Retained Biliary Plastic Stents: Clinical Presentation, Complications, and Management

Background Biliary plastic stent (PS) mandates timely removal or replacement. The coronavirus disease 2019 (COVID-19) pandemic had affected the accessibility to medical therapy resulting in delay. We evaluated the burden of retained biliary PS, clinical pro ﬁ le, and impact of COVID-19 pandemic on stent retention. Material and Method Endoscopy database records between November 2019 and April 2022 were reviewed retrospectively to identify patients who had undergone stent exchange or removal > 3 months, that is, retained stents. Demography, comorbidity, indication and outcomes of index endoscopic retrograde cholangiopancreatography, size and duration of indwelling biliary PS, clinical presentation, imaging ﬁ ndings, cholangiography ﬁ ndings, stent-related complications, and stone formation and endotherapy details were noted. Results A total of 252 patients (100 [39.68%] males; median age 47 years [inter-quartile range [IQR] 32 – 56 years]) had common bile duct (CBD) stent retention. Median duration


Introduction
Biliary plastic stents (PSs) are tubular devices which are placed in the bile duct to maintain patency for flow of bile.Among various indications, they are often used for shorter duration followed by removal whereas longer duration placement needs periodic replacement. 1 The complications associated with long-term use includes stent block, cholangitis, stent migration, stentolith formation, and rarely perforation. 2,3Hence, it is recommended to replace or remove biliary PSs every 3 months to prevent these complications. 1 However, there is limited data regarding natural history of biliary stents beyond 3 months.Jaleel et al assessed 45 patients with retained biliary stents longer than 3 months and noticed that majority were asymptomatic with acute cholangitis in 9, choledocholithiasis in 2, and cholangitic abscess in 1 case. 4Sohn et al evaluated 38 patients with biliary stent left for more than 12 months and found acute cholangitis in 36 (94.7%) cases and stones and sludge in 35 (92.1%) cases. 5In a case series of 48 patients with plastic biliary stents retained for > 12 months, by Duman et al, the most frequent complications were stone formation (79%) and proximal stent migration (26.4%). 6The coronavirus disease 2019 (COVID-19) pandemic exposed us to this scenario where due to delay in elective surgeries and stent exchanges a lot of patients presented with retained stents.Hence, we conducted an audit to study the clinical presentation, complications, and outcome of patients with retained common bile duct (CBD) stents.

Material and Methods
Data collection was started after ethics committee approval (Project no.EC/OA-125/2022).
Patients: We analyzed prospectively maintained endoscopy database from November 2019 to April 2022 to identify patients who had undergone endoscopic retrograde cholangiopancreatography (ERCP) procedures for biliary indications.All patients with retained CBD PS were included in the study.Retained CBD stent was defined as indwelling PS for more than 3 months from the date of placement.All patients with selfexpandable metal stents (SEMS), indwelling PSs in SEMS, and externally migrated stents were excluded from study.Demography, comorbidity, indication, and outcomes of index ERCP, size and duration of indwelling biliary PS, clinical presentation, imaging findings, ERCP findings and retrieval or exchange of stent, stent-related complications, and stone formation were noted.Stent-related complications were defined as those related to stent dysfunction like jaundice, abdominal pain, cholangitis, cholangitic abscess, or related to structural integrity like fragmentation or internal migration.The reason for delay in stent exchange or removal due to COVID-19 pandemic or other causes were noted separately.
Endoscopy procedure: All ERCP procedures were performed by experienced operators with more than 500 successful ERCPs and capable of performing grade 3 ERCP.In patients with cholelithiasis and choledocholithiasis with previous complete CBD clearance stent was removed, and balloon sweeps and occlusion cholangiogram were taken to confirm CBD clearance but stent was not placed.Patients with incomplete CBD clearance with or without cholecystectomy, CBD clearance was performed.If successful, stent was placed only in those patients awaiting cholecystectomy.In all patients with incomplete CBD clearance, PS was placed.In patients with benign and malignant biliary strictures, stent exchange was performed.Straight biliary PSs of various sizes were used (Cook Medical, Bloomington, Indiana, United States).In patients with internal migration double pigtail PS was used after extraction of migrated stent.
Procedure was performed under total intravenous anaesthesia or general anaesthesia with TJF Q180V duodenoscope (Olympus, Tokyo, Japan).Previously placed stents if visualized at the papilla, were retrieved using snare (Cook Medical) or grasping forceps (rat tooth alligator jaw grasping forceps, Olympus).All internally migrated stents were retrieved using standard techniques.Details about stent fragmentation, stentolith, and presence of CBD calculi were documented.Further stone extraction, stricture dilation, and stent replacement was done according to standard treatment protocol.
Outcome measures: Prevalence of retained CBD stent, clinical presentation, and complications associated with it.Impact of COVID-19 pandemic on prevalence of retained CBD stents and its complications.
Data collection and statistical analysis: Data was collected and analyzed using SPSS version 24 (IBM Corporation, Armonk, New York, United States).Quantitative variables were represented using mean, median, and standard deviation.Qualitative variables in proportions were compared using chi-square test or Fisher's exact test.Univariate and multivariate logistic regression was performed to determine predictors of complications (obstructive jaundice, cholangitis and cholangitic abscess, stent migration, and fragmentation).

Results
In the study period (November 2019-April 2022), 2,937 ERCP were performed for biliary indications.After reviewing medical Conclusion CBD PS stent retention, although mostly asymptomatic, can result in significant morbidity like jaundice, cholangitis, stent migration, fragmentation, or impaction in one-fourth of patients.Use of 7 Fr stent, retention duration > 6 months, abnormal imaging findings, and AST > twice the upper limit were significantly associated with complications.Endoscopic management was successful in 97% of patients.
records 252 (8.47%) patients with retained CBD stents were identified and included in the study.Out of 252, 71 (28.2%) index procedures were performed elsewhere and patients presented to us for retained CBD stent management.
All patients with retained stent underwent ERCP with either removal or replacement of previously placed stent.After removal of previously placed stent, CBD stones were noted in 67/252 (26.6%) (54 patients with new onset CBD stones, 13 patients with index incomplete CBD clearance) cases while sludge was noted in 41/252 (16.26%) cases.Indwelling stent for > 6 months was associated with significantly increased risk of stone formation, 58/72 (80.5%) versus 9/180 (5%), p ¼ 0.0049.Complete bile duct clearance was achieved in 105/108 (97.22%) patients with standard accessories.Three patient with large stone further required cholangioscopy-guided electrohydraulic lithotripsy.Four (1.6%) patients had proximal stent migration in the biliary tree for which additional manipulation with balloon sweeps, rat tooth forceps, and Soehendra stent retriever was required to retrieve the stent.►Fig. 2 shows fluoroscopic image of internally migrated stent into left hepatic duct.Stent fragmentation was noted in 20/252 (8%) cases.Fragmented stent were pulled out of the bile duct using stone extraction balloon and removed using snares or rat tooth forceps.►Fig.3 shows image of a fragmented biliary PS being removed with rat tooth forces.In three cases fragment of the stent got impacted in the biliary tree requiring successive cholangioscopy-guided removal.So, overall technical success   for retained CBD stent retrieval and complete clearance of calculi and sludge was achieved in 97.6% (246/252) with one session of ERCP, while 2.38% (6/252) required second session with cholangioscopy-guided clearance.Indwelling PS for more than 6-month duration was associated with stent fragmentation (< 6 vs. > 6 months ¼ 0 vs. 20, p 0.005).In patients with benign strictures (n ¼ 52) stent exchange was performed with higher caliber stent or multiple stents were placed with 100% technical success.In patients with malignant biliary obstruction (n ¼ 47), PS exchange was done in 40 (85.1%)cases whereas replacement with SEMS was done in 8 cases due to disease progression and metastasis.In all patients with bile leak (n ¼ 9) stent was removed as leak was healed and there was no stricture on cholangiogram.All patients (n ¼ 38) with portal cavernoma cholangiopathy without shuntable vessel underwent clearance of bile duct of stone or sludge with replacement of stent.During initial analysis of records, a total of 9 patients were found to have external migration of the stent (3-to 6-month group ).As the stents were expelled, and not retained in the CBD, these patients were not included in the analysis.
On univariate logistic regression analysis, serum aspartate aminotransferase (AST) levels, serum alkaline phosphatase levels, and presentation beyond 6 months of index ERCP were significantly associated with complications.On multivariate logistic regression analysis serum AST levels > 2 upper normal limit (odds ratio [OR] 5.487, 95% confidence interval [CI] ¼ 3.1-9.9,p 0.005) and interval between primary ERCP and stent exchange or removal of > 6 months (OR ¼ 8.6, CI ¼ 3.1-23.92,p 0.005) were significantly associated with complications.
Impact of COVID-19 pandemic on scheduled stent exchange or removal: COVID-19 pandemic resulted in significant disruption of scheduled appointments for stent exchange or stent removals.In our series, 101 (40.07%) patients had delay in presentation to hospital due to delayed appointments (34 patients), inability to reach hospital (43 patients) due to nationwide lockdown, and 24 patients did not report due to anxiety of acquiring COVID-19 infection if they leave home.Out of 101 patient with delayed stent exchange or removal during the COVID-19 pandemic, 56 had symptoms related to stent dysfunction (abdominal pain 26, cholangitis 24, cholangitic abscesses 4, stent migration 2) and presented to the hospital.During COVID-19 pandemic 30/101 (29.70%) patients had delay of more than 6 months for stent exchange or removal while 38/151 (25.1%) had delay of more than 6 months during non-COVID days (p ¼ 0.092).Although difference was near statistical significance we feel this delay could be the reason for the same.

Discussion
Biliary PS provide a measure of biliary drainage but these endoprostheses need removal or exchange after 3 months of insertion. 1A longer duration is usually associated with common complications like stent block and migration while bleeding, duodenal perforation, and cholecystitis are rare.Stent block occurs due to accumulation of sludge and/or bacterial biofilm. 7In addition to microbial colonization, duodenal reflux of food constituents (e.g., fibers) and several other factors have been suggested to be involved in the occlusion of these endoprostheses.These factors include stent design, physiochemical properties of the constitutive materials, surface irregularities of the devices promoting microbial biofilm formation, and biliary sludge accumulation. 8he durations of CBD PS retention in various studies by Chandra and colleagues, Sohn et al, and Jaleel et al was 3.53 years (range 1-14 years), 22.6 AE 12.8 months, and 144 days (94-3,929 days), respectively. 4,5,91][12][13][14] In our study, the median duration of stent retention was 5 months (IQR ¼ 4-6 months).Kumar et al and Sohn et al reported cholangitis as the most common presentation when stent retention was more than 12 months, while Jaleel et al found majority (68.9%) were asymptomatic when stents were retained > 3 months. 4,5,96][17] Reported mortality in patients with stent-related cholangitis is as high as 6.7% in long-term biliary stenting for choledocholithiasis. 15 In our study, the majority 182 (72.2%) were asymptomatic but 22 (8.7%) had cholangitis and 16 (6.3%)had only jaundice, while 32 (12.7%) had biliary abdominal pain.There were no mortality associated with cholangitis and other complications.In the study by Sohn et al internal migration of stent was seen in 3 (10.7 %) in the 1-to 2-year stent retention group and in 2 (20%) in the > 2 year stent retention group. 5In our study, stent structural integrityrelated complications, that is, stent migration and stent fragmentation, were seen in 4 (1.6%) and 20 (8%) patients, respectively, and retention duration > 6 months was significantly associated with stent fragmentation and choledocholithiasis.
The biliary stent itself may serve as a nidus for stone formation, hence increases the risk of formation of biliary stones. 18Sohn et al reported that 35/38 patients with CBD stent retention > 12 months developed CBD stone or sludge even when the primary indication of stenting was for biliary stricture without CBD stone. 5All stones observed in the above study were brown pigment stones, thus implying the role of ascending infection.In the study by Kaneko et al, regarding stone-stent complex (SSC), it was found that duration of more 301 days and increase in CBD diameter during the period of PS placement is a predictive factor for SSC formation in this situation. 19In our study, stone formation were seen in 67 (26.6%) cases which was significantly associated with stent retention duration of > 6 months.
Multivariate logistic regression analysis showed that serum AST levels > 2 upper normal limit and interval between primary ERCP and stent exchange or removal of > 6 months were significantly associated with complications.Hence, abnormalities in liver function test (AST) and stent retention duration > 6 months were associated with symptomatic cases and complications related to stent retention.
The effect of COVID-19 pandemic for CBD stent retention was seen, as 101 (40.07%) patients had a delay in their scheduled stent exchange due to various reasons during COVID-19 pandemic.Out of these patients, 56 were symptomatic (55.44%).However, there was no statistically significant effect of COVID-19 pandemic on symptomatology or complications.In the study by Freitas et al regarding CBD PS exchange of 120 patients in COVID-19 pandemic, there were no differences in clinical presentation and complication between the delayed (> 6 months) versus early removal (< 3.5) group. 20ll the patients in our study were managed medically and endoscopically with technical success rate of 96.66%, failures being due to large stone (n ¼ 3) and impacted stents (n ¼ 3) in whom technical success could be achieved in another session with cholangioscopy.Similarly, in the study by Jaleel et al, all patients were managed medically and endoscopically (18/45 patients required further sessions) while Kumar et al reported definitive endoscopic treatment only in 5 patients (23.8%) and necessity of surgical exploration in remaining 16 (76.2%)cases. 4,9Sohn et al reported successful endoscopic management of retained CBD stent in 35 of 38 patients (92.1%). 5While most studies have reported > 90% success with endoscopic measure, Chandra and colleagues had lower success which can be attributed to selection and referral bias from a surgical center, lack of technical expertise, and access to various newer accessories and cholangioscopy.
Various limitations of the study are retrospective cohort, single-center study, and the COVID-19 infection as a confounding factor with its unknown effect on liver and bile lithogenicity.The communication to patient regarding nature of the disease and stressing on complications of delayed follow-up is very important.This can further be strengthened by setting up reminder system in the endoscopy unit for calling patients for follow-up.A separate team and electronic reminder system can be set up in the endoscopy unit for the same.Further studies would need to be done to derive more exact cutoff times.

Conclusion
Retained biliary PS although mostly asymptomatic can result in significant morbidity like jaundice, cholangitis, stent migration, fragmentation, or impaction in one-fourth of patients.Use of 7 Fr stent, retention duration > 6 months, abnormal imaging findings, and AST > twice the upper limit were significantly associated with complications.COVID-19 pandemic caused a delay in stent exchange in one-third patients without any significant effect on symptomatology or complications.All patients were managed endoscopically with a technical success rate of 97%, without any mortality.

Fig. 1
Fig. 1 Computed tomography image showing dilated biliary radical (red arrow) with plastic stent in situ (blue arrow) and cholangitic abscess (black arrow).

Fig. 2
Fig. 2 Fluoroscopic image of internally migrated plastic stent in left hepatic duct (black arrow).

Fig. 3
Fig.3Fragmented biliary plastic stent being removed with rat tooth forces.

Table 1
Demographic characteristics and laboratory investigations