{"paper_id":"ea0ad987-832b-4daa-87c9-8b018f0c76d8","body_text":"Kolu and Akan  \nJournal of Medical Case Reports          (2024) 18:103  \nhttps://doi.org/10.1186/s13256-024-04395-5\nCASE REPORT Open Access\n© The Author(s) 2024. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which \npermits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the \noriginal author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or \nother third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line \nto the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory \nregulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this \nlicence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecom-\nmons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.\nJournal of\nMedical Case Reports\nSpontaneous knot formation complication \nof double J: two case reports\nAhmet Can Kolu1*   and Serkan Akan1   \nAbstract \nBackground Use of ureteral stents has become an integral part of urological practice. However, it also brought \nwith it many complications. Double J (DJ) stent knotting is a rare stent complication, and only a few cases have been \nreported in the literature. Although the exact cause is unknown and, in the literature, it is generally thought that knots \noccur due to traction. In this case report we present for the first time that spontaneous knots can occur due to ure-\nteral peristalsis or ureteral anomalies.\nCase presentation Two patients (67 and 35 aged-Caucasian person) with ureteral stones who presented \nto the emergency department with colicky pain and had no previous history of urological surgery. We observed knot \nformation in the routine urinary system radiographs taken before stent removal in two patients whose ureters were \nobserved to be narrow during endoscopic ureteral stone treatment. The stents were successfully removed using gen-\ntle traction under general anesthesia.\nConclusions We discussed the cause and solution of spontaneous knot formation. We emphasized the importance \nof the direct urinary system radiograph taken before DJ stent removal.\nKeywords Knotted ureteral stent, Urological complication, Ureteral stent\nIntroduction\nThe ureteral stents, which become an integral part of \nmodern urological practice, provide urinary tract access, \ndilation of urinary strictures, removal of kidney stones, \nand temporary drainage of urine. There are various size \n(14–32 cm), diameter (3–8 F), hardness, body, tip shapes \n(pigtail, double pigtail-JJ) and coating (carbon, hydro -\nphilic, heparin) ingredients for the purpose of use.\nDuring their time with ureteral stents, 80% of patients \nreport experiencing some degree of discomfort. Addi -\ntionally, the use of ureteral stents may lead to serious \ncomplications such as stent migration and stent encrusta-\ntion. Although spontaneous knotting of the ureteral stent \nhas been reported before, it is one of the rare complica -\ntions in the literature. There are a variety of techniques \nreported for the removal of a knotted double J (DJ) stent, \nfrom simple traction to open surgery.\nCase report\nThe first case, a 67-year-old man (Caucasian), applied \nto our clinic with a complaint of left side pain that had \nbeen going on for a month. On physical examination, \npositive left costovertebral angle (CVA) tenderness was \nobserved (Table  1). He had hypertension and diabe -\ntes. There was a stone disease in his father. The patient \nhad no previous history of renal colic, urinary system \nstone disease or any surgical intervention. In the imag -\ning performed for the patient, “Grade 2 ectasia in the \nupper collecting system of the left kidney, double ure -\nter appearance on the left and suspicious stone image \nat the level of the left iliac crossover” was observed; \nureterorenoscopy (URS) was planned for the patient. \n*Correspondence:\nAhmet Can Kolu\nahmetkolu@gmail.com\n1 Department of Urology, University of Health Sciences, Fatih Sultan \nMehmet Research & Training Hospital, 34758 Istanbul, Turkey\n\nPage 2 of 7Kolu and Akan  Journal of Medical Case Reports          (2024) 18:103 \nDuring cystoscopy, a close monitoring of the patient’s \nleft ureteral orifice revealed an attempt to insert a sen -\nsor guide. However, it failed to transition from the mid -\ndle ureter to the proximity. Then, the distal ureter was \nentered through the left ureteral orifice by applying \nureteral balloon dilation under the guidance of a sensor \nguide. The ureter at the iliac cross level was passed with \ndifficulty, but due to stenosis, it could not be advanced \nfurther proximally; 4.8 Fr 26  cm DJ was placed and it \nwas seen that both ends were bent under fluoroscopy.\nThe second case (Caucasian), aged 35, had complaints \nof right-side pain for four months. On physical exami -\nnation, positive right CVA tenderness was observed \n(Table  1). The patient had no comorbidity. There was \na stone disease in his family. A calculus of 3–4  mm in \nsize was observed in the right distal ureter in the imag -\ning performed on the patient, who had a previous his -\ntory of passing spontaneous urinary system stones but \ndid not have a previous surgical history. During the URS \nprocedure performed 2 weeks later, annular stenosis was \nobserved 2  cm ahead of the right orifice and was cor -\nrected with balloon dilatation. Endoscopic ureteral stone \ntreatment was performed with holmium laser. At the end \nof the surgery, a 4.8 Fr 26 cm DJ was placed into the right \nureter and the procedure was terminated. No periop -\nerative or postoperative complications were observed in \nboth cases, and the urinary system was visualized on the \nradiography on the first day after the operation (Fig.  1A, \nB).\nIn both cases, when the urinary system radiographs \nwere repeated six weeks later for routine DJ stent \nremoval; spontaneous knotting was observed at the prox-\nimal end of the DJ stents (Fig.  2A, B). Both of patients no \nbothersome symptoms were reported, and the physical \nexamination was strictly normal. Considering the possi -\nbility that the procedure could be complicated, DJ stent \nremoval was planned under general anesthesia. After \nthe distal coil of the DJ stents was corrected, gentle trac -\ntion was applied toward the contralateral bladder wall. \nDJ stents were barely removed without complications, \nand proximal ends were found to be coming in knotted \n(Fig. 3A, B). A 7Fr ureteral catheter was placed over the \nguide wire to the renal pelvis. The ureteral catheter was \nremoved on postoperative day 1; After observation, the \npatient was discharged with nonsteroidal anti-inflamma -\ntory drug (NSAII) and antibiotic treatment.\nDiscussion\nUreteral DJ stent complications include irritative mictu -\nrition symptoms, suprapubic pain, costovertebral pain, \nvesicorenal reflux, stent malposition, hematuria, uri -\nnary tract infection, fever, encrustation, stent migration, \nstent rupture, ureteral perforation, erosion and fistuliza -\ntion. To our best knowledge, only a few cases have been \nidentified in the literature since Groeneveld et  al. first \nreported it in 1989 [1]. Table  2 summarized the previ -\nously recent published cases regarding DJ stent knot -\nting. Knotted formation is a rare complication, with only \n40 cases being described and can be vexing to manage. \nIn the vast majority of reported cases (92.5%), knotting \nwas observed at the proximal end of the DJ stent. In our \npatients and in the majority of other cases of knotting, \nthe patients were asymptomatic and the cases typically \npresented with unexpected resistance during DJ stent \nremoval.\nIn the majority of reported cases, no abnormal appear -\nance was detected in the urinary system radiograph taken \nbefore stent removal [2], which would suggest knotting in \nthe DJ stent; it has been stated that the knot may form \ndue to traction during extraction. However, in our cases, \nknot formation was observed to develop spontaneously \nimmediately after URS, without any intervention or trac -\ntion. This suggests that knot formation may develop due \nto the ureter’s own peristalsis or secondary to balloon \ndilatation applied to the abnormal ureter.\nIn approximately one-third of reported cases, the DJ \nstent could be removed with gentle traction and the con -\ndition was treated successfully [3]. However, this proce -\ndure carries risks for these patients as it may make the \nexisting knot tighter and increase the degree of compli -\ncations. If strong resistance is encountered during DJ \nstent removal, alternative interventions should be con -\nsidered to avoid causing serious ureteral trauma or loss \nof renal function [3]. In previous years, “the use of ster -\nile Vaseline in addition to traction” has been tried; There \nTable 1 Timeline\nTime intervals are the same for both patients\nURS Ureterorenoscopy\nTime (t) t0 t1 t2 t3\nImportant dates Initial presentation After 2 weeks (URS time) 1 day after URS 6 weeks after URS\n\nPage 3 of 7\nKolu and Akan  Journal of Medical Case Reports          (2024) 18:103 \n \nare suggestions such as “securing the distal end of the DJ \ncatheter to the leg with a catheter band and providing \ncontinuous traction for 3 days” or “applying extracorpor-\neal shock wave lithotripsy (ESWL) to the migrated area of \nthe knotted stent” [4].\nIn another case where knot formation was observed \ntwice in the same patient, no additional intervention \nwas required to open the second knot formation; spon -\ntaneous resolution of the node has been associated with \nthe Valsalva effect achieved by recurrent severe coughs \n[5]. Valsalva has been suggested as an easy and harm -\nless treatment before invasive procedures for removing \nknotted stents.\nBaldwin et al. used an “ Amplatz 0.038 super stiff guide-\nwire” at the proximal end of the stent to solve knot for -\nmation [6]. Flam et  al. placed a second ureteral stent \nnext to the knotted stent, and a week later, the stent was \nremoved with 5Fr alligator forceps [7]. Endourologically, \nbreaking down the knot formation with a holmium laser \nand removing the stent has been suggested in the litera -\nture as another method [8]. Removal of knot-forming \nstents via percutaneous or open surgery should only be \nperformed after failure with other techniques. Urologists \nshould be aware of the possibility of knot formation in \nthe stent if difficulty is encountered during stent removal.\nFig. 1 A Case 1 direct urinary system graphic after Ureterorenoscopy. B Case 2 direct urinary system graphic after Ureterorenoscopy\n\nPage 4 of 7Kolu and Akan  Journal of Medical Case Reports          (2024) 18:103 \nConclusion\nAlthough the literature shows that a knot can occur with \ntraction during DJ stent removal, we also believe that a \nspontaneous node may be caused by ureteral peristalsis \nor ureteral anomalies. Therefore, the routine use of a uri-\nnary system graph (X) for all patients before the release \nof the DJ stent can prevent potential complications due \nto spontaneous knot formation.\nEven if we do not see knot formation on the x-ray, in all \ncases with ureteral stent in which difficulty is experienced \nduring removal, the possibility of stent knotting should \nalways be kept in mind and therapy planned accordingly.\nFig. 2 A Case 1 direct urinary system graphic taken before Double J removal. B Case 2 direct urinary system graphic taken before Double J removal\n\nPage 5 of 7\nKolu and Akan  Journal of Medical Case Reports          (2024) 18:103 \n \nFig. 3 A Case 1 Double J ureteral stent with knot formation at proximal end. B Case 2 Double J ureteral stent with knot formation at proximal end\n\nPage 6 of 7Kolu and Akan  Journal of Medical Case Reports          (2024) 18:103 \nAbbreviations\nCVA  Costovertebral angle\nDJ  Double J\nESWL  Extracorporeal shock wave lithotripsy\nNSAII  Nonsteroidal anti-inflammatory drug\nPCN  Percutaneous nephrostomy\nURS  Ureterorenoscopy\nAcknowledgements\nNot applicable.\nAuthor contributions\nACK: contributed to the conception and design of the case report. ACK, SA: \ncollection of data, Revision of the manuscript, preparing figures and perform-\ning the last evaluation. All the authors read and approved the final manuscript.\nFunding\nNot applicable.\nAvailability of data and materials\nNot applicable.\nTable 2 Literature review of knot formation\nDJ double J, ESWL extracorporeal shock wave lithotripsy, PCN percutaneous nephrostomy, URS Ureterorenoscopy\nCase Year Author Age/Gender Location Technique of removal\n1 1989 Groeneveld et al. [1] NA Proximal Gentle traction\n2 1990 Das et al. [9] 45/M Distal Gentle traction\n3 1992 Braslis et al. [10] 37/F Proximal Percutaneous nephrostomy (PCN) removal\n4 1994 Kundagi et al. [11] 53/M Proximal PCN removal\n5 1995 Flam et al. [7] 86/M Proximal 2nd DJ stent and URS\n6 1998 Baldwinn et al. [6] 73/M Proximal Guidewire (Superstiff ) to untie the knot\n7 2002 Quek M et al. [12] 66/F Mid Gentle traction\n8 2005 Sighinolfi et al. [4] 48/M Proximal Continuous traction for 3 days and ESWL\n9 2005 Kondo et al. [13] 37/M Proximal Ureterotomy\n10 2006 Eisner et al. [5] 82/F Proximal Gentle traction (Valsalva)\n11 2007 Basavaraj et al. [14] 70/F Proximal PCN and gentle traction\n12 2009 Rivalta et al. [15] 83/M Proximal Gentle traction with vaseline lubrication\n13 2010 Picozzi et al. [16] 41/F Proximal Gentle traction\n14 2011 Tempest et al. [17] NA Proximal URS and Holmium laser\n15 2011 Richards et al. [18] 67/M Proximal URS and Holmium laser\n16 2012 Moufid et al. [19] 32/M Proximal 2nd DJ stent and gentle traction\n17 2012 Karaguzel et al. [20] 53/M Proximal URS and gentle traction\n18 2012 Nettle et al. [21] 43/M Proximal URS and Holmium laser\n19 2012 Bhirud et al. [22] 41/M Proximal Percutaneous removal with 26F nephroscope\n20 2015 Ahmadi et al. [8] 45/M Proximal URS and Holmium laser\n21 2015 Ahmadi et al 43/M Proximal URS and Holmium laser\n22 2015 Ahmadi et al 71/M Proximal URS and percutaneous retrieval at later date\n23 2015 Ahmadi et al 55/M Proximal URS and Holmium laser\n24 2015 Kim et al. [23] 53/M Proximal Percutaneous and Terumo Guidewire\n25 2015 Manohar et al. [24] 65/M Proximal Staged percutaneous antegrade removal\n26 2015 Manohar et al. 65/F Proximal URS and Holmium laser\n27 2015 Manohar et al. 55/F Proximal URS and Holmium laser\n28 2015 Manohar et al. 59/M Proximal Gentle traction\n29 2020 Bradshaw et al. [3] 57/F Proximal URS and dilation\n30 2020 Cho et al. [25] 62/M Proximal URS and guidewire\n31 2021 Choo ZW et al. [26] 73/M Proximal URS and Holmium laser\n32 2022 Agarwal et al. [27] 77/M Proximal Access sheath assembly\n33 2022 Agarwal et al 44/M Proximal Access sheath assembly\n34 2022 Agarwal et al 65/M Proximal Access sheath assembly\n35 2022 Gur et al. [28] 25/F Mid Guidewire\n36 2022 Jendouzi et al. [2] 20/M Proximal URS and Holmium laser\n37 2022 Divya et al. [29] 5/M Proximal Percutaneous and cystoscopically\n38 2023 Weeratunga et al. [30] 73/M Proximal Loop-snare technique\n39 2023 Present study 67/M Proximal Gentle traction\n40 2023 Present study 35/M Proximal Gentle traction\n\nPage 7 of 7\nKolu and Akan  Journal of Medical Case Reports          (2024) 18:103 \n \nDeclarations\nEthical approval and consent to participate\nNot applicable.\nConsent for publication\nWritten informed consent was obtained from the patients for publication of \nthis case report and any accompanying images. A copy of the written consent \nis available for review by the Editor-in-Chief of this journal.\nCompeting interests\nThe authors declare that they have no competing interests.\nReceived: 19 December 2023   Accepted: 19 January 2024\nReferences\n 1. Groeneveld AE. The role of ESWL in the treatment of large kidney stones. \nSingap Med J. 1989;30(3):249–54.\n 2. Jendouzi O, Lamghari A, Jamali M, Harchaoui A, Alami M, Ameur A. Knot-\nted double J ureteral stent: a case report and literature review. 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