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USE OF SELF-EXPANDING PERMANENT ENDOLUMINAL STENTS FOR BENIGN URETERAL STRICTURES: MID-TERM RESULTS
0022-5347/99/1622-031910 THEJOURNAL OF UROLOGY Copyright 0 1999 by AMERICAN UROLOGICAL ASSOCIATION, INC.
Vol. 1 6 2 , 3 1 9 4 2 2 , August 1999 Printed in U.S.A.
USE OF SELF-EXPANDING PERMANENT ENDOLUMINAL STENTS FOR BENIGN URETERAL STRICTURES: MID-TERM RESULTS WALTER PAUER
AND
GUDRUN M. ECKERSTORFER
From the Department of Urology, General Hospital Wels, Wels, Austria
ABSTRACT
Purpose: Benign ureteral strictures constitute a therapeutic dilemma, especially in patients unable to undergo an open operative procedure. We report on 13 patients with benign ureteral strictures treated with endoscopic implantation of self-expanding permanent endoluminal stents. Materials and Methods: Endoscopic implantation was done using the Wallstent" in 4 patients, the Memothermi- stent in 5 and the Sinus$ stent in 4. The technique of implantation followed the standardized procedure that we described in 1995. Results: Mean followup was 41.6 months. Primary patency (ureters patent since implantation) was achieved in 7 patients and assisted patency (additional intervention) was noted in 5. In 1 case the kidney had to be removed because of progressive malfunction. Conclusions: Implantation of self-expanding permanent endoluminal stents for benign ureteral strictures is safe, effective and minimally invasive in select cases. Additional studies and long-term results are needed to make definitive conclusions about this method. KEYWORDS:ureter, stents Since Milroy described the first application of a selfexpanding permanent endoluminal stent in the urethra in 1988,l the next logical step was to use these stents in the ureter. New and modified techniques of implantation were developed t o account for the different anatomical and functional system.' The first application of a self-expanding permanent endoluminal stent in the ureter was reported by Gort et a1 in 1990, who used a Wallstent for a ureteroileal anastomotic stricture. Since then these stents have been used successfully by others for treatment of extrinsic malignant and benign ureteral strictures. Complicated ureteral strictures often lead to permanent urinary diversion or loss of the kidney. Encouraged by our results in malignant extrinsic ureteral obstructi~n,~." we used self-expanding permanent Accepted for publication February 26, 1999 Schneider, Switzerland. NovoMed Inc., Mannheim, Germany. 7 Optimed, Germany,
7
@ :
endoluminal stents in otherwise untreatable patients with benign ureteral strictures. MATERIALS AND METHODS
From March 1994 to May 1998 a self-expanding permanent endoluminal stent was implanted in 13 patients, including 2 with a solitary kidney, in the manner developed and described by us previously.' Mean patient age was 56.8 years and mean followup was 41.6 months (table 1).Implantation was done using the Wallstent, a cobalt chromium nickel molybdenum iron alloy, in 4 patients and the Memotherm or Sinus stent, a nickel titanium alloy, in 9. All patients had scarred ureteral strictures caused by preexisting diseases or interventions (table l),and were unable to undergo open surgery for cardiac or other reasons, or did not want to undergo reoperation. Previous treatments were insufficient or did not meet patient expectations.
TABLE1 Pt. No.
Stricture Length - Sex
-Age
Implantation Side Date
Location
Stent
(cm.) 2-5
Preexisting Disease
Previous
or Intervention
Wallstent
Aortofemoral bypass
1 - F - 52.8
3/4/94
Rt.
Mid ureter
2 - F -55.5 3 - F - 74.8 4 - F - 52.2
3/4/94 5/26/94 6/7/94
Lt. Lt. Rt.
Mid ureter Mid ureter Distal ureter
Greater than 5 2-5 2-5
5 - F -662.7 6 - F -41.4 7 - F -37.9
9/30/94 10/27/94 3/31/95
Rt. Lt. Lt.
Mid ureter Distal ureter Distal ureter
Greater than 5 2-5 2-5
Radiation Crohn's disease Repeated ureteroscopy Mernotherm Radiation Memotherm Bowel surgery Gynecological surgery Wallstent
8-
F -53.8
9/23/96
Lt.
Distal ureter
Greater than 5
Memotherm
91011-
F -64.9 F -83.3 F -73.5
3/7/97 7/16/97 10/1/97
Lt. Rt. Lt.
Mid ureter Mid ureter Distal ureter
Greater than 5 2-5 2-5
Sinus Memotherm Sinus
12-
M -28.3
4/1/98
Rt.
Mid ureter
2-5
Sinus
13-
F -49.1
5/7/98
Lt.
Mid ureter
2-5
Sinus
Wallstent Wallstent Memothe rm
* Nephrectomy was performed after 46.5 months. 319
Percutaneous nephrostomy Double-J Double-J Double-J
Ureterolysis Ureterolysis Percutaneous nephrostorny Gynecological surgery Ureter reimplantation Radiation Double-J Aortofernoral bypass Double-J Urogenital Percutaneous tuberculosis nephrostomy Bilharziasis Ureter reimplantation Retroperitoneal Ureterolysis fibrosis
Primary Patency (mos.)
Assisted Patency (mos.)
54.4 54.43 51.6 51.27 47.4 41.3 23.3 17.8 13.4 10.8 4.8 3.6
320
PERMANENT ENDOLUMINAL STENTS FOR BENIGN URETERAL STRICTURES
FIG. 2. Endoscopic view of stented ureter. Entire foreground represents stent area covered by fine lining of urothelium without edema or hyperplasia. Small part of normal, unstented ureter is seen in background.
TABLE2. Assisted patency No. Pts. 2 2 1
FIG. 1. One year aRer stent im lantation urography reveals normal nondilated upper tract on rig& side. Stent area is marked with 2 arrows. "he technique of implantation followed a standardized procedure.* "he stricture is localized by fluoroscopy, the length of the stricture is determined and an adequate stent is selected. A soft tip guide wire is inserted via a ureteral catheter and the stricture is bypassed with the guide wire. After removal of the ureteral catheter a balloon dilation catheter is inserted over the guide wire and the balloon is located inside the stricture area. The stricture is dilated to a minimum of 5 mm. in diameter, with pressure as needed which sometimes reaches 17 atm. It is important to dilate the stricture adequately to avoid hourglass shape deformation of the stent. After dilation the balloon catheter is replaced by the stent catheter and the stent is released with care. It is advisable to choose a stent which exceeds the stricture at least 5 mm. on both ends to avoid overgrowth and re-obstruction at the ends. Finally, we implant a Double-J* catheter for 4 to 6 weeks to bridge the initial urothelial hyperplasia. To avoid kinking of the ureter in the prevesical area it is important to locate the distal end of the stent inside the intramural part of the ureter, just behind the orifice, thus preventing reflux. Followup was a mean of 41.6 months (range 7 to 55), and included ultrasonography, urography (fig. 1) and scintigraphy with furosemide washout. Ureteroscopy was done only when needed (fig. 2).
Problem
of scar tissue into the lumen of the stent. I n 1patient 2 years after endoscopic removal of the stricture a calculus developed which was too big to pass the stent area of the ureter, and had to be disintegrated and removed endoscopically. Ureteroscopy of the stent area was uneventful and showed normal urothelium. In 2 patients incrustation of a small part of the stent not covered by urothelium developed due to bad apposition to the ureteral wall and was removed endoscopically. Stone analysis revealed a uric acid stone in 1 patient who was given medication. In 1patient obstruction persisted after removal of the Double-J catheter due to incorrect stent placement and another overlapping stent on the proximal end of the stricture was implanted. In 1patient kidney function was only 5% of the overall function of both kidneys at stent implantation and subsequently deteriorated further, and so the kidney had to be removed. The indication to implant a stent in this case was wrong and we consider this a failure. No infection, migration or alteration of other organs was observed. DISCUSSION
Ureteral obstruction constitutes a therapeutic dilemma. Double-J stents, balloon dilation and endoscopic incision do not provide satisfactory results according t o the literature.6-8 However, it is desirable to spare patients the discomfort of a permanent nephrostomy tube or frequent exchange of Double-J catheters. In general, strictures greater than 2 cm., ischemic or in the mid ureter do not respond well to standard endoscopic techniques, such as balloon dilation or incision or ureteral cutting balloon catheter incision. Bal-
RESULTS
Primary patency was achieved in 7 patients with the ureters patent from implantation to date, assisted patency, that is patency achieved with secondary intervention, was achieved in 5 (table 2) and implantation was considered a failure in 1.In 2 patients a stricture recurred due to ingrowth * Medical Engineering Corp., New York, New York.
Treatment
Recurrent stricture Laser ablation inside stent Incrustation Endoscopic removal Misplacement of stent Overlapping implantation of another stent
TABLE 3 %
References
Intervention
Patency
Clayman and Kavoussi'
Balloon dilation Endoscopic-incision (cold knife) Acucise incision Self-expanding permanent endoluminal stent
55 79 73 69.1
Cohen et a18 Various studies from literature
PERMANENT ENDOLUMINAL STENTS FOR BENIGN URETERAL STRICTURES
321
TABLE4 References
No,
FYloyp
No. Patencyl Total No. ll1 444 ll1
Stent/Diameter bun.)
art et a13 Daniels et a19 Sanders et allo
1 4 1
6 9(mean) 7
Newman et all' Reinberg et allz
11 5
3-2 1 6-13
4/11 515
Wallstent /10,8 Wallstent /lo, 8
Noble et all3 Rickards'* Pollack et all'
5 7 6
6-12 6-12 ll(mean)
515 6/7 ll6
Wallstent 16 Wallstent /7 Wallstent /10
Herrero et all6
2
36
2/2
Wallstent /6
Masulovic et al" Lock et a1" Burgos et all9
18 16$ 9
12(mean) 6-90 3-19
8/19 10/16 10/12
Streckert/6,8 Wallstent /7 Memotherm / 4 , 8
Pauer and Lugmay?'
11
7-55
12/13
Wallstent /7 Memothem /8 sinus /7
Wallstent 16 Wallstent /? Palmaz*/?
Conclusions May salvage failed balloon dilation of benign strictures May be useful in seleeted patients with ureterointestinal stricture Can be successful, no success predictors identified Adequate alternative treatment, clinical experience and histology are encouraging Should be considered for post-radiation strictures Role for this method, pt. selection is crucial Wallstents are ineffective in benign ureteroenteric strictures Useful technique in management of strictures aRer kidney transplantation Signiscant better effect than interventional procedures An attractive alternative with good and long lasting results Safe and effective method, further long-term followup is needed Safe and effective, further experimental research and long-term experience are needed
95 3-90 67/97 (69.1) Overall (%) *Johnson & Johnson. Intervention Svstems. Warren. New Jersev. t Boston Scientific Co'rp.,Watertown,- Massachusetts.' $ Including case of Gort et al.3
loon dilation and ureterotomy remain reasonable options for benign ureteral strictures less than 2 cm. Ureterotomy has a higher success rate but requires more expertise and has a higher complication rate. Extreme caution should be exercised when incising strictures in the vicinity of major vessels, especially the iliac vessels. Although patency rates are higher for ureterotomy than self-expanding permanent endoluminal stents, the complication rates for the stents are significantly10wer.~*~ Patency rates of self-expandingpermanent endoluminal stents far exceed balloon dilation and nearly equal the Acucise* procedure (table 3). Several groups have treated benign ureteral strictures with the Wallstent or nitinol stents. A total of 97 cases of benign ureteral strictures were reported with followup beand - ~ the ~ overall success rate tween 3 and 90 m o n t h ~ , 3 . ~ was 69.1% (67 of 97 cases). Positive conclusionswere made in 11of the 12 studies and only 115indicated that this method was ineffective (table 4). Urothelial hyperplasia was described in most cases as the main cause of re-obstruction. However, a metal stent at least provides a buttress for the previously obstructed segment of the ureter, and so the lumen, although decreased by hyperplasia, is held open, which allows eventually an easy exchange of a Double-J stent, which then can provide patency. Urothelial hyperplasia, a main problem of self-expandhg permanent endoluminal stents, eventually can be minimized using biocompatible polymer lined stents.'* Animal experiments with these stents indicated a significant increased patency in ureters treated with lined versus bare stents. Moderate to severe hydroureteronephrosis and significant urothelial hyperplasia with ingrowth through the spaces between the metal wires developed in all animals with bare metal stents, which confirms the results in other animal experiments done in 1995F2Of the animals implanted with lined stents 1 had mild hydroureteronephrosis and there were no papillary ingrowths of urothelium through the stent interstices. This obstructive phenomenon was prevented by the porous polymer lining grossly and histolo~calb'. Different conclusions can be drawn f?om clinical results in humans. Re-obstruction by urothelial hyperplasia is a common problem which does not necessarily occur in dl patients, nor is it a persistent phenomenon. To our knowledge the only description ofa histological specimen of a removed but patent self-expanding permanent endoluminal stent W= r e p o d by Reinberg et d.12Stent material or design obviously does * Applied Medical Resources, Laguna Hills, California.
not have any effect on the outcome of the relief of obstruction, although hydrodynamic considerations suggest a conical shape (angulation 3 to 4 degrees) to minimize outflow resistance at the distal end of the self-expanding permanent endoluminal stent. Stent diameter, however, needs to be considered as re-obstruction by hyperplasia can probably occur more easily with small diameters. A diameter of 7 mm. is recommended to enable later endoscopic procedures. In conclusion, with careful patient selection implantation of selfexpanding permanent endoluminal stents seems safe and effective for otherwise untreatable patients with benign ureteral strictures. Further clinical experience with long-term results and experimental studies are needed. REFERENCES
1. Milroy, E. J. G., Chapple, C. R., Cooper, J. E., Eldin, A., Wallsten, H., Seddon, A. M. and Rowles, P. M.: A new treatment for urethral strictures. Lancet, 1: 1424, 1988. 2. Pauer, W. and Kerbl, K.: Self-expanding permanent endoluminal stents in the ureter: technical considerations.Tech. Urol., 1: 67, 1995. 3. Gort, H.B., Mali, W. P., van Waes, P. F. and Kloet, A. G.: Metallic self-expandable stenting of a ureteroileal stricture (Letter to the Editor). AJR, 165: 422,1990. 4. Pauer, W. and Lugmayr, H.: Metallic Wallstents: A new therapy for extrinsic ureteral obstruction.J. Urol., 148. 281, 1992. 5. Lugmayr, H. and Pauer, W.: Self-expanding metal stents for palliative treatment of malignant ureteral obstruction. AJR, 169 1091, 1992. 6. Docimo, S.G. and Dewolf, W. C.: High failure rate of indwelling ureteral stents in patients with extrinsic obstruction: experience at 2 institutions. J. Urol., 142: 277, 1989. 7. Clayman, R. V. and Kavoussi, L. R.: Endosurgical techniques for the diagnosis and treatment of noncaldous disease of the ureter and kidney. In: Campbell's Urology, 6th edition. Edited by P. C. Walsh, A. B. Retik, T. A. Stamey and E. D. Vaughn, Jr. Philadelphia: W. B. Saunders, vol. 12, chapt. 62, p. 2231-2312,1992. 8. Cohen, T. D., Gross, M. B. and Preminger, G. M.: Long-term follow-up of Acucise incision of ureteropelvic junction obstruction and ureteral strictures. Urology, 47: 317,1996. 9. Daniels, G. F.,Dake, M. D., Wexler, L., Signer, B. and Wittich, G.:R.:Use of metal stentsfor treatment of benign ureteral and ureteroenteric strictures. Suppl. Rad., 1% 230, 1992. 10. Sanders, R.,Bissada, N. K. and Bielsky, S.:Ureteroentericanastomotic strictures: Treatment with Palmaz permanent indwelling stents: J. Urol., 1M):469, 1993. 11. Newman, R., Moody, D. and Cohen, M.: Wallstents for ureteral strictures-do they work? J. Endouml.. 8: 112,1994. 12. Reinberg,Y.,Ferral, H.,Gonzalez, R., Manivel, J. C., Hulbert, J..
322
PERMANENT ENDOLUMINAL STENTS FOR BENIGN URETERAL STRICTURES
metal stent regarding the treatment of stricture of ureteroMaynar, M., Pulido-Duque, J. M., Hunter, D. and intestinal anastomosis. Brit. J. Urol., suppl. 2A, 80:348,1997. Castaneda-Zuniga, W. R.: Intraureteral metallic selfexpanding endoprosthesis (Walktent) in the treatment of dif- 18. Lock, T. M. T. W., van Waes, P. F. G. M., van Schaik, J. P. J., Zeijlemaker, B. Y. W. and Boon, T. A.: Endourological treatficult ureteral strictures. J. Urol., 151: 1619, 1994. ment of strictured ureteroileal (UI) anastomoses using a self13. Noble, J. G., Milroy, E. J. G. and Rickards, D.: The use of expandable permanent metallic stent (Wallstent). J. Urol., permanent metal stents in ureteric stricture disease. BAUS, abstract 88,1994. part 2, 151: 126,abstract 492,1997. 14. Rickards, D.: Permanent metal stents for the treatment of ure- 19. Burgos, J., G6mez, V., Carrera, C., Llorente, T., Pascual, J., Escudero, A.: Self-expanding metal stents for treatment of teric strictures. First International Workshop on Interventional Radiology, Prague, abstract 65,1994. ureteral obstruction. Eur. Urol., suppl 1, 33: A453, 1998. 15. Pollack, J.S.,Rosenblatt, M. M., Egglin, T. K., Dickey, K. W. and 20. Pauer, W. and Lugmayr, H.: Use of selfexpanding permanent endoluminal stents (SPES) in benign ureteral strictures. MidGlickman, M.: Treatment of ureteral obstructions with the Wallstent endoprosthesis: preliminary results. J. Vasc. Interv. term Results. J. Urol., part 2, 159 319,abstract 1224, 1998. Rad., 6 417, 1995. 21. Leveillec, R.J.,Pinchuk, L., Block, N. L. and Wilson, G. J.: A new self-expanding lined stent in the dog ureter: radiological, 16. Herrero, J. A,, Lezana, A., Gallego, J., Maraiies, A,, Prats, D., gross, histopathological and scanning electron microscopic Portoles, J., Torrente, J. and Bamentos, A.: Self-expanding findings. J. Urol., part 2, 159 318,abstract 1221,1998. metallic stent in the treatment of ureteral obstruction after renal transplantation. Nephrol. Dial. Transplant., 11: 887, 22. Desgrandchamps, F., Tuchschmid, Y., Cochand-Priollet, B., 1996. Therin, M., Teillac, P. and LeDuc, A.: Experimental study of 17. Masulovic, D., Markovic, Z., Goldner, B., Bozovic, Z., Djokic, Wallstent self-expandable metal stent in ureteral implantaJ. H. and Maletic, V.: Long-term effects in the application of tion. J. Endourol. 9 477,1995
Vol. 1 6 2 , 3 1 9 4 2 2 , August 1999 Printed in U.S.A.
USE OF SELF-EXPANDING PERMANENT ENDOLUMINAL STENTS FOR BENIGN URETERAL STRICTURES: MID-TERM RESULTS WALTER PAUER
AND
GUDRUN M. ECKERSTORFER
From the Department of Urology, General Hospital Wels, Wels, Austria
ABSTRACT
Purpose: Benign ureteral strictures constitute a therapeutic dilemma, especially in patients unable to undergo an open operative procedure. We report on 13 patients with benign ureteral strictures treated with endoscopic implantation of self-expanding permanent endoluminal stents. Materials and Methods: Endoscopic implantation was done using the Wallstent" in 4 patients, the Memothermi- stent in 5 and the Sinus$ stent in 4. The technique of implantation followed the standardized procedure that we described in 1995. Results: Mean followup was 41.6 months. Primary patency (ureters patent since implantation) was achieved in 7 patients and assisted patency (additional intervention) was noted in 5. In 1 case the kidney had to be removed because of progressive malfunction. Conclusions: Implantation of self-expanding permanent endoluminal stents for benign ureteral strictures is safe, effective and minimally invasive in select cases. Additional studies and long-term results are needed to make definitive conclusions about this method. KEYWORDS:ureter, stents Since Milroy described the first application of a selfexpanding permanent endoluminal stent in the urethra in 1988,l the next logical step was to use these stents in the ureter. New and modified techniques of implantation were developed t o account for the different anatomical and functional system.' The first application of a self-expanding permanent endoluminal stent in the ureter was reported by Gort et a1 in 1990, who used a Wallstent for a ureteroileal anastomotic stricture. Since then these stents have been used successfully by others for treatment of extrinsic malignant and benign ureteral strictures. Complicated ureteral strictures often lead to permanent urinary diversion or loss of the kidney. Encouraged by our results in malignant extrinsic ureteral obstructi~n,~." we used self-expanding permanent Accepted for publication February 26, 1999 Schneider, Switzerland. NovoMed Inc., Mannheim, Germany. 7 Optimed, Germany,
7
@ :
endoluminal stents in otherwise untreatable patients with benign ureteral strictures. MATERIALS AND METHODS
From March 1994 to May 1998 a self-expanding permanent endoluminal stent was implanted in 13 patients, including 2 with a solitary kidney, in the manner developed and described by us previously.' Mean patient age was 56.8 years and mean followup was 41.6 months (table 1).Implantation was done using the Wallstent, a cobalt chromium nickel molybdenum iron alloy, in 4 patients and the Memotherm or Sinus stent, a nickel titanium alloy, in 9. All patients had scarred ureteral strictures caused by preexisting diseases or interventions (table l),and were unable to undergo open surgery for cardiac or other reasons, or did not want to undergo reoperation. Previous treatments were insufficient or did not meet patient expectations.
TABLE1 Pt. No.
Stricture Length - Sex
-Age
Implantation Side Date
Location
Stent
(cm.) 2-5
Preexisting Disease
Previous
or Intervention
Wallstent
Aortofemoral bypass
1 - F - 52.8
3/4/94
Rt.
Mid ureter
2 - F -55.5 3 - F - 74.8 4 - F - 52.2
3/4/94 5/26/94 6/7/94
Lt. Lt. Rt.
Mid ureter Mid ureter Distal ureter
Greater than 5 2-5 2-5
5 - F -662.7 6 - F -41.4 7 - F -37.9
9/30/94 10/27/94 3/31/95
Rt. Lt. Lt.
Mid ureter Distal ureter Distal ureter
Greater than 5 2-5 2-5
Radiation Crohn's disease Repeated ureteroscopy Mernotherm Radiation Memotherm Bowel surgery Gynecological surgery Wallstent
8-
F -53.8
9/23/96
Lt.
Distal ureter
Greater than 5
Memotherm
91011-
F -64.9 F -83.3 F -73.5
3/7/97 7/16/97 10/1/97
Lt. Rt. Lt.
Mid ureter Mid ureter Distal ureter
Greater than 5 2-5 2-5
Sinus Memotherm Sinus
12-
M -28.3
4/1/98
Rt.
Mid ureter
2-5
Sinus
13-
F -49.1
5/7/98
Lt.
Mid ureter
2-5
Sinus
Wallstent Wallstent Memothe rm
* Nephrectomy was performed after 46.5 months. 319
Percutaneous nephrostomy Double-J Double-J Double-J
Ureterolysis Ureterolysis Percutaneous nephrostorny Gynecological surgery Ureter reimplantation Radiation Double-J Aortofernoral bypass Double-J Urogenital Percutaneous tuberculosis nephrostomy Bilharziasis Ureter reimplantation Retroperitoneal Ureterolysis fibrosis
Primary Patency (mos.)
Assisted Patency (mos.)
54.4 54.43 51.6 51.27 47.4 41.3 23.3 17.8 13.4 10.8 4.8 3.6
320
PERMANENT ENDOLUMINAL STENTS FOR BENIGN URETERAL STRICTURES
FIG. 2. Endoscopic view of stented ureter. Entire foreground represents stent area covered by fine lining of urothelium without edema or hyperplasia. Small part of normal, unstented ureter is seen in background.
TABLE2. Assisted patency No. Pts. 2 2 1
FIG. 1. One year aRer stent im lantation urography reveals normal nondilated upper tract on rig& side. Stent area is marked with 2 arrows. "he technique of implantation followed a standardized procedure.* "he stricture is localized by fluoroscopy, the length of the stricture is determined and an adequate stent is selected. A soft tip guide wire is inserted via a ureteral catheter and the stricture is bypassed with the guide wire. After removal of the ureteral catheter a balloon dilation catheter is inserted over the guide wire and the balloon is located inside the stricture area. The stricture is dilated to a minimum of 5 mm. in diameter, with pressure as needed which sometimes reaches 17 atm. It is important to dilate the stricture adequately to avoid hourglass shape deformation of the stent. After dilation the balloon catheter is replaced by the stent catheter and the stent is released with care. It is advisable to choose a stent which exceeds the stricture at least 5 mm. on both ends to avoid overgrowth and re-obstruction at the ends. Finally, we implant a Double-J* catheter for 4 to 6 weeks to bridge the initial urothelial hyperplasia. To avoid kinking of the ureter in the prevesical area it is important to locate the distal end of the stent inside the intramural part of the ureter, just behind the orifice, thus preventing reflux. Followup was a mean of 41.6 months (range 7 to 55), and included ultrasonography, urography (fig. 1) and scintigraphy with furosemide washout. Ureteroscopy was done only when needed (fig. 2).
Problem
of scar tissue into the lumen of the stent. I n 1patient 2 years after endoscopic removal of the stricture a calculus developed which was too big to pass the stent area of the ureter, and had to be disintegrated and removed endoscopically. Ureteroscopy of the stent area was uneventful and showed normal urothelium. In 2 patients incrustation of a small part of the stent not covered by urothelium developed due to bad apposition to the ureteral wall and was removed endoscopically. Stone analysis revealed a uric acid stone in 1 patient who was given medication. In 1patient obstruction persisted after removal of the Double-J catheter due to incorrect stent placement and another overlapping stent on the proximal end of the stricture was implanted. In 1patient kidney function was only 5% of the overall function of both kidneys at stent implantation and subsequently deteriorated further, and so the kidney had to be removed. The indication to implant a stent in this case was wrong and we consider this a failure. No infection, migration or alteration of other organs was observed. DISCUSSION
Ureteral obstruction constitutes a therapeutic dilemma. Double-J stents, balloon dilation and endoscopic incision do not provide satisfactory results according t o the literature.6-8 However, it is desirable to spare patients the discomfort of a permanent nephrostomy tube or frequent exchange of Double-J catheters. In general, strictures greater than 2 cm., ischemic or in the mid ureter do not respond well to standard endoscopic techniques, such as balloon dilation or incision or ureteral cutting balloon catheter incision. Bal-
RESULTS
Primary patency was achieved in 7 patients with the ureters patent from implantation to date, assisted patency, that is patency achieved with secondary intervention, was achieved in 5 (table 2) and implantation was considered a failure in 1.In 2 patients a stricture recurred due to ingrowth * Medical Engineering Corp., New York, New York.
Treatment
Recurrent stricture Laser ablation inside stent Incrustation Endoscopic removal Misplacement of stent Overlapping implantation of another stent
TABLE 3 %
References
Intervention
Patency
Clayman and Kavoussi'
Balloon dilation Endoscopic-incision (cold knife) Acucise incision Self-expanding permanent endoluminal stent
55 79 73 69.1
Cohen et a18 Various studies from literature
PERMANENT ENDOLUMINAL STENTS FOR BENIGN URETERAL STRICTURES
321
TABLE4 References
No,
FYloyp
No. Patencyl Total No. ll1 444 ll1
Stent/Diameter bun.)
art et a13 Daniels et a19 Sanders et allo
1 4 1
6 9(mean) 7
Newman et all' Reinberg et allz
11 5
3-2 1 6-13
4/11 515
Wallstent /10,8 Wallstent /lo, 8
Noble et all3 Rickards'* Pollack et all'
5 7 6
6-12 6-12 ll(mean)
515 6/7 ll6
Wallstent 16 Wallstent /7 Wallstent /10
Herrero et all6
2
36
2/2
Wallstent /6
Masulovic et al" Lock et a1" Burgos et all9
18 16$ 9
12(mean) 6-90 3-19
8/19 10/16 10/12
Streckert/6,8 Wallstent /7 Memotherm / 4 , 8
Pauer and Lugmay?'
11
7-55
12/13
Wallstent /7 Memothem /8 sinus /7
Wallstent 16 Wallstent /? Palmaz*/?
Conclusions May salvage failed balloon dilation of benign strictures May be useful in seleeted patients with ureterointestinal stricture Can be successful, no success predictors identified Adequate alternative treatment, clinical experience and histology are encouraging Should be considered for post-radiation strictures Role for this method, pt. selection is crucial Wallstents are ineffective in benign ureteroenteric strictures Useful technique in management of strictures aRer kidney transplantation Signiscant better effect than interventional procedures An attractive alternative with good and long lasting results Safe and effective method, further long-term followup is needed Safe and effective, further experimental research and long-term experience are needed
95 3-90 67/97 (69.1) Overall (%) *Johnson & Johnson. Intervention Svstems. Warren. New Jersev. t Boston Scientific Co'rp.,Watertown,- Massachusetts.' $ Including case of Gort et al.3
loon dilation and ureterotomy remain reasonable options for benign ureteral strictures less than 2 cm. Ureterotomy has a higher success rate but requires more expertise and has a higher complication rate. Extreme caution should be exercised when incising strictures in the vicinity of major vessels, especially the iliac vessels. Although patency rates are higher for ureterotomy than self-expanding permanent endoluminal stents, the complication rates for the stents are significantly10wer.~*~ Patency rates of self-expandingpermanent endoluminal stents far exceed balloon dilation and nearly equal the Acucise* procedure (table 3). Several groups have treated benign ureteral strictures with the Wallstent or nitinol stents. A total of 97 cases of benign ureteral strictures were reported with followup beand - ~ the ~ overall success rate tween 3 and 90 m o n t h ~ , 3 . ~ was 69.1% (67 of 97 cases). Positive conclusionswere made in 11of the 12 studies and only 115indicated that this method was ineffective (table 4). Urothelial hyperplasia was described in most cases as the main cause of re-obstruction. However, a metal stent at least provides a buttress for the previously obstructed segment of the ureter, and so the lumen, although decreased by hyperplasia, is held open, which allows eventually an easy exchange of a Double-J stent, which then can provide patency. Urothelial hyperplasia, a main problem of self-expandhg permanent endoluminal stents, eventually can be minimized using biocompatible polymer lined stents.'* Animal experiments with these stents indicated a significant increased patency in ureters treated with lined versus bare stents. Moderate to severe hydroureteronephrosis and significant urothelial hyperplasia with ingrowth through the spaces between the metal wires developed in all animals with bare metal stents, which confirms the results in other animal experiments done in 1995F2Of the animals implanted with lined stents 1 had mild hydroureteronephrosis and there were no papillary ingrowths of urothelium through the stent interstices. This obstructive phenomenon was prevented by the porous polymer lining grossly and histolo~calb'. Different conclusions can be drawn f?om clinical results in humans. Re-obstruction by urothelial hyperplasia is a common problem which does not necessarily occur in dl patients, nor is it a persistent phenomenon. To our knowledge the only description ofa histological specimen of a removed but patent self-expanding permanent endoluminal stent W= r e p o d by Reinberg et d.12Stent material or design obviously does * Applied Medical Resources, Laguna Hills, California.
not have any effect on the outcome of the relief of obstruction, although hydrodynamic considerations suggest a conical shape (angulation 3 to 4 degrees) to minimize outflow resistance at the distal end of the self-expanding permanent endoluminal stent. Stent diameter, however, needs to be considered as re-obstruction by hyperplasia can probably occur more easily with small diameters. A diameter of 7 mm. is recommended to enable later endoscopic procedures. In conclusion, with careful patient selection implantation of selfexpanding permanent endoluminal stents seems safe and effective for otherwise untreatable patients with benign ureteral strictures. Further clinical experience with long-term results and experimental studies are needed. REFERENCES
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