alloy stent used consisted of 49.8% nickel, 49.7% titanium and 0.5% iron. A shape memory alloy stent is spiraled by an auto-winding machine at a pitch of 0.3 mm. The subsequent shape achieved is 11 mm. in diameter at the level of the prostatic urethra and 14 mm. in diameter at the level of the bladder outlet. The surface is processed by etching with fluoride and nitrite to avert an oxide film membrane. A suitable length (33, 43 and 53 mm. as measured by ultrasound preoperatively) of the prostatic urethral stent was chosen. Placement was attempted with the patient in a relaxed supine position on a flat examination table (fig. 1, A to D ) . Neither fluoro-

scopic, endoscopic nor ultrasonic guidance was needed for accurate positioning of the shape memory alloy stent, which was confirmed substantially by ultrasonography. When necessary, the stent was removed by cooling it with a flush of cold saline at less than 25C,and then releasing and slowly pulling out the tied loop a t the site of the penile frenulum (fig. 1, El. The shape memory alloy urethral stent was removed in 3 patients in critical condition, all of whom were on terminal care for advanced gastric cancer or unresectable hepatoma. No stent was removed in the remaining 14 patients. Follow up study. Followup included pelvic radiography and urinalysis, and flexible cystoscopy at 3-month intervals, if

A

E

1

FIG 1. A aha memo alloy urethral stent mounted over 16F Foley catheter. B, shape memory alloy urethral stent over 16F Foley cathekris & x e d into7lladder cavity. C, balloon is inflated and later pulled to confirm appropriate engagement of stent after deployment. D, stent is left at full expansion with saline flush of more than 43C.E, shape memory alloy stent is easily pulled out with tied loop string.

PLACEMENT OF SHAPE MEMORY ALLOY URETHRAL STENT

FIG.2. A, oblique pelvic radiographs reveal appropriate indwelling shape memory alloy urethral stent and contrast medium filling bladder immediately after placement (A), and complete emptying of contrast medium from bladder through shape memory alloy urethral

stent (B).

needed. Residual urine volume was determined. The American Urological Association symptom index was used to assess clinical outcome among 17 patients with the shape memory alloy urethral stent. RESULTS

The shape memory alloy urethral stent was placed successfully (fully expanded diameter 11mm.) within a short interval after introduction of a coiled obturator 16F Foley catheter in 17 patients. No bleeding or difficulty with insertion was experienced. To optimize the shape memory alloy stent location, a pulling technique with a balloon was used during the last step of placement to secure tight and precise engagement at the bladder neck and prostatic urethra with the patient on a conventional examination table. This method simultaneously guaranteed distal trapping proximal to the verumontanum with a hooked loop. No sedation was given at placement except for lidocaine jelly used as a lubricant. Subsequent ultrasonography confirmed the correct position of the stent, anchoring from the bladder neck to the proximal portion to the external sphincter through the prostatic urethra. All 17 patients were able to empty the bladder immediately after placement of the shape memory alloy urethral stent (fig. 2). The average symptom score decreased from 19.5 to 7.0 after stent placement. All 17 patients had a negligible residual urine volume (less than 20 ml.) during the observation period. Average and peak flow rates increased from 6.5

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and 8.7 ml. per second to 8.7 to 11.7 ml. per second at 5 and 10 months. All patients tolerated the indwelling stent well. All 17 patients were free of side effects, such as prostatism, dysuria, urinary dribbling and incontinence (see table). Followup urinalysis showed a remarkable decrease in the frequency of urinary tract infection and complete eradication of bacteriuria. Neither migration nor dislodgement was observed during a followup of 4 to 12 months. No replacement was necessary in the 17 patients during followup. Endoscopic examination was done easily with a 17F cystoscope. Fiberscopic findings demonstrated no migration from the original site for 3, 7 and 10 months aRer placement. Moreover, neither incrustation nor fibrotic ingrowth was observed endoscopically at each observation (fig. 3). The stent was removed easily within a short interval from 3 patients in critical condition. No difficulties were encountered during Foley catheter introduction through the stent. Moreover, no gross bleeding or other episode leading to failure of removal was experienced at the time of removal. DISCUSSION

A new urethral stent made of shape memory alloy was designed by our collaborative group.1 Its biocompatibilityand biofunctionality were well demonstrated in canine experiments.? Among urethral stents, the shape memory alloy stent consumed less operative time and accessory equipment necessary for easy placement and removal. Since all currently available urethral stents are placed under fluoroscopic, ultrasonic or endoscopic monitoring, which requires mild sedation and positioning of the patient, these procedures are contraindicated in those with various compromised conditions. None of our patients underwent any minimally invasive modalities except for long-term indwelling catheterization because all of them had serious complications,including tuberculosis related allergy, multiple ischemic heart attacks, hemiplegia secondary to stroke and terminal cancer. The shape memory alloy urethral stent is spiraled over a 16F Foley catheter so that one can place the proximd portion exactly at the bladder neck by inflating the balloon in a blind manner,? while other heat-sensitive5.9.10 and stainless stents must be placed endoscopically or ultrasonographically. Moreover, the shape memory alloy stent was placed in all 17 patients while they were on a flat examination table. Unsuccessful attempts were reported in 6 of 30 patients who received the Memokath,lO since it is dif6cult to locate the anchoring portion of this catheter just proximal to the verumontanum. Because the other nitinol stent needs definite cryogenic handling, it cannot be transferred and stored at an

F!G. 3. Endoscopic views of shape memory alloy urethral stent show accurate positioning in situ at proetatic urethra p sphincter at 3 months (A) and no incrustation or calcification but mucosal covenng at 7 months (B).

d to end

PLACEMENT OF SHAPE MEMORY ALLOY URETHRAL S T E W

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ambient temperature due to a low transforming tempera- through a urethral catheter in 3 patients in critical condition c This removal techhue. Of the procedures cufzently used placement of the due to terminal liver or g a s ~ cancer. &ape memory alloy urethral stent on a 16F Foley catheterll nique ie much simpler than the difficult endoscopic retrieval ie the h e s t , least time+onsuming and most well equipped noted with other stents. These clinical results of relief of prostatic obstruction in methd, and, therefore, it may be the only option for relief of proetatic obstructionin patients with various debilitated con- patients with multiple complications not amenable to minimal invasive treatment are encouraging. Therefore, the diti0m. Neither bleeding nor hematuria occurred during place- shape memory alloy urethral stent might be the most promment of the shape memory alloy urethral stent.Other heat- ising choice for relief of prostatic obstruction in patients with sensitive stents are likely t~ causefrequent bleeding at place- a short life expectancy or in a highly debilitated general ment and removal because they require special endoscopic or condition. Placement of the shape memory alloy urethral semirigid insertion of the catheter.9.10 The shape memory stent awaits a large clinical experience, and various indicaalloy urethral stent mounted on a 16F Foley catheter is easily tions for management of BPH in the mlogical office setting advanced into the bladder and located correctly with tension must be determined. on the inflating balloon immediately after thermal induced &on. REFERENCES Neither migration nor dislodgement was noted in the 17 1. Sarramon, J. P., J o f h , F.,Risehmann,P., busseau, H., El-Din, patients during the indwelling perid, w&& may be A. and Wallaten, H.: prothese endo-urethrale Wallstent dam utsble to cloee engagement of the proximal portion of the les stenoais recidivantes de l'ur6thre. Ann. Urol., 2 3 383, shape memory alloy stent and radial expamion toward the 1989. prostatic urethra*s presumably' a and coiled 2. Nordling, J., Ovesen, H. and Poulsen, A. L.:The intraprostatic shape memory alloy wire 0.5 mm. in diameter may also aid in spiral: clinical resulta in 150 consecutive patients. J. Urol., secure and flexible placement to allow incorporation of the 141:645,1992. hilt into the smooth muscle- pelvic ~ d i o g r a p hrevealed s no 3. McLoughlin, J., Jager, R., Abel, P.D., el Din,k,Adam, A. and change in position despite repeated catheterization for deterWilliams, G.: The uae of prostatic stents in patients with urinary retention who are unfit for surgery. An interim report. mination of residual urine volume. The shape memory alloy Brit. J. Urol., gS:66, 1990. urethral dent became epitheliahed I months after place4. Parra, R. 0.: Titanium urethral & n t an alternative to prostament, migration, altfiough the other heat-mnsitive tectomy in the high surgical risk patient. J. UroL, part 2,146 &nta remainextra-epithelial and often are dislodged before 2394 abstract 106,1991. epithelialization.S.10 However, recent heat-sensitive stenta 5. Qiu, C. Y.,Wang, J. M.,Zhang, Z. X.,Huang, Z. X, Zheng, Q.Y., made of nitinol are not free of migration because of the lack Du, Z. Q.,Liu, M. J. and Liu, C. L.: Stent of shape-memory of etrain absorbance. Unlike the current solution, the shape alloy for urethral obstruction caused by benign prostatic hymemory alloy urethral a n t can avoid migration in the deperplasia. J. Endourol., 8: 65, 1994. ~1OYeasub-parent phase7 because the shape memory alloy 6. Holtgrewe, H.L.,Mebust, w.K, Dowd, J. B., Cockett, A. T.11, wire used is &r and more flexible than any other nitinol Peters, P. C. and Proctor, C.: Transurethral prostatedomy: practice aspects of the dominant operation in American urolstents at body temperature.11 Therefore, neither replacement ogy. J. Urol.,141:248,1989. nor repositioning was required during the indwelling period. 7. Mori, K., Okam~to,S. and Akimoto, M.: A new self-expansive Voiding through the h p e memory alloy urethral stent intraurethral stent using shape memory alloy: a preliminary was painless, free of residual urine and compatible with the report of its availability. Urology, 45: 165, 1995. urinary etream, with and peak O' w rates 8. Mori, K, Okamoto, S. and Akimoto, M.: Placement of the ureafter transurethral resection of the prostate. Moreover, no thralstent made of shape memory alloy (SMA)in the manageproatatism was observed due to the softer nature and less ment of benign prostatic hypertrophy for patients contra-indifiction of the surface against the peripmtatic mthelium, cating other less invasive procedures. J. Urol., part 2, 161: while other stainless and nitinol stenta have rough metal 3984 abstract 682, 1994. surfaces unless they are gilded. Theoretically, an etched ox- 9. Gottfried, H.-W., Hautmann, R. E. Sintermann,R. and Zeehner, 0.: MemothermR stent for BPH treatment in high risk paide membrane surface with physiological electromotive potients-experience of more than 100 cases. J. Urol., part 2, tentid causes no evidence of foreign body reaction, caleifica151:3974 abstract 679,1994. tion or incrustation, which eigniscantly decreased the h n , A. L., schou, J., ovesen, H. and Nordling, J.: 17 patientsduring 10. P oMemokath: infection in a second generation of intraprostatie spirals. Brit. the indwelling period, while much precipitation is likely to J. Urol., 7 2 331, 1993. OCCUI with the other nitinol stent. 11. Mori, K: Stent for biliary, urinary or vascular system. Patent The shape memory alloy urethral stent was easily removed proposal to United StatesDepartment of Commerce 08/190,03, by pulling a loop tie after cooling with a cold saline flush 1994.

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