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Table of Contents
Year : 2020  |  Volume : 12  |  Issue : 1  |  Page : 96-100  

Antegrade removal of a knotted ureteric stent: Case report and review of literature

1 Medical Student, University of Leeds, Leeds Teaching Hospitals NHS Trust, Leeds, England
2 Department of Radiology, Leeds Teaching Hospitals NHS Trust, Leeds, England
3 Department of Urology, Leeds Teaching Hospitals NHS Trust, Leeds, England

Date of Submission16-Dec-2018
Date of Acceptance16-May-2019
Date of Web Publication23-Dec-2019

Correspondence Address:
Mr. Chandra Shekhar Biyani
Leeds Teaching Hospitals NHS Trust, St James University Hospital Leeds, Beckett Street, LS9 7TF, Leeds
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DOI: 10.4103/UA.UA_172_18

PMID: 32015629

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Ureteral stents are routinely used in urological practice for many indications including obstruction of ureter, ureteral stricture, prior to treatment with extracorporeal shock wave lithotripsy, and to promote healing following ureteral injury. Complications reported with ureteric stents include stent migration, stent rupture, encrustation, ureteral perforation, erosion, and fistulation. Knotting of an indwelling ureteral stent is a very rare complication, with fewer than 30 cases reported in the literature. Techniques for managing this complication include using a holmium laser to cut the knot, percutaneous antegrade removal, and gentle traction. We describe the case of a knotted stent and its removal along with a comprehensive literature review.

Keywords: Knotted stents, knotted ureteric stents, ureteric stents

How to cite this article:
Bradshaw J, Khan A, Adiotomre E, Burbidge S, Biyani CS. Antegrade removal of a knotted ureteric stent: Case report and review of literature. Urol Ann 2020;12:96-100

How to cite this URL:
Bradshaw J, Khan A, Adiotomre E, Burbidge S, Biyani CS. Antegrade removal of a knotted ureteric stent: Case report and review of literature. Urol Ann [serial online] 2020 [cited 2020 Mar 29];12:96-100. Available from: http://www.urologyannals.com/text.asp?2020/12/1/96/273870

   Introduction Top

Ureteral stents were first described over five decades ago by Zimskind et al.[1] and are widely used in current urological practice. Indications for ureteral stenting include obstruction of the ureter, ureteral stricture,[1] prior to treatment with extracorporeal shock wave lithotripsy, identification of ureter during pelvic surgery,[2] to promote healing following ureteral injury,[3] and protection of ureteral anastomosis in urinary diversion.[4] Complications reported with ureteral stents include stent migration, stent rupture, encrustation, ureteral perforation, erosion, and fistulation.[5],[6] An unusual complication is knot formation of the indwelling ureteral stent; this is very rare, with fewer than 30 cases reported in the literature. We searched previous reports using the MEDLINE database and the specific keywords “knotted stents” and “knotted ureteric stents.” All English language articles were reviewed. We describe our experience of a knotted stent alongside a detailed review of the literature.

   Case Report Top

We present the case of a 57-year-old female with a previous history of radiotherapy for cervical cancer. Unfortunately, she developed a very abnormal bladder with bilateral vesicoureteric junction strictures following radiotherapy. She was initially managed conservatively along with bilateral ureteric stents. Her symptoms of dysuria and leakage were very bothersome, and she was unable to tolerate a catheter. The decision was made to perform a cystectomy with ileal conduit formation.

Following surgery, her left ureteric stent was removed, but the right-sided stent could not be removed as it had migrated into the ureter. Her renal function deteriorated subsequently, and she had a right-sided nephrostomy placed.

Following nephrostomy, an attempt was made to snare the right ureteric stent through an antegrade approach under a local anesthetic and sedation. The nephrostomy was removed over a guidewire and exchanged for an 8Fr sheath. BMC/Terumo and Amplatz wires were negotiated down the ureter past the stent. Attempts were made at snaring with 20 mm, 10 mm, and 5 mm gooseneck loop and small basket snares. Snaring was successful with a 5 mm snare. Unfortunately, the stent formed a knot on withdrawing and could not be removed. Attempts were made to untie the knot and snare the knot unsuccessfully [Figure 1]. The patient was unable to tolerate any further attempts at removal under local anesthetic and sedation. A second wire was placed alongside the stent and a new 8.5Fr right nephrostomy placed.
Figure 1: Right ureteric stent knotted during removal (arrow showing knot)

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Further attempts at stent removal were done in theater under a general anesthetic. The nephrostomy position was confirmed and exchanged for an Amplatz/BMC. An attempt to pass a guidewire in the conduit was unsuccessful. Conduitogram demonstrated no filling of the right ureter. An Amplatz wire was placed down the stent into the renal pelvis, and the tract was dilated using serial metal dilators up to 15fr. The stent and wire were then withdrawn together through the tract without difficultly [Figure 2]. A new 8.5Fr right-sided nephrostomy was placed without any immediate complications.
Figure 2: Knotted stent with guidewire through a side hole postremoval

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   Discussion Top

The increasing use of ureteral stents in urological practice has resulted in an increased frequency of complications associated with them.[7] However, knotting of an indwelling ureteral stent is still a rare complication. A search of the MEDLINE database revealed 27 cases of knotted stents (24 papers) including one pediatric case and one case following renal transplantation. All papers in the English language were reviewed and one non-English report, published in German, was excluded.[8] In the remaining 26 cases, the patients' ages ranged from 4 to 86, with a male to female ratio of 4:1. Renal and/or ureteral stones were the most common indication for the ureteral stent. In the vast majority of cases, the knot was reported in the proximal end, two formed in the mid-section and one was reported in the distal portion. The patient data are summarized in [Table 1].
Table 1: Review of the literature on knotted ureteric stents

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It is unclear exactly what causes knot formation in an indwelling ureteral stent. Excessive stent length, coil formation, and individual patient factors such as renal pelvis dilatation have been hypothesized as causes for this rare complication. Multi-length stents (used in 10 cases) are associated with lower risks of migration but potentially have a higher risk of knotting;[5] thus optimal selection of stent length may help prevent knotting. The experience of the surgeon has also been hypothesized as a contributing factor following a high frequency of cases reported at a single institution during 1-year period.[13] Careful real-time fluoroscopic imaging during stent removal aids in preventing stent knotting.

At present, there are no guidelines on how to manage this complication. Poor management can result in serious consequences such as major ureteric injury or loss of the kidney.[13] Various techniques for removal of the knotted stent have been recorded. Gentle traction has been used in eight cases to remove the knotted stent, including Rivalta et al. who used sterile Vaseline within the ureterocutaneostomy, and Sighinolfi et al. where the stent was attached to the patient's leg and 3 days of continuous gentle traction achieved removal.[23],[24] Eisner et al. reported a unique case where a series of forceful coughs from the patient produced Valsalva effect allowing the proximal knot to unite spontaneously which could subsequently be removed by gentle traction.[26] The risk of serious ureteral trauma should be considered when removing the knotted ureteral stent with traction, especially if strong resistance is encountered.[5]

Another minimally invasive method for removal is untying the knot in situ which has been done in two cases. Baldwin et al. inserted Amplatz super stiff guidewire through the stent lumen to successfully untie the knot before removal by traction[15] and Flam et al. untied the knot using 5F alligator forceps during ureteroscopy.[20] More invasive procedures such as using percutaneous removal[4],[10],[12],[13],[17] or open ureterotomy[14] have been described when conservative methods have been unsuccessful.

The use of a holmium laser to fragment the knotted stent was first described by Richards et al.[7] as a minimally invasive alternative to other methods of removal. It has since been used successfully in eight cases. Due to its safety and noninvasive approach, it has been recommended as a first-line treatment for the removal of a knotted stent.[13] Limitations of this approach include ureteric strictures, which prevent the advancement of the ureteroscope to the level of the knot as encountered by Ahmadi et al.

   Conclusion Top

Knotted ureteral stents are a rare complication of stent use. Poor management can result in serious consequences for the patient. Various techniques have been described for removal including gentle traction, percutaneous removal, open ureterotomy, and using a holmium laser. Antegrade removal of a knotted stent as described is a reliable and safe method of removal in select cases, especially where antegrade access is already available.[27]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Zimskind PD, Fetter TR, Wilkerson JL. Clinical use of long-term indwelling silicone rubber ureteral splints inserted cystoscopically. J Urol 1967;97:840-4.  Back to cited text no. 1
Redan JA, McCarus SD. Protect the ureters. JSLS 2009;13:139-41.  Back to cited text no. 2
Kim JH, Moore C, Jones JS, Rackley R, Daneshgari F, Goldman H, et al. Management of ureteral injuries associated with vaginal surgery for pelvic organ prolapse. Int Urogynecol J Pelvic Floor Dysfunct 2006;17:531-5.  Back to cited text no. 3
Kim MS, Lee HN, Hwang H. Knotted stents: Case report and outcome analysis. Korean J Urol 2015;56:405-8.  Back to cited text no. 4
Picozzi S, Carmignani L. A knotted ureteral stent: A case report and review of the literature. Urol Ann 2010;2:80-2.  Back to cited text no. 5
[PUBMED]  [Full text]  
Ahallal Y, Khallouk A, El Fassi MJ, Farih MH. Risk factor analysis and management of ureteral double-j stent complications. Rev Urol 2010;12:e147-51.  Back to cited text no. 6
Richards MM, Khalil D, Mahdy A. Successful treatment of stent knot in the proximal ureter using ureteroscopy and holmium laser. Case Rep Med 2011;2011:502191.  Back to cited text no. 7
Kadner G, Richter M, Romer H, Jurczok A. Correction and solution of wrongly placed and knotted ureteral stent. Aktuelle Urol 2009;40:71.  Back to cited text no. 8
Quek ML, Dunn MD. Knot formation at the mid portion of an indwelling ureteral stent. J Urol 2002;168:1497.  Back to cited text no. 9
Bhirud P, Giridhar V, Hegde P. Midureteric knotted stent removed by percutaneous access! Urol Ann 2012;4:106-7.  Back to cited text no. 10
Moufid K, Touiti D, Mohamed L. “Knot stent”: An unusual cause of acute renal failure in solitary kidney. J Clin Imaging Sci 2012;2:36.  Back to cited text no. 11
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Kundargi P, Bansal M, Pattnaik PK. Knotted upper end: A new complication in the use of an indwelling ureteral stent. J Urol 1994;151:995-6.  Back to cited text no. 12
Ahmadi N, Tran M, Elms M, Ko R. Knotted proximal loop of ureteric stents: Review of the literature and five case reports. J Clin Urol 2015;8:432-7.  Back to cited text no. 13
Kondo N, Yoshino Y, Shiono Y, Hasegawa Y. A case demonstrating knot formation at the upper end of a ureteral stent. Hinyokika Kiyo 2005;51:385-7.  Back to cited text no. 14
Baldwin DD, Juriansz GJ, Stewart S, Hadley R. Knotted ureteral stent: A minimally invasive technique for removal. J Urol 1998;159:2065-6.  Back to cited text no. 15
Basavaraj DR, Gill K, Biyani CS. Case report: Knotted ureteral stent in patient with ileal conduit: Conservative approach for retrieval. J Endourol 2007;21:90-3.  Back to cited text no. 16
Braslis KG, Joyce G. Spontaneous knotting of a pigtail ureteric stent in the ureter requiring percutaneous removal. Aust N Z J Surg 1992;62:825-6.  Back to cited text no. 17
Corbett HJ, Dickson AP. Knotting of a ureteric stent in a child. Int Urol Nephrol 2005;37:493-4.  Back to cited text no. 18
Das G, Wickham JE. Knotted ureteric stent: An unusual urological complication. J R Coll Surg Edinb 1990;35:190.  Back to cited text no. 19
Flam TA, Thiounn N, Gerbaud PF, Zerbib M, Debré B. Knotting of a double pigtail stent within the ureter: An initial report. J Urol 1995;154:1858-9.  Back to cited text no. 20
Karagüzel E, Kutlu O, Kazaz IO, Gür M, Dil E, Ozgür GK. Knotted ureteral stent: A rare complication of ureteral stent usage. Urol Res 2012;40:793-5.  Back to cited text no. 21
Nettle J, Huang JG, Rao R, Costello AJ. Ureteroscopic holmium laser ablation of a knotted ureteral stent. J Endourol 2012;26:968-70.  Back to cited text no. 22
Rivalta M, Sighinolfi MC, Micali S, De Stefani S, Bianchi G. Knotted ureteral catheter in an 83-year-old man: Case presentation and urological non-invasive management in the elderly. Urol Res 2009;37:261-2.  Back to cited text no. 23
Sighinolfi MC, De Stefani S, Micali S, Mofferdin A, Baisi B, Celia A, et al. Aknotted multi-length ureteral stent: A rare complication. Urol Res 2005;33:70-1.  Back to cited text no. 24
Eisner B, Kim H, Sacco D. Repeat knot formation in a patient with an indwelling ureteral stent. Int Braz J Urol 2006;32:308-9.  Back to cited text no. 25
Zhou YH, Chu X, Yi Y, Lei J, Huang S, Dai YB. A knotted ureteral stent in patient with renal transplantation: A case report and literature review. Int J Clin Exp Med 2018;11:6364-8.  Back to cited text no. 26
Tempest H, Turney B, Kumar S. Novel application of an established technique for removing a knotted ureteric stent. BMJ Case Rep 2011;2011. pii: bcr1120103528.  Back to cited text no. 27


  [Figure 1], [Figure 2]

  [Table 1]


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