Successful redrainage after failure of lumen-apposing metal stents by addressing flange-induced ostial occlusion: A case report

Abstract

BACKGROUND

Endoscopic ultrasound-guided drainage is the standard treatment for symptomatic walled-off necrosis (WON). Lumen-apposing metal stents (LAMSs) revolutionize this approach using large lumens and stable flanges, enabling efficient drainage and direct necrosectomy. While established complications (intraluminal occlusion, and migration) are well-documented, LAMS flange-complex WON anatomy interaction remains unclear. Up to date, no cases of the distal flange causing mechanical occlusion of branch cavity ostia have been reported. This case addresses this complication and its successful endoscopic management.

CASE SUMMARY

We report a 34-year-old man with recurrent WON caused by LAMS edge-induced branch cavity ostium obstruction, managed via endoscopic LAMS removal and salvage plastic stent drainage. Admitted for biliary pancreatitis complicated by cholangitis, he underwent endoscopic stone extraction and biliary stenting. Postoperative fever prompted abdominal computed tomography (CT), which revealed peripancreatic collections consistent with WON; endoscopic ultrasound-guided transgastric LAMS placement achieved immediate purulent drainage. Endoscopic necrosectomy resolved fever, and follow-up CT/endoscopy confirmed near-complete cavity collapse before discharge. Five days later, recurrent high fever led to repeat CT, showing pancreatic body reaccumulation. Endoscopy indicated branch ostium obstruction by the LAMS distal flange. LAMS removal identified a purulent fistula, and fluoroscopy-guided stenting with a double-pigtail stent and nasobiliary tube achieved prompt resolution. The nasobiliary tube was removed prior to discharge, with the pigtail stent retained for spontaneous passage.

CONCLUSION

LAMS edge obstruction of branch ostia can cause recurrent WON. Endoscopic removal plus cavity inspection and drainage is effective.

Key Words: Lumen-apposing metal stent; Walled-off necrosis; Endoscopic ultrasound; Complication; Salvage drainage; Case report

Core Tip: This case report describes a rare complication of recurrent walled-off necrosis caused by mechanical occlusion of a branch cavity ostium by the edge of a lumen-apposing metal stent. This was successfully managed by endoscopic removal of the lumen-apposing metal stent, followed by salvage drainage with plastic stents, resulting in complete resolution of symptoms and radiographic findings. The case highlights a novel failure mechanism that underscores the importance of precise stent positioning and the effectiveness of this endoscopic salvage approach.

INTRODUCTION

Management of pancreatic fluid collections, particularly walled-off necrosis (WON), has been radically transformed by the advent of endoscopic ultrasound (EUS)-guided drainage[1,2]. WON, a common sequela of severe acute pancreatitis, is characterized by a well-defined inflammatory capsule enclosing pancreatic and peripancreatic necrotic tissue. Its management is challenging due to the potential for infection, mass effect, and persistent systemic illness[3]. While symptomatic or infected WON historically required surgical or percutaneous intervention, endoscopic transmural drainage has emerged as the first line, minimally invasive method, significantly reducing patient morbidity and hospital stay compared to traditional approaches[4].

The introduction of lumen-apposing metal stents (LAMSs) marked a significant improvement over conventional plastic stents[5]. Specifically designed for cystenterostomy, LAMSs feature a wide, saddle-shaped design with bilateral anchoring flanges that appose the gut and cavity walls[6]. This design facilitates a stable, large-caliber conduit (typically 10-20 mm), enabling direct endoscopic necrosectomy for evacuation of solid debris and significantly reducing the procedure time and need for repeated interventions[6]. Multiple studies and meta-analyses have established the superior clinical success and efficiency of LAMSs for WON drainage[7].

However, the widespread adoption of LAMSs has revealed a distinct profile of device-specific complications. Current literature predominantly focuses on stent lumen occlusion by necrotic debris, stent migration, bleeding, and de novo infection[8-10]. International consensus guidelines have been updated to categorize and manage these known adverse events[11]. Despite this, a critical knowledge gap persists regarding complications arising from the physical interaction between the LAMS structure and the complex anatomy of WON itself[12]. A significant proportion of WON collections are multilocular or feature secondary extensions[13]. The current paradigm for LAMS placement involves creating a single, central cystenterostomy[14]. It remains unexplored in the literature how the distal flange of a LAMS might mechanically interact with and potentially occlude the ostia of such satellite cavities or branches, leading to a unique form of drainage failure that is not attributable to intraluminal blockage. This case report describes the first documented instance of this novel complication and its successful endoscopic management.

CASE PRESENTATION

Chief complaints

A 34-year-old man presented with a 19-day history of abdominal pain and a 3-day history of fever.

History of present illness

Nineteen days ago, the patient experienced unexplained persistent colicky periumbilical pain accompanied by nausea and vomiting. The vomitus consisted of gastric contents, with no relief of abdominal pain after vomiting. The patient also reported abdominal distension and radiating back pain. Abdominal computed tomography (CT) scan performed that day indicated: Pancreatitis with peripancreatic exudation, heterogeneous pancreatic density, and intra- and extrahepatic bile duct dilation. The patient subsequently received symptomatic supportive treatment at an external hospital, without significant improvement. Fourteen days ago, the patient was discharged and presented to the gastroenterology department of our hospital for further management. Laboratory tests upon admission revealed markedly elevated white blood cell count, total bilirubin, and amylase levels. Repeat abdominal CT demonstrated: Significant pancreatic swelling with multiple surrounding exudative collections, blurring of fat planes, suggestive of acute pancreatitis; dilated intra- and extrahepatic bile ducts; perihepatic fluid; and pelvic ascites. EUS confirmed acute pancreatitis and revealed choledocholithiasis with common bile duct dilation. Thirteen days ago, the patient underwent endoscopic retrograde cholangiopancreatography with stone extraction and placement of a biliary plastic stent. Following active treatment including antibiotic therapy and fluid resuscitation, the patient’s symptoms improved, and he was discharged eight days ago for recuperation. However, three days ago, the patient developed high fever (peak temperature 39.8 °C) accompanied by chills, rigors, nausea, and vomiting, although without significant abdominal pain or distension. He returned to our emergency department. Abdominal CT indicated: Markedly swollen pancreas with multiple peripancreatic exudative collections and thickening of bilateral renal anterior fascias, consistent with acute necrotizing pancreatitis with surrounding exudation, slightly worsened compared to prior imaging; and a biliary stent in the common bile duct and duodenum. The patient was subsequently admitted to the general surgery department with diagnosis of acute necrotizing pancreatitis and post-biliary stent placement.

History of past illness

The patient has a history of three previous episodes of pancreatitis in 2016, 2023, and 2024; each managed conservatively with good recovery. Cholecystectomy was performed in 2018.

Personal and family history

The patient reported no significant personal or family medical history.

Physical examination

The patient appeared fatigued with anicteric sclerae. His abdomen was soft and nontender, without rebound or guarding.

Laboratory examinations

The laboratory findings were as follows: White blood cell count 18.47 × 10⁹/L, neutrophil count 16.36 × 10⁹/L, neutrophil percentage 88.6%, serum amylase 275.1 U/L, total bilirubin 34.3 μmol/L, high-sensitivity C-reactive protein 110.93 mg/L, and procalcitonin 0.477 ng/mL.

Imaging examinations

Abdominal CT scan revealed: Significant pancreatic swelling with blurring of the fat planes. Thickening of the bilateral renal anterior fascias was noted, extending to the pancreaticoduodenal, gastrosplenic, perigastric, and left anterior pararenal spaces. Probable WON formation was observed in the pancreatic neck and body region, with involvement of the adjacent posterior splenic vein. The gallbladder was not visualized. Intra- and extrahepatic bile ducts were dilated, and a stent was identified within the common bile duct and duodenum (Figure 1).

Figure 1  Abdominal computed tomography demonstrating the formation of peripancreatic walled-off necrosis in a 34-year-old man.

FINAL DIAGNOSIS

Based on these findings, the patient was diagnosed with acute necrotizing pancreatitis, peripancreatic WON, status post biliary stent placement, and status post cholecystectomy.

TREATMENT

Initial transabdominal ultrasound assessment revealed no suitable percutaneous access, prompting a plan for endoscopic transmural drainage and debridement via the gastric route (Video). Using EUS, the endoscope was advanced into the stomach. Interrogation of the posterior wall of the mid-gastric body identified a hypoechoic area in the pancreatic neck and body. Doppler ultrasound confirmed the absence of vascular signals along the puncture trajectory; the gastric wall was punctured to access the collection; and an LAMS was deployed (Figure 2A). Successful stent placement was followed by immediate outflow of copious purulent material. On postoperative day 2, a gastroscope was used to remove all necrotic debris through the LAMS lumen using a retrieval net (Figure 2B). Direct visual inspection confirmed the cavity was largely clean, correlating with marked clinical improvement in the patient’s fever (Figure 2C). Follow-up abdominal CT and gastroscopy on postoperative day 4 demonstrated near-complete cavity closure, and the patient was discharged (Figure 3).

Figure 2 Endoscopic retrieval of necrotic debris via the lumen-apposing metal stents lumen. A: Abdominal computed tomography showing the lumen-apposing metal stents in good position and fully expanded; B: Endoscopic view using a retrieval net to extract necrotic debris; C: Visualization of the entire cavity after debris removal.

Figure 3 Significant reduction of the peripancreatic collection post-debridement. A-C: Abdominal computed tomography scans showing marked decrease in collection size; D: Endoscopic view confirming near-complete cavity closure.

Three days after discharge, the patient developed recurrent intermittent high-grade fever. Repeat abdominal CT showed a recurrent peripancreatic fluid collection at the pancreatic body (Figure 4). Endoscopy revealed that the LAMS cavity-side opening appeared sealed, raising suspicion for mechanical occlusion of a branch cavity ostium by the stent flange (Figure 5A). The LAMS was subsequently removed (Figure 5B). A small fistula with purulent discharge was identified at the left edge of the cavity (Figure 5C). A guidewire was inserted through the fistula, and fluoroscopy confirmed access to the recurrent collection. A 7F’ 5 cm double-pigtail stent and a 7F nasobiliary drainage tube were then placed (Figure 5D and E). The cavity was irrigated via the nasobiliary tube. The patient’s fever resolved promptly. Follow-up CT 2 days later showed near-complete resolution of the fluid collection (Figure 5F). The biliary stent and nasobiliary tube were removed endoscopically, while the double-pigtail stent passed spontaneously one month later.

Figure 4  Abdominal computed tomography revealing recurrent peripancreatic fluid collection.

Figure 5 Management of branch cavity ostium occlusion by lumen-apposing metal stents edge with plastic stents placement. A: Endoscopic view showing sealed lumen-apposing metal stents cavity-side opening; B: Lumen-apposing metal stents removal using a snare; C: Small fistula with purulent discharge at the 9 o’clock position of the cavity wall; D: Fluoroscopic confirmation of guidewires access into recurrent collection (arrow indicates guidewires); E: Fluoroscopic view showing nasobiliary drainage tube and double-pigtail stent placement (arrows indicate devices); F: Follow-up computed tomography demonstrating proper stents position and near-complete resolution of the collection.

OUTCOME AND FOLLOW-UP

At the 3-month follow-up after stent removal, the patient remained asymptomatic. Abdominal CT revealed normal pancreatic morphology and near-complete resolution of the prior collection (Figure 6).

Figure 6 Follow-up abdominal computed tomography at three months. Post-procedure showed slight pancreatic swelling with essentially normal morphology, and near-complete resolution of the cavity without recurrence.

DISCUSSION

Endoscopic management of symptomatic or infected pancreatic WON has been revolutionized by the advent of LAMSs[15,16]. LAMSs are primarily indicated for mature, symptomatic collections, typically exceeding 6 cm in diameter[17]. Compared to multiple plastic stents, their large-diameter lumen facilitates direct endoscopic necrosectomy, significantly reducing the need for repeated interventions and shortening hospital stay[18]. The literature reports technical success rates > 90% and clinical success rates between 80% and 95%[19,20]. Compared to percutaneous drainage, LAMSs establish a stable internal conduit, and against surgical or video-assisted retroperitoneal debridement, they offer a distinct minimally invasive advantage[21]. However, as their use expands, a deeper understanding of their unique complication profile is required.

This case presents the first detailed report of a novel LAMS complication: Localized recurrence of WON caused by mechanical occlusion of a branch cavity ostium by the distal stent flange. This finding reveals a previously under-recognized mechanism of failure distinct from the commonly reported issues of intraluminal debris obstruction, stent migration, or infection. The core of this mechanism lies in the obstruction occurring at the external edge of the stent structure rather than inside the lumen, and its target is the opening of a satellite or branch cavity. A systematic literature review confirmed no prior case or series describing this identical mechanism[18,22]. The most related reports discuss inadequate drainage due to suboptimal stent placement but do not elucidate the specific physical process of an ostium being directly covered and occluded by the stent flange[18,23].

The diagnostic process in this case highlights the challenge of identifying this complication. While CT imaging is sensitive in detecting recurrent localized fluid collection, it cannot determine the underlying cause[24]. More critically, the endoscopic observation of a sealed or closed appearance of the LAMS cavity-side opening is misleading. This can lead the endoscopist to mistakenly conclude that overall drainage has failed or that the cavity has healed, thereby overlooking the obstructed branch. Breaking this diagnostic impasse depended entirely on a proactive decision: To remove the LAMS and perform a systematic direct visual inspection of the cavity wall. The discovery of a minute fistula on the lateral cavity wall and the confirmation of its access to the recurrent collection via guidewire and fluoroscopy were the key diagnostic steps. This process emphasizes that for cases with isolated recurrent fluid after LAMS drainage and an endoscopically closed stent opening, flange-induced ostial occlusion should be highly suspected, and proactive stent removal for exploration should be actively considered.

Regarding treatment, LAMS removal was a necessary prerequisite to relieve the mechanical obstruction and expose the true drainage target. Subsequently, given the small size of the branch fistula and the preliminary establishment of a drainage tract, the placement of multiple double-pigtail plastic stents was a rational and effective salvage strategy. The appropriate diameter of plastic stents effectively maintains patency of the fistula, and their established clinical application minimizes technical risk. Compared to reinserting another LAMS, this strategy avoided the potential for reocclusion at the same site and may reduce cost and infection risk. The successful management in this case validates the safety and efficacy of the removal-inspection-targeted drainage salvage algorithm.

This finding carries important implications for clinical practice. First, it underscores the importance of meticulous planning during the initial treatment phase. For complex, multilocular, or highly septated WON suggested by pre-procedural imaging, the puncture site for EUS-guided LAMS placement must be chosen judiciously. The goal should be to deploy the stent so that its distal flange is in a central position capable of draining both the main cavity and major branch cavities, actively avoiding direct coverage of potential branch ostia by the flange. Second, during post-procedural follow-up, vigilance must be maintained for symptom recurrence or any new, isolated, or persistent fluid collections on imaging.

CONCLUSION

In summary, mechanical occlusion of a branch ostium by the LAMS flange is a noteworthy and likely under-estimated complication. Endoscopic stent removal with careful cavity inspection and subsequent targeted drainage of the identified obstructed branch constitutes a safe and effective salvage therapy. This case report provides new insights for endoscopists managing complex WON and highlights the critical importance of precise stent placement and individualized post-procedural management in the LAMS era. Finally, the conclusions of this report are limited because it was based on a single case. The true incidence, risk factors, and optimal management strategy for this complication await clarification through larger prospective studies.

ACKNOWLEDGEMENTS

We sincerely thank the patient and their family, and the medical team for their trust and support in completing this case report.