Spontaneous knot formation complication of double J: two case reports

Background Use of ureteral stents has become an integral part of urological practice. However, it also brought with it many complications. Double J (DJ) stent knotting is a rare stent complication, and only a few cases have been reported in the literature. Although the exact cause is unknown and, in the literature, it is generally thought that knots occur due to traction. In this case report we present for the first time that spontaneous knots can occur due to ure- teral peristalsis or ureteral anomalies. Case presentation Two patients (67 and 35 aged-Caucasian person) with ureteral stones who presented to the emergency department with colicky pain and had no previous history of urological surgery. We observed knot formation in the routine urinary system radiographs taken before stent removal in two patients whose ureters were observed to be narrow during endoscopic ureteral stone treatment. The stents were successfully removed using gen- tle traction under general anesthesia.

We discussed the cause and solution of spontaneous knot formation. We emphasized the importance of the direct urinary system radiograph taken before DJ stent removal.

Knotted ureteral stent, Urological complication, Ureteral stent

The ureteral stents, which become an integral part of modern urological practice, provide urinary tract access, dilation of urinary strictures, removal of kidney stones, and temporary drainage of urine. There are various size (14–32 cm), diameter (3–8 F), hardness, body, tip shapes (pigtail, double pigtail-JJ) and coating (carbon, hydro - philic, heparin) ingredients for the purpose of use. During their time with ureteral stents, 80% of patients report experiencing some degree of discomfort. Addi - tionally, the use of ureteral stents may lead to serious complications such as stent migration and stent encrusta- tion. Although spontaneous knotting of the ureteral stent has been reported before, it is one of the rare complica - tions in the literature. There are a variety of techniques reported for the removal of a knotted double J (DJ) stent, from simple traction to open surgery. Case report The first case, a 67-year-old man (Caucasian), applied to our clinic with a complaint of left side pain that had been going on for a month. On physical examination, positive left costovertebral angle (CVA) tenderness was observed (Table  1). He had hypertension and diabe - tes. There was a stone disease in his father. The patient had no previous history of renal colic, urinary system stone disease or any surgical intervention. In the imag - ing performed for the patient, “Grade 2 ectasia in the upper collecting system of the left kidney, double ure - ter appearance on the left and suspicious stone image at the level of the left iliac crossover” was observed; ureterorenoscopy (URS) was planned for the patient. *Correspondence: Ahmet Can Kolu [email protected] 1 Department of Urology, University of Health Sciences, Fatih Sultan Mehmet Research & Training Hospital, 34758 Istanbul, Turkey Page 2 of 7Kolu and Akan Journal of Medical Case Reports (2024) 18:103 During cystoscopy, a close monitoring of the patient’s left ureteral orifice revealed an attempt to insert a sen - sor guide. However, it failed to transition from the mid - dle ureter to the proximity. Then, the distal ureter was entered through the left ureteral orifice by applying ureteral balloon dilation under the guidance of a sensor guide. The ureter at the iliac cross level was passed with difficulty, but due to stenosis, it could not be advanced further proximally; 4.8 Fr 26  cm DJ was placed and it was seen that both ends were bent under fluoroscopy. The second case (Caucasian), aged 35, had complaints of right-side pain for four months. On physical exami - nation, positive right CVA tenderness was observed (Table  1). The patient had no comorbidity. There was a stone disease in his family. A calculus of 3–4  mm in size was observed in the right distal ureter in the imag - ing performed on the patient, who had a previous his - tory of passing spontaneous urinary system stones but did not have a previous surgical history. During the URS procedure performed 2 weeks later, annular stenosis was observed 2  cm ahead of the right orifice and was cor - rected with balloon dilatation. Endoscopic ureteral stone treatment was performed with holmium laser. At the end of the surgery, a 4.8 Fr 26 cm DJ was placed into the right ureter and the procedure was terminated. No periop - erative or postoperative complications were observed in both cases, and the urinary system was visualized on the radiography on the first day after the operation (Fig.  1A, B). In both cases, when the urinary system radiographs were repeated six weeks later for routine DJ stent removal; spontaneous knotting was observed at the prox- imal end of the DJ stents (Fig.  2A, B). Both of patients no bothersome symptoms were reported, and the physical examination was strictly normal. Considering the possi - bility that the procedure could be complicated, DJ stent removal was planned under general anesthesia. After the distal coil of the DJ stents was corrected, gentle trac - tion was applied toward the contralateral bladder wall. DJ stents were barely removed without complications, and proximal ends were found to be coming in knotted (Fig. 3A, B). A 7Fr ureteral catheter was placed over the guide wire to the renal pelvis. The ureteral catheter was removed on postoperative day 1; After observation, the patient was discharged with nonsteroidal anti-inflamma - tory drug (NSAII) and antibiotic treatment.

Ureteral DJ stent complications include irritative mictu - rition symptoms, suprapubic pain, costovertebral pain, vesicorenal reflux, stent malposition, hematuria, uri - nary tract infection, fever, encrustation, stent migration, stent rupture, ureteral perforation, erosion and fistuliza - tion. To our best knowledge, only a few cases have been identified in the literature since Groeneveld et  al. first reported it in 1989 [1]. Table  2 summarized the previ - ously recent published cases regarding DJ stent knot - ting. Knotted formation is a rare complication, with only 40 cases being described and can be vexing to manage. In the vast majority of reported cases (92.5%), knotting was observed at the proximal end of the DJ stent. In our patients and in the majority of other cases of knotting, the patients were asymptomatic and the cases typically presented with unexpected resistance during DJ stent removal. In the majority of reported cases, no abnormal appear - ance was detected in the urinary system radiograph taken before stent removal [2], which would suggest knotting in the DJ stent; it has been stated that the knot may form due to traction during extraction. However, in our cases, knot formation was observed to develop spontaneously immediately after URS, without any intervention or trac - tion. This suggests that knot formation may develop due to the ureter’s own peristalsis or secondary to balloon dilatation applied to the abnormal ureter. In approximately one-third of reported cases, the DJ stent could be removed with gentle traction and the con - dition was treated successfully [3]. However, this proce - dure carries risks for these patients as it may make the existing knot tighter and increase the degree of compli - cations. If strong resistance is encountered during DJ stent removal, alternative interventions should be con - sidered to avoid causing serious ureteral trauma or loss of renal function [3]. In previous years, “the use of ster - ile Vaseline in addition to traction” has been tried; There Table 1 Timeline Time intervals are the same for both patients URS Ureterorenoscopy Time (t) t0 t1 t2 t3 Important dates Initial presentation After 2 weeks (URS time) 1 day after URS 6 weeks after URS Page 3 of 7 Kolu and Akan Journal of Medical Case Reports (2024) 18:103 are suggestions such as “securing the distal end of the DJ catheter to the leg with a catheter band and providing continuous traction for 3 days” or “applying extracorpor- eal shock wave lithotripsy (ESWL) to the migrated area of the knotted stent” [4]. In another case where knot formation was observed twice in the same patient, no additional intervention was required to open the second knot formation; spon - taneous resolution of the node has been associated with the Valsalva effect achieved by recurrent severe coughs [5]. Valsalva has been suggested as an easy and harm - less treatment before invasive procedures for removing knotted stents. Baldwin et al. used an “ Amplatz 0.038 super stiff guide- wire” at the proximal end of the stent to solve knot for - mation [6]. Flam et  al. placed a second ureteral stent next to the knotted stent, and a week later, the stent was removed with 5Fr alligator forceps [7]. Endourologically, breaking down the knot formation with a holmium laser and removing the stent has been suggested in the litera - ture as another method [8]. Removal of knot-forming stents via percutaneous or open surgery should only be performed after failure with other techniques. Urologists should be aware of the possibility of knot formation in the stent if difficulty is encountered during stent removal. Fig. 1 A Case 1 direct urinary system graphic after Ureterorenoscopy. B Case 2 direct urinary system graphic after Ureterorenoscopy Page 4 of 7Kolu and Akan Journal of Medical Case Reports (2024) 18:103

Although the literature shows that a knot can occur with traction during DJ stent removal, we also believe that a spontaneous node may be caused by ureteral peristalsis or ureteral anomalies. Therefore, the routine use of a uri- nary system graph (X) for all patients before the release of the DJ stent can prevent potential complications due to spontaneous knot formation. Even if we do not see knot formation on the x-ray, in all cases with ureteral stent in which difficulty is experienced during removal, the possibility of stent knotting should always be kept in mind and therapy planned accordingly. Fig. 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 Page 5 of 7 Kolu and Akan Journal of Medical Case Reports (2024) 18:103 Fig. 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 Page 6 of 7Kolu and Akan Journal of Medical Case Reports (2024) 18:103 Abbreviations CVA Costovertebral angle DJ Double J ESWL Extracorporeal shock wave lithotripsy NSAII Nonsteroidal anti-inflammatory drug PCN Percutaneous nephrostomy URS Ureterorenoscopy

Not applicable. Author contributions ACK: contributed to the conception and design of the case report. ACK, SA: collection of data, Revision of the manuscript, preparing figures and perform- ing the last evaluation. All the authors read and approved the final manuscript. Funding Not applicable. Availability of data and materials Not applicable. Table 2 Literature review of knot formation DJ double J, ESWL extracorporeal shock wave lithotripsy, PCN percutaneous nephrostomy, URS Ureterorenoscopy Case Year Author Age/Gender Location Technique of removal 1 1989 Groeneveld et al. [1] NA Proximal Gentle traction 2 1990 Das et al. [9] 45/M Distal Gentle traction 3 1992 Braslis et al. [10] 37/F Proximal Percutaneous nephrostomy (PCN) removal 4 1994 Kundagi et al. [11] 53/M Proximal PCN removal 5 1995 Flam et al. [7] 86/M Proximal 2nd DJ stent and URS 6 1998 Baldwinn et al. [6] 73/M Proximal Guidewire (Superstiff ) to untie the knot 7 2002 Quek M et al. [12] 66/F Mid Gentle traction 8 2005 Sighinolfi et al. [4] 48/M Proximal Continuous traction for 3 days and ESWL 9 2005 Kondo et al. [13] 37/M Proximal Ureterotomy 10 2006 Eisner et al. [5] 82/F Proximal Gentle traction (Valsalva) 11 2007 Basavaraj et al. [14] 70/F Proximal PCN and gentle traction 12 2009 Rivalta et al. [15] 83/M Proximal Gentle traction with vaseline lubrication 13 2010 Picozzi et al. [16] 41/F Proximal Gentle traction 14 2011 Tempest et al. [17] NA Proximal URS and Holmium laser 15 2011 Richards et al. [18] 67/M Proximal URS and Holmium laser 16 2012 Moufid et al. [19] 32/M Proximal 2nd DJ stent and gentle traction 17 2012 Karaguzel et al. [20] 53/M Proximal URS and gentle traction 18 2012 Nettle et al. [21] 43/M Proximal URS and Holmium laser 19 2012 Bhirud et al. [22] 41/M Proximal Percutaneous removal with 26F nephroscope 20 2015 Ahmadi et al. [8] 45/M Proximal URS and Holmium laser 21 2015 Ahmadi et al 43/M Proximal URS and Holmium laser 22 2015 Ahmadi et al 71/M Proximal URS and percutaneous retrieval at later date 23 2015 Ahmadi et al 55/M Proximal URS and Holmium laser 24 2015 Kim et al. [23] 53/M Proximal Percutaneous and Terumo Guidewire 25 2015 Manohar et al. [24] 65/M Proximal Staged percutaneous antegrade removal 26 2015 Manohar et al. 65/F Proximal URS and Holmium laser 27 2015 Manohar et al. 55/F Proximal URS and Holmium laser 28 2015 Manohar et al. 59/M Proximal Gentle traction 29 2020 Bradshaw et al. [3] 57/F Proximal URS and dilation 30 2020 Cho et al. [25] 62/M Proximal URS and guidewire 31 2021 Choo ZW et al. [26] 73/M Proximal URS and Holmium laser 32 2022 Agarwal et al. [27] 77/M Proximal Access sheath assembly 33 2022 Agarwal et al 44/M Proximal Access sheath assembly 34 2022 Agarwal et al 65/M Proximal Access sheath assembly 35 2022 Gur et al. [28] 25/F Mid Guidewire 36 2022 Jendouzi et al. [2] 20/M Proximal URS and Holmium laser 37 2022 Divya et al. [29] 5/M Proximal Percutaneous and cystoscopically 38 2023 Weeratunga et al. [30] 73/M Proximal Loop-snare technique 39 2023 Present study 67/M Proximal Gentle traction 40 2023 Present study 35/M Proximal Gentle traction Page 7 of 7 Kolu and Akan Journal of Medical Case Reports (2024) 18:103 Declarations Ethical approval and consent to participate Not applicable. Consent for publication Written informed consent was obtained from the patients for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal. Competing interests The authors declare that they have no competing interests. Received: 19 December 2023 Accepted: 19 January 2024

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