Radiology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Published online before print December 11, 2002, 10.1148/radiol.2262012160
This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
2262012160v1
226/2/433    most recent
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Song, H.-Y.
Right arrow Articles by Park, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Song, H.-Y.
Right arrow Articles by Park, T.
(Radiology 2003;226:433-440.)
© RSNA, 2003

Vascular and Interventional Radiology

Recurrent Traumatic Urethral Strictures near the External Sphincter: Treatment with a Covered, Retrievable, Expandable Nitinol Stent—Initial Results1

Ho-Young Song, MD, Hyungkeun Park, MD, Tae-Suk Suh, MD, Gi-Young Ko, MD, Tae-Hyung Kim, BS, Eun-Sang Kim, BS and Taehan Park, MD

1 From the Departments of Diagnostic Radiology (H.Y.S., T.S.S., G.Y.K.), Urology (H.P., T.P.), and Biomedical Engineering (T.H.K., E.S.K.), Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-dong, Songpa-gu, Seoul 138-736, Korea. From the 2000 RSNA scientific assembly. Received January 14, 2002; revision requested March 5; revision received May 3; accepted June 3. Supported by grant HMP-98-G-2-043 from the HAN (Highly Advanced National) Project, Ministry of Health and Welfare, Republic of Korea. Address correspondence to H.Y.S. (e-mail: hysong@www.amc.seoul.kr).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
PURPOSE: To investigate the clinical effectiveness of a covered, retrievable, expandable nitinol stent in treating traumatic urethral strictures near the external sphincter.

MATERIALS AND METHODS: The stent was 10 mm in diameter when fully expanded and 40–50 mm long. To make it removable, two nylon drawstrings were attached to its lower inner margin. Twelve consecutive men (19–67 years; mean age, 47 years) with traumatic urethral strictures near the external sphincter that were refractory to endoscopic urethrotomy were treated. With fluoroscopic guidance, a stent was placed to completely bridge the external sphincter. The stent was electively removed with a retrieval hook wire 2 months after placement. Stent placement and removal were successful in all patients, with no procedural complications.

RESULTS: Mean maximum urine flow rate was 5 mL/sec (range, 3–7 mL/sec) before stent placement and 27 mL/sec (range, 16–40 mL/sec) at 1 week after placement. During the mean follow-up of 20 months (range, 2–37 months) after the first stent removal, strictures recurred in eight of 12 patients. For the eight patients with recurrence, a second stent was placed and 4 months later was removed from seven of the eight patients. During the mean follow-up of 18 months (range, 4–32 months) after the second stent removal, strictures recurred in two patients, in whom a third stent was placed and then removed 4 months later, with good results. Four (33%) of 12 patients, five (62%) of eight patients, and two (100%) of two patients were successfully treated with placement of the first stent, the second stent, and the third stent, respectively. In the remaining patient, the second stent remains in place.

CONCLUSION: Placement of a covered, retrievable, expandable nitinol stent seems to be effective in treating urethral strictures near the external sphincter and warrants further investigation.

© RSNA, 2003

Index terms: Genitourinary system, injuries, 84.43 • Urethra, interventional procedures, 84.1269 • Urethra, stenosis or obstruction, 84.847


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
Despite recent developments in endoscopic and reconstructive urology, the management of urethral strictures remains a challenge to urologists (1–4). Endoscopic urethrotomy remains the primary treatment, but 46%–76% of strictures recur within 2 years, and the treatment of recurrent strictures involves an even greater risk of further recurrences (4,5). In addition, the option of repeated self-catheterization to maintain a satisfactory urethral lumen after endoscopic optical urethrotomy is not accepted by many patients (1). The essential problem is how to prevent the edges of the cut stricture from adhering together and the scar from shrinking (4). To solve the problem, the placement of metallic urethral stents permanently (1,6–14) or temporarily (2,3,15,16) has been introduced, with good initial results. Metallic stents, however, can migrate and cause local pain, discomfort, and hyperplastic proliferation of the mucosa. Once the permanent stent is incorporated into the periurethral tissues, it can only be removed surgically (5).

Moreover, the treatment of urethral strictures near the external sphincter remains a challenge to urologists, as well as to interventional radiologists, because stent placement may compromise sphincter function (2,3,9). To keep the sphincter function intact, as well as to eliminate the strictures, we designed a polyurethane-covered, retrievable, expandable nitinol stent and a device for the removal of the stent. The purpose of this study was to investigate the feasibility and clinical effectiveness of the stent and its retrieval device in the treatment of urethral strictures near the external sphincter.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
Indications for Stent Placement
During the period of October 1998 to July 2001, 12 consecutive patients with failed urethrotomies for traumatic urethral strictures near the external sphincter were treated with the fluoroscopically guided placement of a covered, retrievable, expandable nitinol stent. Their urethral strictures had been treated in the past with a minimum of two unsuccessful endoscopic optical urethrotomies. In all patients, the causes of urethral strictures were either traffic accidents or falling. The site of the stricture was at the posterior urethra, near the external sphincter, in all patients. The mean length of the stricture was 23 mm (range, 15–30 mm). The mean duration of symptoms was 9 months (range, 4–16 months). All patients underwent preprocedural urodynamic studies. The mean maximum urine flow rate before stent placement was 5 mL/sec (range, 3–7 mL/sec).

There were 12 male patients, aged 19–67 years (mean age, 47 years). All patients had undergone the last urethrotomy, with recurrence, 2–6 weeks before stent placement. One of them had infected urine. A total of 22 stents were placed during 22 stent insertion procedures in the 12 patients. All 12 patients initially underwent placement of only one stent; one or two additional stents were placed in eight of the 12 patients because of recurrent strictures after the removal of the stent. All patients provided fully informed consent to undergo this new treatment, and the study protocol was approved by the hospital ethics committee.

Stent Construction
The stent was woven 16 times from a single thread of 0.1-mm-diameter nitinol wire filament in a tubular configuration. The stent has 16 bent points on the upper and lower end portions. To prevent mucosal hyperplasia through the stent wires, the stent was covered by using a dipping method with a 12% polyurethane solution (Chronoflex; Cardiotech International, Woburn, Mass). To provide a firmer covering to the most proximal and distal parts of the stent, those areas were covered with 100% nylon mesh and then coated by dipping them into polyurethane solution (Fig 1). The stent was 10 mm in diameter when fully expanded and 40–50 mm long. Radiopaque markers were attached at two points 180° apart on the circumference of the stent at both ends (Fig 2). The radiopaque marker was made by tying a 0.3-mm gold wire six times around the bent portion.



View larger version (107K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 1. Top to bottom: covered retrievable nitinol stent, sheath with dilator and guide wire, pusher catheter, and hook wire.

 


View larger version (42K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 2. Diagram shows two drawstrings (2) attached to lower inner margin of stent. 1 = central lumen, 3 = nylon loop, 4 = upper margin of wire, 5 = radiopaque markers.

 
To make the stent removable, two drawstrings made from nylon monofilament were attached to the lower inner margin of the stent (Fig 2). A nylon loop 2 mm in diameter was hooked inside each bend of the proximal end of the stent and secured with a suture. Another nylon thread was passed through each of these small nylon loops to form a larger loop (a drawstring) that filled the circumference of the inside of the stent. The resulting large loop was tied up. We constructed the stent in our research laboratory.

Stent Introducer Set and Retrieval Set
A stent introducer set (Fig 1) consists of a 9-F braided sheath, a dilator, and a pusher catheter (Cook, Bloomington, Ind). The stent retrieval set (Fig 1) consists of a 9-F braided sheath, a dilator (Cook), and a hook wire. We constructed the hook wire in our research laboratory out of a stainless steel wire. The end of the hook wire was constructed in a question-mark configuration to hook the drawstring of the stent. The distal 20-mm section of the question-mark portion was positioned at an angle of about 30° to the axis. An additional bend was made in this section with the use of pliers so that the hook would not catch the end of the sheath when the hook was being withdrawn.

Stent Placement Technique
Stent placement and removal were performed by one author (H.Y.S.). Before stent placement, the site, severity, and length of the stricture were evaluated with urethrography and uroflowmetry. Oral prophylactic antibiotic therapy was begun 1 day before the procedure and was continued for at least 7 days. The patient was not sedated before the stent insertion procedure. The patient was placed in a left anterior oblique position with knees bent. After disinfection of the external urethral orifice with 0.05% chlorhexidine, the urethra was anesthetized topically with 10 mL of lubricating jelly containing 2% lidocaine. Retrograde urethrography was performed with fluoroscopic guidance, and the sites of the stricture and the external sphincter were marked on the skin of the patient.

A 0.035-inch guide wire (Radiofocus M; Terumo, Tokyo, Japan) was inserted through the urethra across the stricture into the urinary bladder with fluoroscopic guidance. A straight 5-F graduated sizing catheter (Cook) was passed over the guide wire to the proximal part of the stricture to measure the length of the stricture. A stent at least 20 mm longer than the stricture was selected for placement so that the proximal and distal parts of the stent would rest on the upper and lower margins of the stricture, respectively. A 9-F sheath with a dilator was passed over the guide wire into the urethra and was advanced until the proximal tip of the sheath reached at least 1 cm beyond the stricture (Fig 3). After the dilator and the guide wire were removed from the sheath, the stent was compressed and loaded into the sheath with the use of a pusher catheter. The pusher catheter was held in place with one hand while the sheath was slowly withdrawn in a continuous motion with the other hand. This freed the stent and allowed it to lie within the stricture and expand. Just after the removal of the sheath and the pusher catheter, retrograde urethrography and voiding cystourethrography were performed to verify the position of the stent. Stent placement was technically successful and well tolerated in all patients.



View larger version (131K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3a. Patient 3. (a) Left anterior oblique retrograde urethrogram obtained before stent placement shows urethral stricture (arrow) near external sphincter (arrowheads). (b) Left anterior oblique radiograph obtained during stent placement shows placement of 9-F sheath (arrow) with dilator (arrowhead) over guide wire. (c) Left anterior oblique radiograph obtained during stent placement shows 9-F sheath containing compressed stent (arrows). (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows good flow of contrast medium through expanded stent (arrows). (e) Left anterior oblique radiograph obtained during stent removal shows sheath with dilator in stent lumen. (f) Left anterior oblique radiograph obtained during stent removal shows hook (arrow) in stent lumen. (g) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows partially collapsed portion (arrowheads) of stent. (h) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows completely collapsed portion (arrowheads) of stent. (i) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows improvement of stricture (arrow). (j) Left anterior oblique retrograde urethrogram obtained 6 months after stent removal shows slightly reduced lumen (arrow).

 


View larger version (136K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3b. Patient 3. (a) Left anterior oblique retrograde urethrogram obtained before stent placement shows urethral stricture (arrow) near external sphincter (arrowheads). (b) Left anterior oblique radiograph obtained during stent placement shows placement of 9-F sheath (arrow) with dilator (arrowhead) over guide wire. (c) Left anterior oblique radiograph obtained during stent placement shows 9-F sheath containing compressed stent (arrows). (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows good flow of contrast medium through expanded stent (arrows). (e) Left anterior oblique radiograph obtained during stent removal shows sheath with dilator in stent lumen. (f) Left anterior oblique radiograph obtained during stent removal shows hook (arrow) in stent lumen. (g) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows partially collapsed portion (arrowheads) of stent. (h) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows completely collapsed portion (arrowheads) of stent. (i) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows improvement of stricture (arrow). (j) Left anterior oblique retrograde urethrogram obtained 6 months after stent removal shows slightly reduced lumen (arrow).

 


View larger version (127K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3c. Patient 3. (a) Left anterior oblique retrograde urethrogram obtained before stent placement shows urethral stricture (arrow) near external sphincter (arrowheads). (b) Left anterior oblique radiograph obtained during stent placement shows placement of 9-F sheath (arrow) with dilator (arrowhead) over guide wire. (c) Left anterior oblique radiograph obtained during stent placement shows 9-F sheath containing compressed stent (arrows). (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows good flow of contrast medium through expanded stent (arrows). (e) Left anterior oblique radiograph obtained during stent removal shows sheath with dilator in stent lumen. (f) Left anterior oblique radiograph obtained during stent removal shows hook (arrow) in stent lumen. (g) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows partially collapsed portion (arrowheads) of stent. (h) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows completely collapsed portion (arrowheads) of stent. (i) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows improvement of stricture (arrow). (j) Left anterior oblique retrograde urethrogram obtained 6 months after stent removal shows slightly reduced lumen (arrow).

 


View larger version (112K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3d. Patient 3. (a) Left anterior oblique retrograde urethrogram obtained before stent placement shows urethral stricture (arrow) near external sphincter (arrowheads). (b) Left anterior oblique radiograph obtained during stent placement shows placement of 9-F sheath (arrow) with dilator (arrowhead) over guide wire. (c) Left anterior oblique radiograph obtained during stent placement shows 9-F sheath containing compressed stent (arrows). (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows good flow of contrast medium through expanded stent (arrows). (e) Left anterior oblique radiograph obtained during stent removal shows sheath with dilator in stent lumen. (f) Left anterior oblique radiograph obtained during stent removal shows hook (arrow) in stent lumen. (g) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows partially collapsed portion (arrowheads) of stent. (h) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows completely collapsed portion (arrowheads) of stent. (i) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows improvement of stricture (arrow). (j) Left anterior oblique retrograde urethrogram obtained 6 months after stent removal shows slightly reduced lumen (arrow).

 


View larger version (127K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3e. Patient 3. (a) Left anterior oblique retrograde urethrogram obtained before stent placement shows urethral stricture (arrow) near external sphincter (arrowheads). (b) Left anterior oblique radiograph obtained during stent placement shows placement of 9-F sheath (arrow) with dilator (arrowhead) over guide wire. (c) Left anterior oblique radiograph obtained during stent placement shows 9-F sheath containing compressed stent (arrows). (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows good flow of contrast medium through expanded stent (arrows). (e) Left anterior oblique radiograph obtained during stent removal shows sheath with dilator in stent lumen. (f) Left anterior oblique radiograph obtained during stent removal shows hook (arrow) in stent lumen. (g) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows partially collapsed portion (arrowheads) of stent. (h) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows completely collapsed portion (arrowheads) of stent. (i) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows improvement of stricture (arrow). (j) Left anterior oblique retrograde urethrogram obtained 6 months after stent removal shows slightly reduced lumen (arrow).

 


View larger version (121K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3f. Patient 3. (a) Left anterior oblique retrograde urethrogram obtained before stent placement shows urethral stricture (arrow) near external sphincter (arrowheads). (b) Left anterior oblique radiograph obtained during stent placement shows placement of 9-F sheath (arrow) with dilator (arrowhead) over guide wire. (c) Left anterior oblique radiograph obtained during stent placement shows 9-F sheath containing compressed stent (arrows). (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows good flow of contrast medium through expanded stent (arrows). (e) Left anterior oblique radiograph obtained during stent removal shows sheath with dilator in stent lumen. (f) Left anterior oblique radiograph obtained during stent removal shows hook (arrow) in stent lumen. (g) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows partially collapsed portion (arrowheads) of stent. (h) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows completely collapsed portion (arrowheads) of stent. (i) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows improvement of stricture (arrow). (j) Left anterior oblique retrograde urethrogram obtained 6 months after stent removal shows slightly reduced lumen (arrow).

 


View larger version (111K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3g. Patient 3. (a) Left anterior oblique retrograde urethrogram obtained before stent placement shows urethral stricture (arrow) near external sphincter (arrowheads). (b) Left anterior oblique radiograph obtained during stent placement shows placement of 9-F sheath (arrow) with dilator (arrowhead) over guide wire. (c) Left anterior oblique radiograph obtained during stent placement shows 9-F sheath containing compressed stent (arrows). (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows good flow of contrast medium through expanded stent (arrows). (e) Left anterior oblique radiograph obtained during stent removal shows sheath with dilator in stent lumen. (f) Left anterior oblique radiograph obtained during stent removal shows hook (arrow) in stent lumen. (g) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows partially collapsed portion (arrowheads) of stent. (h) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows completely collapsed portion (arrowheads) of stent. (i) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows improvement of stricture (arrow). (j) Left anterior oblique retrograde urethrogram obtained 6 months after stent removal shows slightly reduced lumen (arrow).

 


View larger version (111K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3h. Patient 3. (a) Left anterior oblique retrograde urethrogram obtained before stent placement shows urethral stricture (arrow) near external sphincter (arrowheads). (b) Left anterior oblique radiograph obtained during stent placement shows placement of 9-F sheath (arrow) with dilator (arrowhead) over guide wire. (c) Left anterior oblique radiograph obtained during stent placement shows 9-F sheath containing compressed stent (arrows). (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows good flow of contrast medium through expanded stent (arrows). (e) Left anterior oblique radiograph obtained during stent removal shows sheath with dilator in stent lumen. (f) Left anterior oblique radiograph obtained during stent removal shows hook (arrow) in stent lumen. (g) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows partially collapsed portion (arrowheads) of stent. (h) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows completely collapsed portion (arrowheads) of stent. (i) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows improvement of stricture (arrow). (j) Left anterior oblique retrograde urethrogram obtained 6 months after stent removal shows slightly reduced lumen (arrow).

 


View larger version (125K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3i. Patient 3. (a) Left anterior oblique retrograde urethrogram obtained before stent placement shows urethral stricture (arrow) near external sphincter (arrowheads). (b) Left anterior oblique radiograph obtained during stent placement shows placement of 9-F sheath (arrow) with dilator (arrowhead) over guide wire. (c) Left anterior oblique radiograph obtained during stent placement shows 9-F sheath containing compressed stent (arrows). (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows good flow of contrast medium through expanded stent (arrows). (e) Left anterior oblique radiograph obtained during stent removal shows sheath with dilator in stent lumen. (f) Left anterior oblique radiograph obtained during stent removal shows hook (arrow) in stent lumen. (g) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows partially collapsed portion (arrowheads) of stent. (h) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows completely collapsed portion (arrowheads) of stent. (i) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows improvement of stricture (arrow). (j) Left anterior oblique retrograde urethrogram obtained 6 months after stent removal shows slightly reduced lumen (arrow).

 


View larger version (124K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3j. Patient 3. (a) Left anterior oblique retrograde urethrogram obtained before stent placement shows urethral stricture (arrow) near external sphincter (arrowheads). (b) Left anterior oblique radiograph obtained during stent placement shows placement of 9-F sheath (arrow) with dilator (arrowhead) over guide wire. (c) Left anterior oblique radiograph obtained during stent placement shows 9-F sheath containing compressed stent (arrows). (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows good flow of contrast medium through expanded stent (arrows). (e) Left anterior oblique radiograph obtained during stent removal shows sheath with dilator in stent lumen. (f) Left anterior oblique radiograph obtained during stent removal shows hook (arrow) in stent lumen. (g) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows partially collapsed portion (arrowheads) of stent. (h) Left anterior oblique radiograph obtained while pulling hook (arrow) into sheath shows completely collapsed portion (arrowheads) of stent. (i) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows improvement of stricture (arrow). (j) Left anterior oblique retrograde urethrogram obtained 6 months after stent removal shows slightly reduced lumen (arrow).

 
Stent Removal Technique
In each patient, the first stent was electively removed by one author (H.Y.S.) 2 months after stent placement. In those patients with a recurrent stricture after stent removal, a second stent was placed and then removed 4 months later. After topical anesthesia of the urethra, a guide wire was introduced through the urethra across the stent into the prostatic urethra or the urinary bladder. A 9-F sheath with a dilator was passed over the guide wire into the proximal lumen of the stent. After the dilator was removed from the sheath, a hook wire was introduced into the sheath and was advanced until the hook was passed through the sheath into the lumen of the stent (Fig 3). Then the sheath with the hook was pulled out of the stent so that the hook caught onto the drawstring. When this happened, the hook wire was withdrawn through the sheath to collapse the stent. The sheath, stent, hook wire, and guide wire were pulled out of the urethra together. Two or three authors (H.Y.S., T.S.S., G.Y.K.) evaluated how the patient tolerated the removal procedure and also examined the removed stents.

Follow-up
In all patients, retrograde urethrography (T.S.S. or G.Y.K.), uroflowmetry, estimations of postvoiding residual urine volume, and urine cultures (H.P. or T.P.) were performed 1 week after stent placement and then every 4 weeks until the placed stent was removed. When the findings at urethrography showed full expansion of the stent, urethroscopy was performed by either one or two authors (H.P. or T.P.) to verify the patency of the stent. The patients were questioned by one of three authors (H.Y.S., H.P., T.P.) with regard to the frequency and urgency of micturition and concerning continence during the day and night. Clinical examinations, uroflowmetry, and retrograde urethrography were also performed 1 month, 3 months, and 12 months after the removal of the stent to assess recurrence. Thereafter, the patients were advised to visit an outpatient clinic when they had a recurrence of symptoms. All patients were contacted by telephone every 6 months until the end of the study.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
Stent Placement
All patients could void immediately after stent placement. They were continent in voiding. The mean maximum urine flow rate was 27 mL/sec (range, 16–40 mL/sec) at 1 week after stent placement. The stent was partially collapsed when the external urethral sphincter closed during retrograde urethrography and was fully dilated when the external urethral sphincter opened during voiding cystourethrography in all patients (Fig 4). Urethroscopy performed after the full expansion of the stent showed that the lumen of the stent remained widely open. For 1–7 days after the stent insertion procedure, all patients had mild urgency and discomfort at the site of stent placement; these two side effects disappeared spontaneously. After stent placement, six patients reported minor postmicturition dribbling, which disappeared spontaneously within 4 weeks. Formation of new strictures just above and below the stent occurred in two patients (patients 5 and 9). A luminal narrowing caused by hyperplastic tissue growth into the stent occurred in two patients (patients 1 and 11). In one patient who had infected urine before stent placement (patient 6), the urine was clear of microorganisms after 2 months of treatment with antibiotics.



View larger version (149K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 4a. Patient 5. (a) Left anterior oblique voiding cystourethrogram obtained before stent placement shows urethral stricture (arrow). (b) Left anterior oblique retrograde urethrogram obtained 3 days after stent placement shows partial collapse of stent (arrowheads) at external urethral sphincter. (c) Left anterior oblique voiding cystourethrogram obtained 3 days after stent placement shows expansion of stent at external urethral sphincter (arrowheads). Note urethral stricture (arrow) near external sphincter. (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows formation of new strictures (curved arrows) above and below stent. (e) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows new strictures (curved arrows) and improvement of original stricture (straight arrow), with irregularity at site of stent placement. (f) Left anterior oblique retrograde urethrogram obtained 1 month after stent removal shows improvement of irregularity and new strictures (curved arrows). Note slightly reduced lumen (straight arrow) of original stricture and external sphincter (arrowheads).

 


View larger version (125K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 4b. Patient 5. (a) Left anterior oblique voiding cystourethrogram obtained before stent placement shows urethral stricture (arrow). (b) Left anterior oblique retrograde urethrogram obtained 3 days after stent placement shows partial collapse of stent (arrowheads) at external urethral sphincter. (c) Left anterior oblique voiding cystourethrogram obtained 3 days after stent placement shows expansion of stent at external urethral sphincter (arrowheads). Note urethral stricture (arrow) near external sphincter. (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows formation of new strictures (curved arrows) above and below stent. (e) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows new strictures (curved arrows) and improvement of original stricture (straight arrow), with irregularity at site of stent placement. (f) Left anterior oblique retrograde urethrogram obtained 1 month after stent removal shows improvement of irregularity and new strictures (curved arrows). Note slightly reduced lumen (straight arrow) of original stricture and external sphincter (arrowheads).

 


View larger version (127K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 4c. Patient 5. (a) Left anterior oblique voiding cystourethrogram obtained before stent placement shows urethral stricture (arrow). (b) Left anterior oblique retrograde urethrogram obtained 3 days after stent placement shows partial collapse of stent (arrowheads) at external urethral sphincter. (c) Left anterior oblique voiding cystourethrogram obtained 3 days after stent placement shows expansion of stent at external urethral sphincter (arrowheads). Note urethral stricture (arrow) near external sphincter. (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows formation of new strictures (curved arrows) above and below stent. (e) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows new strictures (curved arrows) and improvement of original stricture (straight arrow), with irregularity at site of stent placement. (f) Left anterior oblique retrograde urethrogram obtained 1 month after stent removal shows improvement of irregularity and new strictures (curved arrows). Note slightly reduced lumen (straight arrow) of original stricture and external sphincter (arrowheads).

 


View larger version (131K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 4d. Patient 5. (a) Left anterior oblique voiding cystourethrogram obtained before stent placement shows urethral stricture (arrow). (b) Left anterior oblique retrograde urethrogram obtained 3 days after stent placement shows partial collapse of stent (arrowheads) at external urethral sphincter. (c) Left anterior oblique voiding cystourethrogram obtained 3 days after stent placement shows expansion of stent at external urethral sphincter (arrowheads). Note urethral stricture (arrow) near external sphincter. (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows formation of new strictures (curved arrows) above and below stent. (e) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows new strictures (curved arrows) and improvement of original stricture (straight arrow), with irregularity at site of stent placement. (f) Left anterior oblique retrograde urethrogram obtained 1 month after stent removal shows improvement of irregularity and new strictures (curved arrows). Note slightly reduced lumen (straight arrow) of original stricture and external sphincter (arrowheads).

 


View larger version (114K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 4e. Patient 5. (a) Left anterior oblique voiding cystourethrogram obtained before stent placement shows urethral stricture (arrow). (b) Left anterior oblique retrograde urethrogram obtained 3 days after stent placement shows partial collapse of stent (arrowheads) at external urethral sphincter. (c) Left anterior oblique voiding cystourethrogram obtained 3 days after stent placement shows expansion of stent at external urethral sphincter (arrowheads). Note urethral stricture (arrow) near external sphincter. (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows formation of new strictures (curved arrows) above and below stent. (e) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows new strictures (curved arrows) and improvement of original stricture (straight arrow), with irregularity at site of stent placement. (f) Left anterior oblique retrograde urethrogram obtained 1 month after stent removal shows improvement of irregularity and new strictures (curved arrows). Note slightly reduced lumen (straight arrow) of original stricture and external sphincter (arrowheads).

 


View larger version (130K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 4f. Patient 5. (a) Left anterior oblique voiding cystourethrogram obtained before stent placement shows urethral stricture (arrow). (b) Left anterior oblique retrograde urethrogram obtained 3 days after stent placement shows partial collapse of stent (arrowheads) at external urethral sphincter. (c) Left anterior oblique voiding cystourethrogram obtained 3 days after stent placement shows expansion of stent at external urethral sphincter (arrowheads). Note urethral stricture (arrow) near external sphincter. (d) Left anterior oblique retrograde urethrogram obtained 2 months after stent placement shows formation of new strictures (curved arrows) above and below stent. (e) Left anterior oblique retrograde urethrogram obtained immediately after stent removal shows new strictures (curved arrows) and improvement of original stricture (straight arrow), with irregularity at site of stent placement. (f) Left anterior oblique retrograde urethrogram obtained 1 month after stent removal shows improvement of irregularity and new strictures (curved arrows). Note slightly reduced lumen (straight arrow) of original stricture and external sphincter (arrowheads).

 
Stent Removal
The first stent was removed from all patients 2 months after stent placement. Removal of the stent was well tolerated in all but three patients (patients 1, 5, and 11). Urethrograms obtained immediately after removal of the stent showed improvement of the stricture, with irregularity at the site of stent placement (Fig 3).

In patient 5, who had formation of new strictures above and below the stent, the drawstring became untied during the removal of the stent. To remove the stent, we introduced the hook wire proximal to the stent and hooked the proximal end of the wire mesh. The stent was retrieved with eversion.

In patients 1 and 11, who had luminal narrowing caused by hyperplastic tissue growth, the stent was so reluctant to be pulled out of the stricture that the drawstring became untied during the removal of the stent. To remove the stent, we tightly pulled the drawstrings into the sheath while the sheath was being pushed over the stent. Then we rotated the sheath with the hook to twist the distal end of the stent in the urethral lumen. Hyperplastic tissue was between the polyurethane membrane and the wire mesh. The tissue pushed the membrane into the lumen of the stent. There was no hole in the membrane. The tissue ingrowth made the removal difficult.

Nine of 22 removed stents were bloodstained. In the patients with the bloodstained stents, a small amount of hematuria occurred after the stent was removed, but bleeding stopped spontaneously within 20 minutes of removal.

Follow-up
The patients were followed up for a mean of 20 months (range, 2–37 months) after the removal of the first stent (Table). The initial improvement rate was 100%, but strictures recurred in eight of the 12 patients at 3–8 weeks (mean, 4 weeks) after stent removal. For these eight patients, a second stent was placed and then removed from seven of the eight patients 4 months later. During the mean follow-up of 18 months (range, 4–32 months) after the removal of the second stent, five of the seven patients did not need further treatment because of the improvement of the stricture. Strictures recurred in two (patients 6 and 10) of the seven patients at 4 weeks after the removal of the second stent. For those two patients, a third stent was placed and then removed 4 months later, with a good result. Four (33%) of 12 patients, five (62%) of eight patients, and two (100%) of two patients were successfully treated with placement of the first stent, the second stent, and the third stent, respectively. In the remaining patient, the second stent remains in place.


View this table:
[in this window]
[in a new window]

  		Urethral Stent Placement in 12 Patients

 
Eleven of 12 patients were followed up for a mean of 18 months (range, 4–32 months) after the removal of the last stent. They are free of symptoms as of the time of this writing. The mean maximum urine flow rate was 25 mL/sec (range, 18–43 mL/sec) at 3 months after removal of the last stent. The follow-up urethrograms showed patency of the lumen, with a slightly reduced but satisfactory lumen in comparison with the urethrograms obtained immediately after removal of the last stent (Fig 3).


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES
 
The ideal outcome of treatment of bulbomembranous urethral strictures should be the preservation of continence and the elimination of the obstruction (2). The results of our study indicate that the placement of a covered, retrievable, expandable nitinol stent seems to be effective in the treatment of urethral strictures near the external sphincter because the stent keeps the urethral strictures near the external sphincter open without disturbing the function of the external sphincter mechanism. The stent was able to dilate the strictures as much as the diameter of the stent because the placed stent tended to exert an expansile force until it reached the preset expanded diameter. While in place, the stent showed its partial contraction and full expansion in accordance with the function of the external urethral sphincter. After the removal of the stent, the external urethral sphincter maintained its function. We surmise that the stent was rigid enough to dilate the stricture but soft enough not to damage the external urethral sphincter.

Two different types of metallic stents, permanent metallic stents (1,6–14) and temporary metallic stents (2,3,15,16), have been used in the minimally invasive treatment of recurrent bulbomembranous urethral strictures. However, in previous studies (3,7,8,10,11) that have included more than 18 and fewer than 175 patients with a recurrent urethral stricture, the rate of late complications, such as a luminal narrowing caused by hyperplastic tissue growth, erectile disorders, encrustation, stent migration, and incontinence, was as high as 39%–47%. The luminal narrowing caused by hyperplastic tissue growth occurred in 50% of the traumatic urethral strictures and posturethroplasty strictures. In addition, once epithelium has completely covered the stent, it is not possible to remove the stent from patients who have strictures without performing surgery (9). Therefore, Milroy and colleagues (6,9,12) have determined that bulbomembranous urethral strictures that occur after traumatic urethral rupture or failed urethroplasty are not suitable for permanent stents.

Temporary stents have an obvious advantage, compared with permanent stents, in that no foreign material is left in the urethra (4). Yachia and Beyar (2) used a temporary metallic coil stent in 20 patients. In 13 of the 20 patients, the stent was left in place for 10 months and was then removed with a simple manipulation. After a mean follow-up of 10 months (range, 3–14 months), the stricture recurred in only one patient. Sikafi (3) placed a coil stent in 18 patients with recurrent urethral strictures. Migration of the coil stent occurred in three (17%) of the 18 patients, encrustations in two patients, hyperplasia distal to the stent in two patients, urinary tract infection in three patients, and discomfort during erection in four patients.

The coil stent is a tightly closed coil that has a wavy form and an alternating caliber of 26–32 F. Because of its tightly closed loops, it does not become embodied in the urethral wall and can be removed after periods as long as 12 months (2). The coil stent for use in strictures near the external sphincter has three parts: (a) the prostatic part, which is 10 mm long; (b) the bulbomembranous part, which has a length of 30–70 mm after expansion; and (c) the 20-mm transsphincteric part, which is a single helical wire connecting the first two parts. Although the coil stent was retrievable, a rigid endoscopic forceps and a 12-F Foley catheter were needed to remove the stent. In addition, the coil stent does not seem to be suitable for the treatment of urethral strictures within or near the external sphincter because the 20-mm transsphincteric part could not open the stricture.

To solve the problems associated with the permanent and temporary metallic stents, Isotalo and colleagues (4) used a bioabsorbable, self-reinforced, poly-L-lactic acid double spiral stent in 22 patients with recurrent urethral strictures. The stent had degraded in all patients at 12 months. A positive feature was that there was no need to remove the stent, and no foreign material remained in the urethra because the end products of the degradation were water and carbon dioxide, with no toxic properties. However, the hardness of the stent decreased during the healing process. Ten (45%) of the 22 patients showed recurrence—outside the stent area in seven patients and in the stent area in three. Moreover, to our knowledge, the bioabsorbable stents have never been used in the treatment of urethral strictures within or near the external sphincter.

In our series of 12 patients with urethral strictures, the recurrence rate during the mean follow-up of 20 months after removal of the first stent at 2 months was 67% (eight of 12 patients). In the eight patients with recurrence, a second stent was placed and then removed from seven of the eight patients 4 months after placement, with recurrence in two patients. With regard to the optimal time for the removal of placed stents, we agree that urethral stents should remain in place until complete tissue healing occurs in the surrounding urethra (2). We also agree that the optimal time for removal will be different in each case, depending on the causes, length, duration, and severity of the strictures. Yachia and Beyar (2) suggested 8–12 months as an optimal period. In the case of partial fibrosis, 6 months was suggested as the optimal time for removal of a urethral stent because it seemed to be enough time to allow for complete tissue healing (16). Although we believe that the optimal time for urethral stent removal is still undetermined, it is now our policy to remove the stent 4 months after placement, not only because hyperplasia proximal or distal to the stent was not common within that period, but also because recurrence of the strictures was not common during that period.

Two of our 12 patients had formation of new strictures above and below the placed stent. The new strictures improved after stent removal in the two patients. Parikh and Milroy (12) suggest that the formation of a new stricture at one or the other end of the stent is probably a reaction to the stent itself. Although it may be noted on urethrograms and at urethroscopy, a new stricture rarely causes any important narrowing of the urethra. However, when this stent has been used in other parts of the body, some investigators have proposed that unless the stent is removed, the formation of a new stricture in the tracheobronchial tree (17) and in the esophagus (18) eventually causes the recurrence of symptoms and necessitates further treatment. In all patients with new strictures, the new stricture improved during the follow-up period after stent removal (18).

Ko and colleagues (19) placed a covered retrievable nitinol stent in the posterior urethra of 20 male mongrel dogs. Mild to severe hyperplastic tissue growth above or below the stent occurred in 17 dogs. These investigators removed the stent from 10 dogs at 4 weeks after placement and from the other 10 dogs at 8 weeks after placement. They reported that urethrograms and the results of histologic examinations obtained 2 weeks after removal of the stent revealed that the tissue growth had almost normalized.

The polyurethane-covered, retrievable, expandable nitinol stent can be removed either when it causes complications or when tissue healing occurs in the surrounding urethra. We believe that use of a retrievable stent can extend the indications for stent placement to patients with a urethral stricture near the external sphincter, whose lesions were previously considered difficult to treat. The covered stent, however, should be well attached to the wire mesh so as not to allow tissue growth between the wire mesh and the polyurethane membrane, as happened in two patients in the current study. In conclusion, although further clinical trials are needed, our preliminary results indicate that the placement of a covered, retrievable, expandable nitinol stent seems to be feasible in the treatment of urethral strictures near the external sphincter and warrants further investigation.


   FOOTNOTES
 
Author contributions: Guarantor of integrity of entire study, H.Y.S.; study concepts, H.Y.S., H.P.; study design, H.Y.S., H.P., T.P.; literature research, T.S.S., G.Y.K.; clinical studies, H.Y.S., H.P., G.Y.K., T.P.; data acquisition, E.S.K., T.H.K.; data analysis/interpretation, H.Y.S., H.P., T.H.K.; manuscript preparation, H.Y.S.; manuscript definition of intellectual content, H.P., T.P.; manuscript editing, H.Y.S., H.P., G.Y.K.; manuscript revision/review, T.P., T.S.S.; manuscript final version approval, H.Y.S.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 

  1. Milroy EJG, Chapple CR, Cooper JE, Eldin A, Wallsten H, Seddon AM. A new treatment for urethral strictures. Lancet 1988; 1:1424-1427.[Medline]
  2. Yachia D, Beyar M. New, self-expanding, self-retaining temporary coil stent for recurrent urethral strictures near the external sphincter. Br J Urol 1993; 71:317-321.[Medline]
  3. Sikafi ZH. A self-expanding, self-retaining temporary urethral stent (UrocoilTM) in the treatment of recurrent urethral strictures: preliminary results. Br J Urol 1996; 77:701-704.[Medline]
  4. Isotalo T, Tammela TLJ, Talja M, Välimaa T, Törmälä P. A bioabsorbable self-expandable, self-reinforced poly-l-lactic acid urethral stent for recurrent urethral strictures: a preliminary report. J Urol 1998; 160:2033-2036.[CrossRef][Medline]
  5. Niesel T, Moore RG, Alfert HJ, Kavoussi LR. Alternative endoscopic management in the treatment of urethral strictures. J Endourol 1995; 9:31-39.[Medline]
  6. Milroy EJG, Allen A. Long-term results of Urolume stent for recurrent urethral strictures. J Urol 1996; 155:904-908.[CrossRef][Medline]
  7. Badlani GH, Press SM, Defalco A, Oesterling JE, Smith AD. Urolume endourethral prosthesis for the treatment of urethral stricture disease: long-term results of the North American Multicenter UroLume Trial. Urology 1995; 45:846-856.[CrossRef][Medline]
  8. Guzman Martinez-Valls PL, Ferrero Doria R, Tomas Ros M, et al. Endourethral prosthesis in recurrent urethral stenosis: long-term follow-up. Arch Esp Urol 1996; 49:421-425[Spanish].[Medline]
  9. Milroy EJG. Treatment of sphincter strictures using permanent Urolume stent. J Urol 1993; 150:1729-1733.[Medline]
  10. Tillem SM, Press SM, Badlani GH. Use of multiple Urolume endourethral prostheses in complex bulbar urethral strictures. J Urol 1997; 157:1665-1668.[CrossRef][Medline]
  11. Corujo M, Badlani GH. Uncommon complications of permanent stents. J Endourol 1998; 12:385-388.[Medline]
  12. Parikh AM, Milroy EJG. Precautions and complications in the use of the Urolume Wallstent. Eur Urol 1995; 27:1-7.
  13. Baert L, Verhamme L, Van Poppel H, Vandeursen H, Baert J. Long-term consequences of urethral stents. J Urol 1993; 150:853-855.[Medline]
  14. Donald JJ, Rickards D, Milroy EJG. Stricture disease: radiology of urethral stents. Radiology 1991; 180:447-450.[Abstract/Free Full Text]
  15. Yachia D, Lask D, Rabinson S. Self-retaining intraurethral stent: an alternative to long-term indwelling catheters or surgery in the treatment of prostatism. AJR Am J Roentgenol 1990; 154:111-113.[Abstract/Free Full Text]
  16. Yachia D, Beyar M. New treatment modality for penile urethral strictures using a self-expanding and self-retaining coil stent: UroCoil—follow-up of 16 months after removal of the stent. Eur Urol 1993; 24:500-504.[Medline]
  17. Song HY, Shim TS, Kang SG, et al. Tracheobronchial strictures: treatment with a polyurethane-covered retrievable expandable nitinol stent—initial experience. Radiology 1999; 213:905-912.[Abstract/Free Full Text]
  18. Song HY, Jung HY, Park SI, et al. Covered retrievable expandable nitinol stents in patients with benign esophageal strictures: initial experience. Radiology 2000; 217:551-557.[Abstract/Free Full Text]
  19. Ko GY, Kim GC, Seo TS, et al. Covered, retrievable, expandable urethral nitinol stent: feasibility study in dogs. Radiology 2002; 223:83-90.[Abstract/Free Full Text]



This article has been cited by other articles:


Home page
 Am. J. Roentgenol.Home page
E. K. Choi, H.-Y. Song, J. H. Shin, J.-O. Lim, H. Park, and C.-S. Kim
Management of Recurrent Urethral Strictures with Covered Retrievable Expandable Nitinol Stents: Long-Term Results
Am. J. Roentgenol., December 1, 2007; 189(6): 1517 - 1522.
[Abstract] [Full Text] [PDF]

Home page
 RadiologyHome page
J. H. Shin, H.-Y. Song, C. G. Choi, S. H. Yuk, J.-S. Kim, Y. M. Kim, C. J. Yoon, T.-H. Kim, J.-Y. Suh, and X. He
Tissue Hyperplasia: Influence of a Paclitaxel-eluting Covered Stent--Preliminary Study in a Canine Urethral Model
Radiology, February 1, 2005; 234(2): 438 - 444.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
2262012160v1
226/2/433    most recent
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Song, H.-Y.
Right arrow Articles by Park, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Song, H.-Y.
Right arrow Articles by Park, T.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
RADIOLOGY RADIOGRAPHICS RSNA JOURNALS ONLINE