5. If there is still inadequate response to treatment (as defined above) after three endoscopic transmural drainage procedures using the designated stent type (i.e. procedure #1=stent insertion, procedure #2-3= insertion of more stents into a second drainage site ± direct endoscopic necrosectomy ± percutaneous drain insertion), the patient is defined as "endoscopic treatment failure". These patients will be referred for minimally invasive surgical debridement of WON.