AXIOS™ Lumen-Apposing Metal Stent (LAMS): Comprehensive Overview
Critical Safety Alert
The use of AXIOS and other metallic lumen-apposing stents for pancreatic pseudocyst drainage outside clinical trials is NOT recommended by consensus guidelines, receiving only moderate support (appropriateness score 7.0) due to serious adverse events including delayed bleeding, buried stent syndrome, and biliary stricture occurring in up to 50% of patients. 1
Plastic double pigtail stents remain the standard of care with >90% technical and clinical success rates, lower cost, and better safety profile. 1
FDA-Approved Indications
The AXIOS stent received FDA approval in 2013 specifically for: 2
- Transgastric or transduodenal drainage of symptomatic pancreatic pseudocysts
- Drainage of symptomatic walled-off necrosis (WON)
The stent functions as a conduit allowing solid and liquid pancreatic fluid collection contents to pass into the GI tract and permits passage of therapeutic endoscopes for debridement. 3
Contraindications & Patient Selection Caveats
Timing Requirements
- Wait 4-6 weeks from pancreatitis onset for pseudocyst wall maturation before any definitive drainage. 4
- Early intervention (<4 weeks) results in 44% complication rates versus 5.5% with delayed approach. 4
- Delay beyond 8 weeks may increase complication risk; optimal window is 4-8 weeks. 4
Anatomic Considerations
- Pre-drainage evaluation requires CECT or MRCP to delineate anatomy, with MRI preferred for depicting solid debris. 1, 4
- EUS may be needed to assess feasibility and identify intervening vessels. 1
- Complete central pancreatic duct occlusion predicts drainage failure. 4
External Drain Management
- Remove external percutaneous drains before LAMS placement when possible, as external drainage is suboptimal and complicates endoscopic intervention. 4
- External drains cause prolonged hospital stays due to pancreaticocutaneous fistula development. 4
- Multidisciplinary discussion required before attempting LAMS with external drain in situ. 4
Deployment Technique
Pre-Procedure Requirements
- Multidisciplinary support including interventional radiologist, surgeons, and anesthesiologist must be available to prevent and manage complications. 1
- Prophylactic antibiotics are mandatory and should be continued post-procedurally, as you're converting a clean system to clean-contaminated. 1, 4
- Fluoroscopy is essential for monitoring guidewire position and stent placement. 1, 4
Deployment Steps
- EUS-guided puncture of the pancreatic fluid collection using 19-gauge needle. 5
- Guidewire advancement with fluoroscopic confirmation of looping within collection. 1
- Track dilation as needed. 1
- LAMS deployment under combined EUS and fluoroscopic guidance. 1
Technical Success Rates
- Overall technical success: 97-98% across studies. 6, 7
- Clinical success: 96% overall, but significantly lower for WON (62-81%) versus pseudocysts (93-97%). 6, 8, 7
Major Device-Related Complications
Device Issues (MAUDE Database Analysis)
From 588 reports with 579 device issues: 3
- Stent malpositioning: 35.6% (most common device problem)
- Stent migration: 12.4%
- Premature deployment: 10.5%
- Material integrity problems: 9.6%
- Deployment failure: 8.1%
- Difficulty removing stent: 7.7%
Patient Adverse Events
From 250 patient complications reported: 3
- Hemorrhage/bleeding: 32.4% (most common patient complication)
- Perforation: 10.4%
- Pain: 8.8%
- Infection: 8.0%
- Death: 6.8%
Delayed Adverse Events
- Stent occlusion occurs in 29.5% of WON cases and 17.5% of pseudocyst cases. 8
- Electrocautery-enhanced LAMS is the sole predictor of treatment failure in WON (OR = 13.2). 8
- Serious delayed events including buried stent syndrome and biliary stricture reported in ongoing trials. 1
Post-Procedure Management
Immediate Post-Procedure Care
- Continue prophylactic antibiotics covering enteric gram-negative organisms and enterococci. 9
- Monitor for bleeding, infection, perforation, and pain. 5, 3
- Regular imaging to monitor response. 5
LAMS Removal Timing
Critical: Remove LAMS within 4-6 weeks after initial placement to avoid food impaction, buried stent syndrome, and other complications. 9
- Optimal timing is 4-6 weeks, allowing fistula tract maturation while minimizing stent-related complications. 9
- A well-formed fistula develops between collection and GI tract within this timeframe. 9
Stent Exchange Protocol
At time of LAMS removal, perform simultaneous exchange to double pigtail plastic stents to maintain cystogastrostomy tract and prevent fistula closure. 9
- Place one or two 7 Fr double pigtail plastic stents through the established fistula tract. 9
- Maintain plastic stents with routine exchanges every 2-4 weeks until cavity contracts to <2 cm. 9
- Recurrent collection occurs in 2.6% with proper stent maintenance versus 20% without. 9
Follow-Up Endoscopy
- Routine follow-up endoscopy at 4-6 weeks after initial drainage to assess for complete clearance of necrotic debris, fistula patency, and need for additional interventions. 9
- Direct endoscopic debridement using stone-retrieval baskets if residual solid material persists. 9
Alternative for High-Risk Patients
In frail patients or those refusing second procedure, LAMS may be left permanently with 86% 3-year patency and only 7.1% delayed adverse events. 9
Key Pitfalls to Avoid
Do not use LAMS as first-line for simple pseudocysts – plastic stents are safer, cheaper, and equally effective. 1
Do not leave LAMS in place beyond 4-6 weeks unless patient is high-risk and refusing removal – risk of buried stent syndrome and food impaction. 9
Do not remove LAMS without exchanging to plastic stents – fistula will close and collection may recur. 9
Do not use electrocautery-enhanced LAMS for WON – associated with 13-fold increased treatment failure. 8
Do not proceed without multidisciplinary team available – complications require immediate surgical/radiologic backup. 1
Do not attempt drainage before 4 weeks from pancreatitis onset – immature wall leads to 44% complication rate. 4
Cost-Benefit Consideration
LAMS is significantly more expensive than plastic stents without demonstrable differences in outcomes for pseudocysts, making routine use economically unjustifiable. 1