Pseudocysts can be managed by cyst-gastrostomy or cyst-duodenostomy alone, whereas most WONs require the additional step of endoscopic necrosectomy – the process of entering the cyst cavity to mechanically debride necrotic tissue. Because of a higher rate of technical success, endoscopic ultrasound–directed creation of the transmural drainage pathway has become standard practice. In addition, it is likely safer, allowing for the identification and avoidance of interceding vessels and other vital structures. The role of endoscopic retrograde cholangiopancreatography with pancreatic stent placement as primary therapy for PFCs is limited to the drainage of small collections (<5 cm), for which it is the preferred treatment strategy. It is as effective as ETMD, which may not be feasible or safe for small PFCs.
Plastic double-pigtail stents have traditionally been used to maintain the transmural tract for both pseudocyst and WON. Recently, however, metallic stents have become more popular. Fully covered biliary self-expanding metallic stents (SEMS) are easier to place, have a larger lumen, and are associated with improved outcomes, compared with plastic stents in observational studies of pseudocyst drainage. Lumen-apposing metallic stents (LAMS) have become the preferred prosthesis for WON drainage given the ability to near-simultaneously establish access and deploy the stent, as well as their much larger caliber lumen which permits seamless entry into the cavity with an endoscope. Based on ease and efficiency of use, LAMS are also commonly employed for pseudocyst drainage, although entry into the cavity is unnecessary.
Plastic stents have been shown to be more cost effective than LAMS for pseudocyst drainage, although the economics around biliary SEMS in this context have not been explored. Robust comparative effectiveness data defining the optimal prostheses for pseudocysts are needed. The literature comparing LAMS to plastic stents for the management of WON is mixed. Studies have shown LAMS to be more cost effective, but a small randomized trial demonstrated no difference in clinical success or in the number of procedures to achieve WON resolution.4 We generally favor LAMS for WON since large-caliber balloon dilation of the tract seems safer within the lumen of the LAMS (which could seal small perforations and tamponade bleeding vessels) than within a freshly created tract.
Secondary infection of the cavity, usually because of stent occlusion, and bleeding are the most common complications of ETMD. Even in the absence of stent occlusion, contamination of the collection after ETMD is ubiquitous and, as such, we prescribe prophylactic antibiotics for 1-2 weeks after the procedure, although this practice is not evidence based. Hemorrhage appears to be increasing in frequency with the diffusion of LAMS; this has been postulated to be due to particularly rapid cyst cavity collapse resulting in erosion of the stent into contralateral cyst wall vessels. CT angiography followed by an embolization procedure for a possible pseudoaneurysm is the mainstay of treatment. Serious venous bleeding is more challenging to address because angiographic options are limited.
Despite tremendous recent advances, several important controversies in the endoscopic management of PFCs persist. The optimal prosthesis, the importance of first-session endoscopic necroscopy (compared with stepping up to endoscopic necroscopy only if necessary), the roles of adjunctive drain placement and chemical debridement (such as hydrogen peroxide), the need for concomitant pancreatic stent placement, and the preferred long-term management of a disconnected pancreatic duct are areas for which additional research is sorely needed. We further discuss these questions and many additional technical considerations pertaining to endoscopic drainage in a recent review.5
In summary, endoscopic transmural drainage of mature PFCs is effective and safe. Existing evidence supports its use as the favored treatment modality in appropriate candidates and has rendered it a mainstay of the therapeutic armamentarium for this disease. Further studies are needed to address critical unanswered questions and to develop a uniform endoscopic management paradigm.
References
1. van Santvoort HC et al. N Engl J Med. 2010;362(16):1491-502.
2. van Brunschot S et al. Lancet. 2018;391(10115):51-8.
3. Bang JY et al. Gastroenterology. 2019;156(4):1027-40.
4. Bang JY et al. Gut. 2019;68(7):1200-9.
5. Elmunzer BJ. Clin Gastroenterol Hepatol. 2018;16(12):1851-63.
Dr. Moran is assistant professor of medicine, division of gastroenterology and hepatology, Medical University of South Carolina, Charleston; Dr. Elmunzer is the Peter Cotton Professor of Medicine and Endoscopic Innovation, division of gastroenterology and hepatology, Medical University of South Carolina. The authors have no conflicts of interest pertaining to this review.
