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

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. Copyright:

INTRODUCTION

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.[56] 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

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)

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

DISCUSSION

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

Lead author	Year	Patient age	Sex	Side	Location of knot	Stent configuration	Indication for stent	Removal	Laser	Complications	Postremoval nephrostomy
Quek and Dunn[9]	2002	66	Female	Right	Mid-portion	7 Fr 24 cm Double J	Renal stone	Cystoscopy and distal traction	No	None	Not recorded
Bhirud et al.[10]	2012	41	Male	Right	Mid-portion	Double J	Renal stone	Percutaneous using 26 Fr nephroscope	No	Hydronephrosis	Not recorded
Moufid et al.[11]	2012	32	Male	Left	Proximal	Double J	Ureteral stone	Gentle continuous traction under fluoroscopic guiding	No	Hydronephrosis, urosepsis	Not recorded
Picozzi and Carmignani[5]	2010	41	Female	Right	Proximal	Double J	Ureteral injury following surgery	Cystoscopy and continuous traction	No	None	Not recorded
Kim et al.[4]	2015	53	Male	Right	Proximal	Double J	Renal and ureteral stone	Percutaneous. antegrade	No	Not recorded	Yes
Kundargi et al.[12]	1994	53	Male	Left	Proximal	6 Fr 26 cm Double J	Renal stone	Percutaneous	No	None	Not recorded
Ahmadi et al.[13]	2015	45	Male	Left	Proximal	6 Fr doUble J, Multi-Length Soft	Renal stone	Cutting of stent using holmium YAG laser. Remaining stent fragment retrieved with a basket	Yes	None	Not recorded
Ahmadi et al.[13]	2015	43	Male	Left	Proximal	6 Fr Double J, Multi-Length Stiff	Ureteral stone	Cutting of stent using holmium YAG laser. Remaining stent fragment retrieved with a basket	Yes	None	Not recorded
Ahmadi et al.[13]	2015	71	Male	Right	Proximal	7 Fr Double J	Retroperitoneal fibrosis secondary to treated lymphoma	Percutaneous	Yes (unsuccessfully)	None	Not recorded
Ahmadi et al.[13]	2015	71	Male	Left	Proximal	7 Fr Double J	Retroperitoneal fibrosis secondary to treated lymphoma	Percutaneous	No	None	Not Recorded
Ahmadi et al.[13]	2015	52	Male	Right	Proximal	6 Fr Double J, Multi-length	Ureteral stone	A combination of rigid and flexible pyeloscopy was used with holmium laser to remove all encrustation of the proximal stent, “Undo” the knot and retrieve the stent entirely over a wire	Yes	Not recorded	Not recorded
Kondo et al.[14]	2005	37	Male	Left	Proximal	6 Fr Double J, Multi-Length	Renal stone	Open ureterotomy	No	None	Not recorded
Baldwin et al.[15]	1998	73	Male	Left	Proximal	7Fr Multi-Length Double J	Transitional cell carcinoma	Amplatz Super Stiff Wire inserted through lumen of stent to untie knot	No	None	No
Basavaraj et al.[16]	2007	70	Female	Right	Proximal	6 Fr Multi-Length Double J	Renal and ureteral stone	Rigid conduitoscopy	No	None	Not recorded
Braslis and Joyce[17]	1992	37	Female	Right	Proximal	4.7 Fr Multi-Length Double J	Renal stone	Percutaneous	No	None	Yes
Corbett and Dickson[18]	2005	4	Male	Not recorded	Proximal	4.7 Fr Multi-Length Double J	Reimplantation of an obstructed megaureter	Cystoscopy and distal traction	No	Hydronephroureter	No
Das and Wickham[19]	1990	45	Male	Right	Distal	Single J (Length Not Recorded)	Renal stone	Cystoscopy and distal traction	No	None	Not recorded
Flam et al.[20]	1995	86	Male	Left	Proximal	6 Fr 26cm Double J	Ureteral stone	Ureteroscopy and retraction of knot	No	None	Not recorded
Karagüzel et al.[21]	2012	53	Male	Right	Proximal	4.7 Fr 28-Cm Double-J Stent	Ureteral stone	Ureterorenoscopy under general anaesthesia. Knotted stent extracted using foreign body forceps	No	None	Not recorded
Nettle et al.[22]	2012	43	Male	Right	Proximal	6 Fr Double J (length not recorded)		Holmium laser	Yes	Not recorded	Not recorded
Richards Nettle et al.[7]	2011	67	Male	Left	Proximal	Not recorded	Ureteral stone	Ureterorenoscopy and holmium laser	Yes	Not recorded	Not recoded
Rivalta et al.[23]	2009	83	Male	Right	Proximal	7 Fr (Length Not Recorded)	Bladder and prostate cancer	Sterile Vaseline applied through the cutaneous stoma, then gentle traction	No	None	No
Sighinolfi et al.[24]	2005	48	Male	Right	Proximal	5 Fr Multi-Length Double J	Renal stones	3 days continuous slight traction	No	Hydronephrosis	Not recorded
Zhou et al.[25]	2018	33	Male		Proximal	6 Fr 26cm Double J	Postoperative ureterovesical anastomotic stricture	Holmium laser, stent fragments cleared by stone basket extractor	Yes	None	No
Eisner et al.[26]	2006	82	Female	Left	Proximal	Cook Kwart Retro-Inject 6F×22-32 Cm	Renal stones	Gentle traction following several forceful coughs	No	None	Not recorded
Tempest et al.[27]	2011	68	Male	Left	Proximal	6F Multi-Length	Renal stones	Laser cut knot into two pieces which were removed separately, using the tri-radiate graspers	Yes	None	Not recorded

YAG: Yttrium-aluminum-garnet

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.[2324] 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[410121317] 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

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.

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

Nil.

Conflicts of interest

There are no conflicts of interest.