PROTon Pump Inhibitors and Stent OCclusion Rate Of Lumen Apposing Metal Stents

The goal of this observational retrospective cohort study in combination with an expert study is to assess the clinical relevance and management of Lumen apposing metal stent (LAMS)-occlusion and LAMS-occlusion-related complications as well as the influence of proton pump inhibitors (PPI) on LAMS-occlusion.

The main questions this study aims to answer are:

* the individual management of LAMS-occlusion and LAMS-occlusion-related complications in the respective centers participating in the study.
* if there is an association between PPI-intake and LAMS-occlusion. Participants for the retrospective cohort study will be enrolled retrospectively among European centers with expertise in pancreatology. The expert survey will be distributed European-wide to centers with special expertise in pancreatology.

A common complication of acute pancreatitis is the formation of necrosis in 5-10% of all patients, which leads to an increased overall mortality of 28% for infected necroses. Currently, lumen apposing metal stents (LAMS) are widely used to address necrotic masses. LAMS-occlusion is postulated to be a considerable complication. However, the prevalence, clinical impact and management of LAMS-occlusion-related complications remains uncertain. Moreover, the German guidelines for management of acute pancreatitis do not specify whether a concomitant proton pump inhibitor (PPI)-therapy should be discontinued or not. A recent study suggested a lower rate of LAMS-occlusions, but a higher number of required endoscopic necrosectomies upon concomitant PPI-therapy. Thus, current data are conflicting.

The investigators therefore aim to perform an expert survey and a retrospective cohort study to elucidate the clinical importance of LAMS-occlusion-related complications and the effect of PPI-intake on occlusion. First, a survey will be sent to European centers with special expertise in pancreatology. Here, the investigators aim to assess the number of LAMS applied annually, whether the experts consider occlusion a clinically relevant complication, and whether there are standard operating procedures for LAMS-occlusion and PPI-discontinuation. Second, the investigators will perform a retrospective multicenter cohort study to assess patient data for PPI intake, frequency of LAMS-occlusion and other complications using a RedCap database.

Quality assurance and data checks of the data entered will be performed by the study coordinator after the initial data entry of the participating centers. For missing data, for which the RedCap form cannot be filled out, the online forms comprise extra fields for "missing data". The data entered in the RedCap online survey will stem from paper or electronic case report forms depending which of these are used at the respective centers. Source data verification will be performed by the participating centers themselves upon data entry into the online questionnaires.

A standard operating procedure will be handed out to the participating centers which will feature any information about how data should be entered. Here, the minimum number of patients which needs to be entered into the study in order to participate will be addressed. The maximum of patients who can be entered is dependent on the respective centers; in principle all patients who received a LAMS for drainage of a WON in the respective centers can be included. As the investigators perform a retrospective study, there will be no need to account for reporting of adverse events.

Based on a power calculation of a preliminary in-house dataset from the University Hospital Goettingen the investigators aim to include a total number of 639 patients.

For missing, unavailable, non-reported or uninterpretable data, the RedCap survey will comprise extra fields as described above. In these, the participating researcher can state that data is missing. If this information is essential for the primary or secondary endpoints of our study, the data entry can be excluded from further analyses by the data monitoring committee.

For the statistical analyses of the data gathered from the expert survey the investigators will apply a Fisher/Chi2-test to assess the clinical relevance as well as the clinical management of LAMS-occlusion and LAMS-occlusion-related complications. For the retrospective cohort study, a Chi2-test will be used to address correlations between PPI-intake and LAMS-occlusion. To assess the frequency of occlusion-related-complications, risk factors for LAMS-occlusion beyond PPI-intake and differences in clinical management of LAMS-occlusion in the respective centers, logistic regression/LASSO will be applied.

Eligibility Criteria:
Retrospective cohort study:

Inclusion Criteria:

- Patients in which a Lumen apposing metal stent (LAMS) was applied into a walled off necrosis (WON) as a complication of an acute pancreatitis (AP).

Exclusion Criteria:

* Patients in which a LAMS was applied into a pseudocyst instead of a WON.
* Patients in which a LAMS was used to address a postoperative pancreatic fistula (POPF).
* Patients in which concomitant PPI-treatment was not assessed/not documented.

Expert survey:

Inclusion Criteria:

- European experts (gastroenterological interventionalists) with expertise in pancreatology

Exclusion Criteria:

* Centers which apply less than 10 LAMS per year
* Centers with less than two years experience with LAMS