Stenting for MUO
Editorial Comment Editorial Comment to Stenting for malignant ureteral obstruction: Tandem, metal or metal-mesh stents I would like to congratulate Elsamra et al. for publishing a very comprehensive and up-to-date review.1 Although placement of a ureteral stent might be one of the most common procedures for the current urologist, the concept of a ureteral stent was not recognized until 1976 when Dr Gibbons introduced the ureteral “stent” in urological practice.2 Furthermore, it was 1978 when Dr Finney developed the current most popular double-J shaped silicon stent.3 The silicon stent has been widely used for over 30 years. As placement of a silicon stent still cause encrustation, obstruction and infection, modifications have been made to the design, size and material of the stents. However, limitations remain, such as the need for periodical exchange within 3–6 months or the inability to counteract external pressure, such as secondary to a malignant tumor. In order to counteract these limitations of the silicon stent, metal stents have been adopted to ureter from blood vessel.4,5 However, one of the confronting limiting factors was that the ureter has a peristaltic function in order to maintain the urinary flow and is not just a resting tube, like vessels. This characteristic will cause the problem known as “stent migration.” Furthermore, a ureteral stent needs to be removed, not like a vascular stent that can be placed permanently, because urine sometimes contains debris or even microbacteria, so a ureteral stent will eventually result in obstruction or infection, which will eventually cause renal failure or pyelonephritis.4,5 As the authors mentioned, there have been a number of stenting approaches that have been useful against extrinsic malignant compression. A tandem stent might be most costeffective approach, if (unless) patients are capable of exchanging at short intervals. Resonance metal stents have been widely used, but with complications of urinary tract infections and severe lower urinary tract symptoms as a result of their metal component. Metal-mesh stents show a high success rate at first, but also result in obstruction and migration. Recently, at the 103rd Annual Meeting of the Japanese Urological Association, Dr Han from Samsung Medical Center provided novel experience regarding 90 consecutive Uventa metallic stent (Taewoong Medical, Gyeonggi-do, Korea) cases, and reported 70.8% and 84.2% success rates
© 2015 The Japanese Urological Association
with benign and malignant obstructive cases, respectively, with a total of 25.0% of stent migration (JUA-Oral-06). Dr Chow from National Taiwan University Hospital reported their experience with the 42 Resonance metallic stent (Cook Medical, Bloomington, IN, USA) cases in malignant ureteral obstruction. They reported increase of 4 months in functional duration of Resonance stents compared to regular double-J stents (P < 0.0001), and 50% of the Resonance stents had increase in functional duration more than 3 months (JUA-Oral-07). Although metallic stents seems to be promising tools for ureteral stricture, no definitive indication exists regarding how and which metal stent should be used in a specific ureteral stricture. An accumulation of evidence including randomized, prospective, control trials of malignant/benign ureteral strictures will be required to establish the clinical evidence for metal stents. Shinichi Sakamoto M.D., Ph.D. Department of Urology, Chiba University Graduate School of Medicine, Chiba, Japan [email protected] DOI: 10.1111/iju.12835
Conflict of interest None declared.
References 1 Elsamra SE, Leavitt DA, Motato HA et al. Stenting for malignant ureteral obstruction: Tandem, metal or metal-mesh stents. Int. J. Urol. 2015; 22: 629–36. 2 Gibbons RP, Correa RJ Jr, Cummings KB, Mason JT. Experience with indwelling ureteral stent catheters. J. Urol. 1976; 115: 22–6. 3 Finney RP. Experience with new double J ureteral catheter stent. J. Urol. 1978; 120: 678–81. 4 Yachia D. Recent advances in ureteral stents. Curr. Opin. Urol. 2008; 18: 241–6. 5 Yachia D. Metal ureteral stents in chronic obstructions. Indian J. Urol. 2011; 27: 307–9.
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Editorial Comment Editorial Comment to Stenting for malignant ureteral obstruction: Tandem, metal or metal-mesh stents I would like to congratulate Elsamra et al. for publishing a very comprehensive and up-to-date review.1 Although placement of a ureteral stent might be one of the most common procedures for the current urologist, the concept of a ureteral stent was not recognized until 1976 when Dr Gibbons introduced the ureteral “stent” in urological practice.2 Furthermore, it was 1978 when Dr Finney developed the current most popular double-J shaped silicon stent.3 The silicon stent has been widely used for over 30 years. As placement of a silicon stent still cause encrustation, obstruction and infection, modifications have been made to the design, size and material of the stents. However, limitations remain, such as the need for periodical exchange within 3–6 months or the inability to counteract external pressure, such as secondary to a malignant tumor. In order to counteract these limitations of the silicon stent, metal stents have been adopted to ureter from blood vessel.4,5 However, one of the confronting limiting factors was that the ureter has a peristaltic function in order to maintain the urinary flow and is not just a resting tube, like vessels. This characteristic will cause the problem known as “stent migration.” Furthermore, a ureteral stent needs to be removed, not like a vascular stent that can be placed permanently, because urine sometimes contains debris or even microbacteria, so a ureteral stent will eventually result in obstruction or infection, which will eventually cause renal failure or pyelonephritis.4,5 As the authors mentioned, there have been a number of stenting approaches that have been useful against extrinsic malignant compression. A tandem stent might be most costeffective approach, if (unless) patients are capable of exchanging at short intervals. Resonance metal stents have been widely used, but with complications of urinary tract infections and severe lower urinary tract symptoms as a result of their metal component. Metal-mesh stents show a high success rate at first, but also result in obstruction and migration. Recently, at the 103rd Annual Meeting of the Japanese Urological Association, Dr Han from Samsung Medical Center provided novel experience regarding 90 consecutive Uventa metallic stent (Taewoong Medical, Gyeonggi-do, Korea) cases, and reported 70.8% and 84.2% success rates
© 2015 The Japanese Urological Association
with benign and malignant obstructive cases, respectively, with a total of 25.0% of stent migration (JUA-Oral-06). Dr Chow from National Taiwan University Hospital reported their experience with the 42 Resonance metallic stent (Cook Medical, Bloomington, IN, USA) cases in malignant ureteral obstruction. They reported increase of 4 months in functional duration of Resonance stents compared to regular double-J stents (P < 0.0001), and 50% of the Resonance stents had increase in functional duration more than 3 months (JUA-Oral-07). Although metallic stents seems to be promising tools for ureteral stricture, no definitive indication exists regarding how and which metal stent should be used in a specific ureteral stricture. An accumulation of evidence including randomized, prospective, control trials of malignant/benign ureteral strictures will be required to establish the clinical evidence for metal stents. Shinichi Sakamoto M.D., Ph.D. Department of Urology, Chiba University Graduate School of Medicine, Chiba, Japan [email protected] DOI: 10.1111/iju.12835
Conflict of interest None declared.
References 1 Elsamra SE, Leavitt DA, Motato HA et al. Stenting for malignant ureteral obstruction: Tandem, metal or metal-mesh stents. Int. J. Urol. 2015; 22: 629–36. 2 Gibbons RP, Correa RJ Jr, Cummings KB, Mason JT. Experience with indwelling ureteral stent catheters. J. Urol. 1976; 115: 22–6. 3 Finney RP. Experience with new double J ureteral catheter stent. J. Urol. 1978; 120: 678–81. 4 Yachia D. Recent advances in ureteral stents. Curr. Opin. Urol. 2008; 18: 241–6. 5 Yachia D. Metal ureteral stents in chronic obstructions. Indian J. Urol. 2011; 27: 307–9.
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