In the last decades, the treatment of pancreatic pseudocysts and necrosis occurring in the clinical context of acute and chronic pancreatitis has shifted towards minimally invasive endoscopic interventions. Surgical procedures can be avoided in many cases by using endoscopically placed, Endoscopic ultrasonography-guided techniques and drainages. Endoscopic ultrasound enables the placement of transmural plastic and metal stents or nasocystic tubes for the drainage of peripancreatic fluid collections. The development of self-expanding metal stents and exchange free delivering systems have simplified the drainage of pancreatic fluid collections. This review will discuss available therapeutic techniques and new developments.

Peripancreatic fluid collections frequently occur in the context of acute and chronic pancreatitis. Fortunately, more than 50% will resolve spontaneously and, therefore, a conservative expectant approach is often the right clinical decision.

The updated Atlanta classification[1] tries to overcome the existing confusion in reporting morphologic features and complications of pancreatitis. The revised definitions differ between acute peripancreatic fluid collections associated with acute interstitial oedematous pancreatitis and acute necrotic collection occurring in necrotising pancreatitis in the acute phase. On the other hand in the late phase after more than 4 wk, the classifications describes pancreatic pseudocysts developing from interstitial oedematous pancreatitis or walled-off necrosis resulting from necrotizing pancreatitis (Table 1).

Only superinfected or clinically symptomatic pseudocysts should be considered for interventional treatment. Infection, pain, malnutrition or compression of biliary, intestinal or vascular structures might present an indication for endoscopic or percutaneous drainage. The size of the cyst alone should not influence the decision for interventional treatment.

Apart from external and transmural endoscopic drainages, some pseudocysts with communication to the pancreatic duct might be suitable for transpapillary drainage via endoscopic retrograde pancreatography (ERP). It is also possible to combine percutaneous and transmural drainages to allow frequent flushing through the external drain; similar techniques also exist for necrosectomy (hybride necrosectomy)[2,3].

Infected pseudocysts, pancreatic abscesses and infected necrosis often require drainage. Preferably, the intervention should be delayed to at least 4 wk or longer - if possible - after disease onset to allow demarcation and liquidification of the necrosis. Despite all enthusiasm for new technical developments and minimal invasive techniques, we should not forget that conservative management with antibiotic therapy alone can also result in a good outcome in selected, clinically stable patients[4-6]. Therefore, ideally, all decisions for intervention and when to intervene should be discussed in a multidisciplinary team.

Even in large bulging pseudocysts, the endoscopic ultrasonography (EUS) guided drainage is superior to the purely endoscopic approach as the puncture of vascular structures can be avoided by Doppler sonographic visualization[7,8].

The puncture of the cyst is usually performed using a 19G needle under endosonographic view. Cyst content can be aspirated for biochemical analysis [amylase or lipase, carcinoembryonic antigen (CEA)], gram stain, culture and cytology. Through the lumen of the needle a 0.035” guide wire can be advanced until it curls up in the cyst which adds stabilisation of the position and access by forming anchoring extra loops in the cavity[9-11].

Enlargement of the newly created ostium can be achieved by balloon dilatation over the guide wire. Alternatively, the canal can be widened using a cytostome and diathermy. The cystotome also allows the direct puncture of the cyst as it contains an integrated needle knife catheter which can be used instead of the 19G needle but lacks stiffness. The outer metal ring of the cystotome allows application of diathermy and the creation of a 10 Fr channel.

Stents or nasocystic tubes can be placed over the guide wire. Usually, pigtail stents are preferred due to a reduced dislocation rate. The insertion of two or more stents is desirable to improve cyst drainage and to prevent occlusion of stent and ostium as the cyst content then also empties through the gaps between the stents. Direct insertion of two guide wires into the cyst through balloon catheter or cystotome before insertion of the first stent facilitates the placement of the second stent.

Recently, the so-called multiple transluminal gateway technique has been reported for treatment of walled-off necrosis. This method requires the EUS-guided creation of two or three transmural tracts between the necrotic cavity and the gastrointestinal lumen. While one tract is used to flush saline solution via a nasocystic catheter, multiple stents in the other tracts are deployed to facilitate drainage of necrotic contents. This method was superior compared to the conventional single tract technique and might avoid the need for endoscopic debridement or open surgery in some cases[12].

The EUS-guided stent placement can be performed by endosonographic and endoscopic visualization only, however, fluoroscopy is often helpful, especially as the endosonographic view can become difficult after the cyst puncture and during stent placement (Table 2).

It can be challenging to discriminate pseudocysts from benign and malignant cystic neoplasia. Morphological criteria including vascularized septa and solid nodules in the wall of the cyst are indicators for a cystic neoplasia. Contrast enhanced ultrasound has a major impact for the diagnostic workflow of pancreatic cystic lesions[13,14]. The biochemical analysis of the cystic fluid including amylase and the CEA has proved to be helpful in the differential diagnosis between mucinous tumours (IPMN and mucinous cystadenoma with high CEA) and pancreatic pseudocysts (high amylase and low CEA).

In case of extensive necrosis, it can be necessary to extract the necrotic tissue from the walled-off cyst in order to induce the healing process. This requires the creation of a large caliber transmural orifice between the gastric or duodenal and the cystic lumen which allows the passage of a standard endoscope into the cystic cavity. In 2000, Seifert reported the first three cases of endoscopic debridement of infected retroperitoneal necrosis[15]. Since then multicenter studies have proven reduced mortality and morbidity for endoscopic necrosectomy compared to the open surgical approach[16].

Conventional endoscopic snares and dormia baskets can be used to carefully extract the necrotic material into the stomach or duodenum. Usually, many repeated endoscopic sessions (on average 4 in a recent meta analysis[17]) are necessary to mobilise the necrotic tissue completely. Complications such as perforation (4%) and bleeding (18%) can occur during endoscopic necrosectomy. Particularily the bleeding can be horrendous because often large vessels transverse the cysts or necrotic cavity. Such procedures should only be undertaken by experienced endoscopic interventionalists in high volume centers that have back up by skilled hepatobiliopancreatic surgeons and interventional radiologists. In a recent meta analysis from 14 studies, more than 80% of patients with walled-off necrosis could be successfully treated by endoscopic necrosectomy alone; this was associated with 6% mortality and a complication rate at 36%[17].

Use of carbon dioxide insufflation is mandatory to avoid air embolism.