Which are optimal for endoscopic ultrasound-guided drainage of pancreatic fluid collection: Lumen-apposing metal stents or plastic stents?

Pancreatic fluid collection (PFC) is a serious complication of acute pancreatitis that can lead to significant morbidity and mortality. The mortality rate of infectious walled-off necrosis (WON) is particularly high, with an incidence of 20% to 30%.1 Therefore, PFC management has an important role in the prognosis. Surgical interventions, including open necrosectomy and drainage, have been widely used as standard treatments; however, their high morbidity (13–53%) and mortality (6–34%) rates are concerning.2 Therefore, various alternative procedures have been developed to address these issues. For example, step-up approaches, which involve the use of treatments with increasing intensity (ranging from minimally invasive to highly invasive according to their therapeutic efficacy), have been suggested.3 Currently, the most widely accepted step-up approaches are endoscopic step-up approaches, which comprise endoscopic ultrasound-guided transmural drainage (EUS-TD) and endoscopic necrosectomy, and minimally invasive surgical step-up approaches, which comprise percutaneous catheter drainage and video-assisted retroperitoneal debridement. Bang et al.4 performed a meta-analysis to compare the outcomes of these approaches and found that, although there was no significant difference in their mortality rates during the 6-month follow-up period, new-onset multiple organ failure, enterocutaneous fistula/perforation, and pancreatic fistulas occurred significantly less often with endoscopic step-up approaches than with minimally invasive surgical step-up approaches. Additionally, endoscopic step-up approaches were associated with shorter hospital stays. These results will likely encourage the adoption of endoscopic step-up approaches for the treatment of PFC. Among the endoscopic drainage techniques, EUS-TD has become the preferred treatment modality for PFC because of its direct approach via the gastrointestinal tract and high drainage efficacy. The efficacy of EUS-TD differs in cases of pancreatic pseudocysts and WON, and it is limited in cases of WON with necrotic tissue. However, recent technical developments, such as dual-modality treatment that combines endoscopic and percutaneous drainage and the creation of multiple gateways (internal fistulae), have improved the efficacy of drainage for WON. The lumen-apposing metal stent (LAMS), which has the shape of a dumbbell with flange ends, is a recent technological innovation with potential advantages such as improved drainage, easier endoscopic transmural necrosectomy, and reduced risk of stent occlusion. Moreover, the lumen-apposing feature allows for a lower risk of perforation and peritoneal leakage of the PFC. Additionally, LAMS placement can be accomplished using a single step with an electrocautery-assisted device, thus making the drainage procedure faster and simpler than that associated with plastic stents (PS). Some retrospective studies have reported that the use of LAMS results in higher clinical success rates and lower adverse event rates than the use of PS;5, 6 therefore, LAMS are preferred to PS. However, recent randomized controlled trials (RCTs) have demonstrated that LAMS and PS are comparable in terms of PFC resolution, necrosectomy requirements, adverse events, PFC recurrence, and cost-effectiveness.7, 8 Therefore, the benefits of LAMS remain unclear. The international guidelines have not seen a consensus regarding the type of stent that should be used for EUS-TD. However, the European Society of Gastrointestinal Endoscopy guidelines state that both LAMS and PS may be considered, and the American Gastroenterological Association guidelines recommend the use of LAMS. Therefore, the optimal stent for EUS-TD for the treatment of PFC has not yet been identified. In this issue of Digestive Endoscopy, Bang et al.9 address this question by focusing on the inflammatory response and clinical outcomes after therapeutic intervention involving EUS-TD with PS or LAMS. Their study cohort included 303 patients who underwent EUS-TD with LAMS (n = 247) or PS (n = 56). The primary outcome was the presence of a systemic inflammatory response syndrome (SIRS) after EUS-TD. The secondary outcomes included persistent organ failure, new-onset organ failure, duration of hospitalization, and treatment success. The results showed that the use of LAMS was associated with fewer incidences of SIRS, new-onset SIRS, and new-onset organ failure 48 h after EUS-TD than the use of PS. Additionally, the use of PS, patients requiring high-acuity care, and the presence of ≥33% necrosis were significantly associated with SIRS or new-onset organ failure. Although there was no significant difference in the treatment success rates, the duration of hospitalization was significantly longer for the PS cohort. These findings have several important clinical implications. SIRS is a severe inflammatory response that can lead to sepsis and multiorgan failure, resulting in increased morbidity and mortality. This suggests that the use of LAMS during EUS-TD can reduce the incidences of SIRS, new-onset SIRS, and new organ failure, which, in turn, can reduce hospital stays and health-care costs. Therefore, LAMS placement should be considered for patients undergoing EUS-TD, particularly those with high-acuity care and ≥33% necrosis. This study also raises important questions regarding the mechanisms underlying differences in the inflammatory response associated with LAMS and PS. LAMS deployment is a single-step process, resulting in a short procedure time; however, PS placement is a multistep process, resulting in a relatively long procedure time. The authors also described that prolonged anesthesia could induce or increase systemic inflammation in critically ill patients. The larger diameter of the LAMS may allow better drainage and, therefore, less inflammation, whereas the PS may act as a nidus for infection and inflammation. Additionally, during PS placement, it is necessary to dilate the puncture route. This increased internal pressure in the infected cavity caused by balloon dilation may induce bacterial translocation, leading to bacteremia and subsequent clinical deterioration. Several aspects of the underlying mechanisms remain unclear; therefore, further studies are warranted to corroborate and expand the findings of this study. This study also highlighted the importance of risk stratification for patients undergoing EUS-TD. Patients with high-acuity care and those with ≥33% necrosis were at higher risk for SIRS or new-onset organ failure. Tsujimae et al.10 evaluated the spread of PFC by dividing the computed tomography image of the abdominal cavity into eight sections and found that the presence of three or more PFC-occupied regions was a significant factor associated with ineffective EUS-TD using PS. The spread of the PFC may be associated with factors that aggravate the inflammatory response. Therefore, the stent type and other factors should be considered carefully based on the patient's condition, degree of necrosis, and spread of the PFC during the decision-making process. It is important to note that this study had some limitations. First, it was retrospective and observational, and there may have been confounding factors that were not considered during the analysis. Second, the sample size of the PS cohort was smaller than that of the LAMS cohort, which may have affected the power of the study. Finally, the study did not evaluate long-term outcomes, such as PFC recurrence and patient survival. Further RCTs with larger sample sizes should be performed to confirm these findings and assess the long-term outcomes of EUS-TD using LAMS and PS. In conclusion, the study by Bang et al.9 provides important insights regarding the impact of the stent type on the inflammatory response of patients undergoing EUS-guided PFC drainage. The use of LAMS was associated with fewer incidences of SIRS, new-onset SIRS, and new-onset organ failure compared with the use of PS, particularly for patients with high-acuity care and ≥33% necrosis. These findings have significant clinical implications and highlight the importance of careful consideration of the stent type and risk stratification for the management of PFC. Further studies are necessary to address these unanswered questions and optimize the outcomes of EUS-guided PFC drainage. Authors declare no conflict of interest for this article. None.