Complications of diagnostic and therapeutic Endoscopic Ultrasound

Best Practice & Research Clinical Gastroenterology 30 (2016) 807e823

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Best Practice & Research Clinical Gastroenterology

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Complications of diagnostic and therapeutic Endoscopic Ultrasound Sundeep Lakhtakia, MD, MNAMS, DM, FASGE, Senior Consultant Gastroenterologist * Asian Institute of Gastroenterology, 6-3-661, Somajiguda, Hyderabad, Telangana, 500082, India

a b s t r a c t Keywords: Complications of EUS EUS guided FNA EUS guided drainage of pancreatic fluid collection EUS guided biliary drainage EUS guided PD drainage

Endoscopic Ultrasound (EUS) provides the unique opportunity to visualize, interrogate and intervene gastrointestinal (GI) luminal, mural or peri-luminal structures and pathology with negligible adverse effects. Diagnostic, upper GI and rectal EUS is feasible, extremely safe, and efficacious. Most EUS guided interventions are safe, effective and minimally invasive, compared to peers in the percutaneous radiological or surgical procedures. As with any endoscopic procedure, EUS and its guided interventions may be accompanied by adverse events. EUS related complications are generally infrequent in expert hands, and mainly include bleeding and perforation. However, the nature and severity of adverse events associated with each EUS guided procedure are unique. Hence, it is paramount for endosonographer to have sufficient knowledge of the indications, techniques, and potential risks involved before contemplating any given procedure. Most common intervention with EUS is transmural fine needle aspiration (FNA), which is an extremely safe procedure. EUS guided drainage procedures are rapidly evolving with newer devices and methods being employed. Among them, EUS guided drainage of pancreatic fluid collection-pseudocyst or walled off necrosis (WON), has largely replaced other methods (surgical, percutaneous or non-EUS endoscopic) with acceptable complications. Currently, dedicated metal stents are more widely used compared to plastic stents for drainage of PFC, especially WON. EUS has made a definite impact in biliary access and drainage of obstructed biliary system, in patients where ERCP has failed or is technically not possible, closely competing with percutaneous

* Fax: þ91 40 23324255. E-mail address: [email protected]. http://dx.doi.org/10.1016/j.bpg.2016.10.008 1521-6918/© 2016 Elsevier Ltd. All rights reserved.

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biliary drainage. In spite of some complications, recent improvement in devices for bilio-enteric fistula creation and stent designs, has added to its safety and efficacy. EUS guided pancreatic duct drainage remains the most challenging of EUS guided interventions where in-roads are being made. © 2016 Elsevier Ltd. All rights reserved.

Abbreviations EUS Endoscopic Ultrasound FNA Fine Needle Aspiration PFC Pancreatic Fluid Collection WON Walled Off Necrosis PC Pseudocyst EUS-BD EUS guided Biliary Drainage EUS-CDS EUS guided Choledocho-Duodenostomy EUS-HGS EUS guided Hepatico-Gastrostomy EUS-RV EUS guided Rendezvous TCB Trucut biopsy PD Pancreatic Duct CBD Common bile Duct CPB Celiac Plexus Block CPN Celiac Plexus Neurolysis SEMS Self Expanding Metal Stent FCSEMS Fully Covered Self Expanding Metal Stent AE Adverse Event MPD Main Pancreatic Duct FNI Fine needle Injection RFA Radio Frequency Ablation GIT Gastrointestinal Tract US Ultrasound ERCP Endoscopic Retrograde Cholangio Pancreatography CECT Contrast Enhanced Computed Tomography DEN Direct Endoscopic Necrosectomy

Introduction Endoscopic Ultrasound (EUS) over last three decades has established itself as a vital technology in the field of endoscopy. Historically, EUS started as a diagnostic procedure, performed mainly with radial echoendoscopes, and meant for upper GI cancer staging. Diagnostic EUS, is currently being performed with either Radial or Linear echo-endoscope. Like other endoscopic procedure, diagnostic EUS is a safe and efficient procedure in expert hands. Performing EUS guided FNA from peri-luminal lymph nodes or solid lesions, takes the endosonographer to next level of expertise in field of EUS, where the device (FNA needle) and the procedure pose additional technical challenges. There is invasion of the sterile areas by transmural puncture from the luminal side of FNA needle, posing a risk howsoever small, of introducing infection. EUS guided fine needle injections (FNI), include injections of liquid agents (tattooing) or solid agents (fiducial implantation) are technically extension of EUS guided FNA. Procedures like EUS guided celiac plexus neurolysis, or coil placements and EUS guided RFA are advanced FNI pose additional challenges of avoiding adjacent vital structures.

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Still further, with increasing degree of technical difficulty, are EUS guided therapeutic interventions, including drainage of pancreatic fluid collections, biliary and pancreatic duct drainages. There are many refinements currently taking place in these specialized EUS procedures to make them safe and efficient to enhance their wider use. Most current literature suggests EUS guided transmural interventions are feasible, safe, and efficacious, and are generally less invasive compared to peers in the percutaneous radiological or surgical procedures. There are reports of adverse events with EUS-guided transmural interventions. However, it is paramount for endosonographer to have sufficient knowledge of the indications, techniques, and potential risks before contemplating any given procedure. EUS related complication (adverse event) can be broadly classified according to the ‘EUS intervention/procedure’ being performed. Some of the common factors leading to any EUS associated complications can also be related to e the operator's experience, general health condition of the patient, disease per se, echoendoscopes and sedation. The usual complications associated with diagnostic or interventional EUS are perforation, bleeding and infection, apart from those, which are peculiar to specific EUS intervention. In this chapter, complications associated with various EUS procedures will be discussed. In addition, emphasis is placed on how to prevent and manage such adverse events. Complications of diagnostic EUS Currently available echoendoscopes, both radial and linear varieties, have the ultrasound (US) transducer located at the tip, which is non-flexible. This makes the terminal 4e5 cm length of the echoendoscopes more rigid than standard endoscopes. Also, the optics of most of the currently available echo-endoscopes have oblique viewing. The optical lens is located about 1 cm or more from the tip of the scope. Due to the oblique direction of endoscopic view, the echo-endoscope insertion and advancement of the instruments, especially across the bends, are semi-blind maneuvers. The adverse events described, though rare, include e perforation, bleeding and infection. Perforations can occur at natural narrow segments of gastrointestinal tract GIT such as cricopharyngeal region or duodenal bend between first and second part, or at any pathological stricturous segment e.g. esophageal cancer. Perforation is less common with linear scope due to its smooth short curved transducer at tip than rigid wider shaft in the pre-terminal part. This helps ease the advancement of the instrument through the GIT. Also the current generation echo-endoscopes are thinner and more flexible. Evaluating only cervical esophageal perforation, in a USA survey involving 86 physicians, there were 16 perforations reported among 43,852 (0.03%) procedures with one death [1]. Majority (94%) of cervical perforations occurred in older patients (>65 years age), with 44% patients having history of difficult intubation during a prior upper endoscopic procedure. Radial echo-endoscope was involved in 15 perforations (94%). Less experienced EUS operators (less than 1 year of experience) were associated in 12 perforations. Esophageal cancer and esophageal strictures are both associated with increased incidence of esophageal perforation. Cancer of esophagus with stricture often restricts the passage of EUS scope for staging, thus limiting complete and accurate assessment for both T and N staging, especially of the region beyond the proximal end of stricture [2,3]. Dilation of the stricture carries risk of perforation in up to one out of four cases [2e6]. Sequential bougienage to no more than 16 mm has been reported in 120 patients without perforation [5,6]. Prospective studies of the role of dilation in patients with obstructing esophageal cancer undergoing EUS examinations by experienced operators did not report an association between perforation and dilation [5,6]. Through-the-scope mini-probes represent another alternative in patients with a luminal stricture [7e9]. Complications of EUS FNA FNA is most common EUS intervention performed to obtain tissue from peri-luminal lymph nodes or masses and to aspirate the contents of cystic lesions (e.g. pancreatic cysts) for analysis.

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Morbidity associated with EUS-FNA has been reported in the prospective series range between 0% and 2.5%, with one death reported from a pooled series of 2468 patients (0.04%) [10,11]. Complications mostly included infection, bleeding, and acute pancreatitis. Frequency of complications reported in retrospective series of EUS-FNA is much less as compared to prospective series [12]. Currently available EUS-FNA needles have a caliber of 19, 22 and 25 gauge with variations in design. A 19G trucut biopsy needle (Quick-Core; Wilson Cook Medical) was designed with intent to obtain EUS guided core biopsy specimens. This device obtains tissue via a spring-loaded cutting sheath and a tissue tray to capture the specimen. This needle is stiff with increased risk of perforation of the biopsy channel of echo-endoscope. Because of the limited flexibility of the Trucut needle, in most studies EUSTCB was not performed trans-duodenally. In addition, because of device issue, only lesions 2 cm can be punctured. There has been report of an infectious complication after trucut biopsy of a mediastinal mass [13]. However, EUS-TCB presents a safety profile similar to that of EUS-FNA, in experienced hands. Infectious complications The incidence of bacteremia after EUS-FNA (including EUS-FNA of rectal and perirectal lesions) is low, usually in-consequential and similar to that observed after upper GI endoscopy or EUS without FNA [14e18]. Also, patients who developed bacteremia after EUS-FNA, rarely manifest with clinical features of illness. Therefore, prophylactic antibiotics are not recommended for EUS-FNA of solid lesions or lymph nodes [19]. Also, recent guidelines do not recommend antibiotic prophylaxis for the prevention of infective endocarditis in patients with cardiac risk factors undergoing EUS-FNA [19]. However, sepsis has been reported after FNA from pancreatic cystic lesions as well as mediastinal cysts and therefore, prophylactic antibiotics are recommended in these cases [20e23]. Some experts also recommend prophylactic antibiotics after trans-rectal EUS-FNA [24]. Pancreatitis The risk of pancreatitis associated with EUS guided pancreatic FNA for pancreatic mass or cyst is very low and ranges from 0% to 2% [22,25e27]. Pancreatitis risk is due to the injury of normal intervening pancreatic parenchyma or the pancreatic duct. It may be logical to use shortest distance to reach the pancreatic lesion avoiding main or side branch pancreatic duct, to prevent any post FNA pancreatitis. Gress et al. reported a two cases (2% rate) of pancreatitis among 100 consecutive patients undergoing pancreatic EUS-FNA [27]. They reported serum amylase and lipase levels can be asymptomatically elevated after EUS-guided fine-needle aspiration. Both patients who developed acute interstitial pancreatitis, recovered with conservative therapy. Eloubedi in their study of 158 patients who underwent EUS-FNA of pancreatic lesion reported ten immediate self-limited complications occurred (6.3%) [26]. In early follow up between 24 and 72 h, 22% reported at least one symptom, all of which were minor except in three cases (one self-limited acute pancreatitis and two emergency room visits, one of which led to admission). Katanuma et al., in their retrospective review of 316 consecutive patients examined post-procedural events and determined the risk factors associated with EUS-FNA of pancreatic solid lesion [28]. They reported incidence of post-procedural adverse events was 3.4% (including moderate to mild pancreatitis, mild abdominal pain, and mild bleeding). Uni-variate analysis showed that the incidence of postprocedural events was significantly increased in patients with tumors 20 mm in diameter, and those with pancreatic neuro-endocrine tumors (PNET), and patients who had intervening normal pancreas for accessing the lesion. Multivariate analysis identified tumors measuring less than or equal to 20 mm in diameter and case of PNETs were an independent risk factors. Hemorrhage The bleed following EUS FNA is generally mild and self-limiting. Clinically significant bleeding is a possible, but very rare complication of EUS-FNA. The incidence reported in large prospective series ranged between 0% and 0.5% [11]. Self-limited intra-procedural bleeding with no clinical consequences is more common. Significant bleed can occur if major or large vessel is punctured or there is additional

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coagulopathy. Extra-luminal bleeding (visible as an expanding echo-poor region adjacent to the sampled lesion) has been reported to occur during 1.3%e2.6% of procedures [29], and intra-cystic bleeding (gradually expanding hyper-echoic area within the cyst) during 6% of EUS-FNA of pancreatic cysts [30]. In both situations, the management consisted in stopping of further needle passes, observation by EUS, and a short course of antibiotics to prevent infection [29,30]. One study specifically evaluated, over a 13-month period, extra-luminal hemorrhage in patients undergoing EUS-FNA [29]. Three cases of extra-luminal hemorrhage occurred among 227 patients, with an overall rate of 1.3%. These occurred during aspiration of a pancreatic islet cell mass, a peritumoral lymph node in a patient with esophageal cancer, and a pancreatic cyst. In all cases, the hemorrhage was seen with US, and mechanical pressure (in an attempt to tamponade the hemorrhage) was applied with the endoscope. Rare cases of intra-procedural luminal bleeding requiring intervention (adrenaline injection and hemostatic clips) have been described [11]. There is a recent case of gastric abscess formation after pancreatic cancer FNA [31]. One fatal case due to bleed after EUS FNA has been reported [10]. Gress et al., in study performed two decades ago, using very early model of FNA needles reported two episodes of clinically significant bleeding after EUS-FNA of pancreatic lesions, one of which resulted in death [32]. They concluded that risk of severe bleeding for EUS FNA of pancreatic masses was 1% (1/121), and risk of death in less than 1%. EUS-guided sampling should be avoided in patients taking oral anticoagulants [33]. According to a recently issued ESGE guideline on endoscopy and antiplatelet agents (APA), EUS-FNA of solid masses can be performed in patients taking aspirin or NSAIDS, but not in patients taking thienopyridines (e. g. clopidogrel). EUS-FNA of cystic lesions should not be performed in patients taking APA of any kind [34]. If a change in antithrombotic therapy is required for performance of EUS-FNA, the thromboembolic risk in a given patient and the risk-to-benefit ratio should be considered [33,34]. Tumor seeding Three cases of tumor seeding following EUS FNA have been reported to date [11]. A retrospective study suggests that peritoneal carcinomatosis related to pancreas cancer may occur more frequently after percutaneous as compared to EUS-guided FNA [11]. Bile peritonitis Bile peritonitis is a rare complication of EUS-FNA. It can occur as result of puncture of gall bladder or bile duct. The risk is higher if gall bladder bile is targeted rather than a gall bladder mass. EUS guided bile aspiration directly from the gallbladder in one prospective study resulted in biliary peritonitis in two of the three patients, resulting in the termination of the study [35]. EUS-FNA of solid gallbladder masses has been reported as safe in one small series of six patients [36]. There is a case report of bile peritonitis requiring laparotomy following EUS-FNA of a pancreatichead mass with biliary obstruction, who had inadvertent perforation of distal CBD [37]. Celiac plexus blockade/neurolysis EUS can be used to perform celiac plexus blockade (in patients with chronic pancreatitis) or neurolysis (in patients with pancreatic cancer) as a means of achieving analgesia. The technique involves the delivery of corticosteroids (in blockade) or absolute alcohol (in neurolysis) plus a local anesthetic into the celiac plexus via EUS-guided injection with an FNA needle. EUS-guided Celiac Plexus Block (CPB) enables the endoscopist to easily and accurately determine the location for injection, unlike the percutaneous posterior approach injection, performed under CT or fluoroscopy guidance. For EUS-guided Celiac Plexus Neurolysis (CPN), the complications include orthostatic hypotension (in 3.4%e20.0% cases), transient increase in pain (in 6.8%e9.0%), and diarrhea (in 10%e17%) and abscess formation [38e41]. There have been isolated reports of retroperitoneal abscesses after EUS-guided celiac plexus block [42].

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Patients should receive adequate intravenous hydration peri-procedure to reduce the possibility of orthostatic hypotension. Neurological complications (lower extremity weakness with or without paresthesia, paraplegia), are distinctly unusual under ‘anterior’ EUS guidance (unlike ‘posterior’ percutaneous approach) due to avoidance of para-spinal nerves. However, there has been a recent case report of spinal cord infarction with EUS guided CPN [43]. Similarly vascular complications are avoided under EUS guidance due to visualization of interposing vessels with Doppler. There has been a case of fungal brain abscess after EUS CPN in a patient with alcoholic chronic pancreatitis [44]. A mortality has been reported following EUS-guided neurolysis using alcohol in a patient with chronic pancreatitis having a suspicious pancreatic mass with negative cytology [45]. Pancreatic fluid collection drainage The management of pancreatic fluid collections (PFC), which includes pseudocyst or walled off pancreatic necrosis (WON), has evolved over time. Traditionally, the drainage of PFCs was accomplished by surgical or percutaneous methods. However, endoscopic trans-enteric drainage is now the preferred route [46,47]. It started with the use of duodenoscope or forward viewing endoscope to drain the pseudocyst bulging in stomach or duodenum. However, with the use of EUS, the safety and efficacy of PFC drainage has improved further [48e50]. EUS provides the ability to identify and avoid vascular structures (using Doppler) between the fluid collection and the upper GI lumen while draining PFC. EUS also helps to assess maturity of PFC and its wall thickness, and so as to select thinnest point of entry, even in non-bulging collections. The ability to confirm the presence or absence of solid or necrotic components within the PFC cavity is an additional benefit of EUS guided drainage of PFC. EUS-guided drainage has become a mainstream procedure for the management of symptomatic PFC, with technical success greater than 90% and treatment success varying between 70% and 90%, depending on the characteristics of the PFC being drained [51,52]. The EUS drainage procedure of PFC is reasonably safe in experienced hands. The complications reported with EUS guided drainage of PFC includes: perforation, bleeding, infection and migration of stent. Prospective, randomized trials have conclusively proven that the technical outcomes and safety profile of EUS is superior to conventional endoscopy for transmural drainage of pancreatic pseudocysts [53]. Despite these inherent advantages, perforation and bleeding at EUS-guided drainage are the most frequent complication in several studies [54e56]. The frequency of these complications may vary according to the type of PFC and procedural techniques. Early case series of endoscopic drainage of pseudocyst using duodenoscope [57] or EUS [54] documented success rates of 78% and 89% with complication rates of 7% and 4% respectively. Since then, several studies have validated these initial findings, with studies quoting success rates ranging from 80% to 100% and complication rates averaging around 10%, mainly bleeding and perforation [51,54,55,58e62]. Complication rate can vary according the nature of pseudocyst. Sadik et al reported a 94% success with 5% complication rate in simple pseudocysts as compared to 80% success and 30% complication rate in infected pseudocysts [63]. Varadarajulu et al. reported 93.5% success and 5% complication rate in sterile pseudocyst versus a 63% success and 16% complication rate in infected pseudocysts [64]. This suggests that while EUS-guided drainage is still efficacious, infected pseudocysts are more difficult to drain associated with a higher complication rate. Additional efforts, like multiple stents or naso-cystic tube for external irrigation, may be required. Perforation Perforation has been reported as a complication in several reports (Fig. 1) [54e56,60]. Varadarajulu et al., evaluated for frequency of complications undergoing EUS-guided drainage of pancreatic fluid collections in 148 consecutive patients [65]. They reported perforation in two patients requiring surgery, with pseudocyst (PC) located primarily in the uncinate region of the pancreas, which were drained via stomach. PC in these patients was reportedly close to gastric wall on EUS, with adequate immediate drainage of cyst contents following stent placement. CT scan of the abdomen revealed that

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Fig. 1. Erect X-ray abdomen in a patient showing gas under both domes of diaphragm after EUS guided drainage of pseudocyst. Two double pigtail plastic cysto-gastric stents are visible.

the free end of the double pigtail stents was lodged in the retro-peritoneum. The surgical findings confirmed absence of adherence between pseudocyst and stomach wall. The likely pathogenesis of perforation proposed by authors was that following transmural stenting; the pseudocyst got decompressed and moved further away from the stomach wall, leading to perforation. On the contrary, no complication occurred in the uncinate PFC that was drained trans-duodenally. There are other studies reporting perforation following EUS guided pseudocyst drainage [54e56]. A majority of perforations in these series occurred during the transmural puncture of the PFC using electro-cautery. Other causes of perforation associated with EUS guided drainage include use of noncoaxial needle knife to create fistula or very large caliber balloon for initial dilation. The projecting needle knife may go in a tangential direction and dissect the wall causing perforation. Such complications can be avoided by use of co-axial over the guide-wire cystotome. Some authors have suggested graded dilation technique without the use of electro-cautery to prevent perforation [52,66]. A general caution during EUS guided drainage is use ultrasound and fluoroscopy image primarily in focus during most of the procedure. Avoid endoscopic view as far as possible in the initial steps of drainage procedure. Keep the guide-wire in EUS view, so as to prevent any looping of it in the lumen or extra-luminal space. Most perforations are generally small and can be managed successfully by conservative measures, especially if CO2 has been used as gas for insufflation, with nasogastric drainage and intravenous antibiotics. In a recent Asia Pacific consensus statement, the majority of perforations associated with WON drainage and DEN (71.4%, 20/28) could be treated conservatively [50]. Rest of non-responders, required surgery (Fig. 2). Bleeding Bleeding occasionally can occur during EUS guided drainage, in spite of avoidance of interposing blood vessel either at site of puncture (entry point) or from within the cavity. Puncture site bleeding can occur in patients with collaterals developing as result of segmental portal hypertension. Occasional

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Fig. 2. Exploratory laparotomy findings of the patient with perforation after EUS guided drainage show non-adherent pseudocyst wall to stomach with the distal end of plastic stents in peritoneal cavity.

small non-obvious vessels, either within the PFC wall or within the depth of PFC, may bleed after rapid decompression of the PC due to release of tamponade. Use of needle knife, with or without wire guidance, also pose a risk for bleed from puncture site. Bleeding has been reported in a patient with underlying acquired factor VIII inhibitors [65]. To prevent bleeding due to EUS guided drainage, coagulation parameters should be checked in highrisk patients or those with suggestive history. Avoid needle knife to create fistula after initial puncture. Use over the wire electrosurgical device or graded mechanical dilation. Endoscopic methods described to control bleed after drainage includes: dilute epinephrine injection, balloon tamponade, through-the-scope endo-clips and electro-cautery, placement of largediameter FCSEMS, or hemostatic powder. Placing large caliber fully covered stent, if bleeding is noted during drainage procedure preferably controls it. The ability of FCSEMSs to tamponade bleeding is attributable to a combination of stent covering, tensile strength, and ability to self-expand [67]. Also, FCSEMS provide the advantage to perform subsequent DEN, if required. One should consider pseudo-aneurysm as a source of bleed, which can be confirmed with dynamic CECT [50]. In case of uncontrolled bleeding, angiographic embolization or surgical exploration may be required. Hence, a multidisciplinary approach involving skilled interventional endoscopists, radiologists, and surgeons is necessary to manage cases of severe bleeding and other complications. Stent migration Plastic stent migration inside the PFC is another complication, which may occur if the site of puncture is in esophagus or at gastric cardia, where the endoscopic visualization can be challenging at the time of final deployment of stent [65]. Gradual withdrawal and torquing of the echo-endoscope during stent deployment is crucial to avoid this complication. The risk of internal migration is higher with the use of short length dedicated SEMS for PFC drainage, which may occur due to rapid expulsion of cyst content into stomach. The situation can be salvaged if the guide-wire is still in situ and complication detected at the procedure [68]. Otherwise the fistula track has to be re-dilated with balloon and internally migrated stent retrieved from within the cavity.

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Infection Infection occurs due to incomplete drainage of PFC (due to blocked stents) or with the introduction of infection into a previously sterile PFC, especially WON. These situations are managed with repeat endoscopic drainage [65]. The fistula track is dilated with balloon and fresh stent or naso-cystic tube placed. Previous stent assist as a guide to access the cavity under fluoroscopic guidance. Infection is a well-recognized complication that is more likely encountered following drainage of necrotic collections [69]. While some cases can be managed endoscopically by the placement of nasocystic catheters and additional transmural stents, surgery is inevitable in others. Infection of solid debris within WON is often managed with direct endoscopic necrosectomy (DEN). Dilating the fistula, besides the previous placed plastic stents, with large caliber balloon allows access to the cavity with endoscope. The debris is scooped out using variety of endoscopic accessories. DEN is a labor-intensive procedure with attending complications of perforation and bleeding from larger vessels at its base. The use of dedicated large caliber FCSEMS for PFC drainage have largely reduced the requirement of the DEN or made it easier with no requirement of dilation at each session of DEN. Plastic stents have been used earlier for EUS guided drainage of PFC with encouraging results. They are optimal for the drainage of PC with clear content. However, the debris within WON may occlude the small caliber plastic stents or its surrounding cysto-enteric fistulous opening, leading to inefficient drainage [69]. Recent data suggests encouraging results with wide caliber fully covered self-expandable metal stents (FCSEMS) to drain PFC due to their decreased need for re-intervention because of better drainage [50,70e79]. Conventional FCSEMS (meant for biliary drainage or esophageal stricture) in draining PFCs have risk of spontaneous stent migration due to longer length and lack of lumen apposing properties. Furthermore, the narrow lumen of biliary SEMS poses a challenge for direct endoscopic necrosectomy (DEN). The development of the specially designed dedicated FCSEMS for PFC drainage, which is short, bi-flanged and fully covered, has helped overcome some of the limitations associated with conventional FCSEMS. Air embolism Air embolism is a rare complication associated with DEN using air insufflation, and is potentially severe and even lethal. Air embolism during endoscopic necrosectomy has been anecdotally reported [80e83]. This risk has largely reduced with use of CO2, which is readily absorbed. Recently, one case of fatal CO2 embolism was also reported, showing that even CO2 insufflation can sometimes be associated with embolism [84]. Gas embolism should be considered promptly if cardiovascular and/or respiratory symptoms develop abruptly during endoscopic necrosectomy, and protocols should be available to manage these critical situations. Caution should be undertaken in the event that this rare and dangerous gas embolism occurs during endoscopic necrosectomy using CO2 insufflation [50]. Direct endoscopic necrosectomy (DEN) DEN is occasionally required to clean up the infected/symptomatic debris within the WON after initial drainage. In recent Asian consensus on endoscopic management of WON, the morbidity and mortality rates associated with endoscopic necrosectomy were 27.3% (173/633) and 4.4% (28/633), respectively [50]. The most common complication associated with endoscopic necrosectomy was bleeding (12.6%; 80/633), which may occur during both balloon dilation of the gastrointestinal tract fistula and necrosectomy. In this consensus, bleeding associated with DEN, was classified as immediate or delayed, for detailed analyses of pooled data comprising 80 cases. The severity of bleeding was: mild (n ¼ 67), moderate (n ¼ 2), severe (n ¼ 9), and unspecified (n ¼ 2) [50]. Perforation (4.4%; 28/633) was the second most frequent complication after bleeding. Air embolism was observed in five patients (0.8%; 5/633) [50].

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EUS-PD drainage EUS PD is a recently developed treatment alternative for patients with pancreatic duct obstruction who fail conventional drainage at ERCP. The two major techniques within the broad realm of EUS-PD include, EUS-guided rendezvous and pancreatico-gastrostomy. It is one of the most technically demanding EUS interventions with associated high risk and failure rate. Technical failures are mainly due to challenges in orienting and maintaining the position of the echo-endoscope along the axis of the main pancreatic duct, inability to dilate the transmural tract due to dense fibrosis, and difficulty with endo-therapy due to the acute angle at which the pancreatic duct was accessed at EUS [85e90]. The rate of procedural complications varies between 5% and 43% and include perforation, bleeding, pancreatitis, fever, pancreatic duct leak and post-procedure pain. Most studies report a medium-term pain relief in 60%e70% of patients following PD stenting. Stent migration and/or occlusion has been reported in 20%e55% of patients. In a recent retrospective multi-center study including 80 patients undergoing EUS guided PD drainage after failed ERCP, the overall adverse event (AE) rate was 20% [91]. Authors divided AEs into ‘immediate AEs’ (<24 h of the procedure) and ‘delayed AEs’ (>24 h post-procedure). They also classified AEs into ‘minor AEs’, such as post-procedure pain or bleeding not requiring intervention, and ‘major AEs’, such as pancreatitis, pancreatic fluid collection or abscess, perforation, MPD leak, and death. Immediate AEs occurred in 20% of patients, including 4 minor (post-procedure pain e 3, and bleeding e 1, controlled with hemoclip placement at the puncture site) and 12 major complications (post-ERCP pancreatitis e 6, PFCs e 4, MPD leak e 1, and perforation e 1). Technical failure trended toward being a predictor of immediate AEs, although the difference was not statistically significant [91]. Delayed AEs occurred in 11% of patients (n ¼ 9). All of these patients also had immediate AEs. 1 was mild (pain post procedure), the remaining were major (1 perforation e requiring surgical repair, 2 pancreatitis, 1 MPD leak, and 4 abscesses treated with antibiotics). 4 were in patients who did not achieve technical success (perforation e 1, pancreatitis e 2, abscess e 1); the remaining 6 achieved clinical success. Technical failure also trended toward being a predictor of delayed AEs [91]. EUS guided biliary drainage EUS is increasingly being used to access and/or drain the obstructed biliary system. Diagnostic cholangiography was first reported by Wiersema et al. by EUS-guided puncture of the bile duct in 1996 [92]. Subsequently in 2001, Giovannini et al. described EUS-guided biliary drainage for patients who failed conventional ERCP [93]. Since then the EUS-guided biliary interventions have been evolving. Currently, in patients with failed ERCP, especially with malignant biliary obstruction, EUS assists access e via duodenum (into CBD) or stomach (via liver), and direct drainage. EUS guided biliary drainage procedures include EUS guided choledocho-duodenostomy (EUS-CDS) and EUS guided hepatico-gastrostomy (EUS-HGS). These options are now reasonably well established and serve as an alternate to percutaneous trans-hepatic biliary drainage (PTBD) [48,94e97]. EUS guided biliary access followed by ERCP as rendezvous procedure is generally considered for benign biliary disorders (stone disease), and occasionally for malignant biliary obstruction. EUS guided biliary drainage procedures have high technical and clinical success rates (more than 90%) at high-volume centers. Overall reported complications for both EUS-CDS and EUS-HGS procedures remain high, at 10%e30% [98]. Also the accompanying complications are quite different for both these drainage procedures. The selection of dilated biliary access route is dependent on biliary and gastro-duodenal anatomy. For an inoperable malignant lower biliary obstruction, EUS-BD is preferred over EUS-guided rendezvous technique (EUS-RV) and PTBD. If both routes of drainage options are possible, EUS-CDS is preferred over EUS-HGS, as the stent dysfunction rate is higher with latter. Kawakubo et al reported that the ‘stent dysfunction rate’ and ‘3-month stent patency rate’ were 21% and 80% for EUS-CDS, and

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32% and 51% for EUS-HGS, respectively [99]. However, in patients with hepatic hilar biliary obstruction, EUS-HGS is the only option for EUS guided drainage. The complications associated with EUS guided biliary interventions are related to route of entry into the biliary system (trans-gastric via hepatic route or trans-duodenal via CBD), type of devices used, stage or extent of disease and experience of the operator. The usual complications include: bile leak and bile peritonitis, perforation, bleeding, and pneumoperitoneum. Bile leak Bile leak occurs due to trickling of the bile fluid from the obstructed high-pressure system into the potential space between the GI wall and bile duct wall, manifesting either as biloma or bile peritonitis. It is more common with the use of small caliber plastic stent or uncovered SEMS. Kawakubo et al reported that bile leakage was more frequently observed in patients who underwent plastic stent placement (11%) than in those receiving covered metal stents (4%) [99]. Most bile leakages are selflimiting and improve with conservative management. Use of transmural plastic stent is associated with bile leak because of trickling of bile besides the stent into peritoneum. Hence, fully covered SEMS (FCSEMS) are preferred to prevent bile leakage into the potential. Perforations Perforations are due to creation of large opening in the GI wall at the entry point. Prachayakul et al reported that the use of a needle-knife for fistula dilation in EUS-BD should be avoided if possible [100]. Perforations can be largely avoided by using over-the-wire devices (coaxial electro-surgical device or tapered bougie or small caliber balloon of 4e6 mm) to create small opening. The needle-knife is not coaxial; hence its use is accompanied by a risk of perforation or bleeds. Large caliber balloons (>10 mm diameter) create large defects in fistula on both lumen wall side (leading to perforation) and biliary wall side (causing bile leak). If the procedure in unsuccessful, the transmural defect can be closed with endoscopic placement of mechanical clips. Pneumo-peritoneum Pneumo-peritoneum is currently uncommon due to widespread use of CO2 for endoscopic insufflation. Most can be managed conservatively with antibiotic and continuous naso-gastric drainage. Cholangitis Cholangitis occurs due to incomplete or unsuccessful drainage of the obstructed biliary system, which may require re-intervention using standby endoscopic procedures or PTBD. Pancreatitis Pancreatitis occurs due to manipulation of papilla from inside out (unlike ERCP) by ante-grade procedure e either ante-grade stent placement of SEMS or EUS rendezvous procedure. It is also likely that the risk of pancreatitis may be attributed to failure of prior ERCP. However, the chances of pancreatitis are negligible with EUS-HGS, as the papilla is not manipulated. Stent migration Adverse events associated with SEMS include failure to deploy due to thick or stiff delivery system and stent migration. Internal stent migration is a severe complication of EUS-HGS, with one reported

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fatality [101,102]. Usually, the liver and stomach are non-adherent, and there is a potential space between the two organs. Fully covered metal stents (FCSEMS) can potentially migrate into the liver or peritoneal cavity, with foreshortening of expanding stent, especially if the protruding luminal part of the stent is short. This complication is more common with EUS-HGS. Methods employed to prevent internal migration of FCSEMS, include using long SEMS with bare inner part (for anchoring within liver and avoid blockage of draining biliary side branches), leaving longer segment (5 cm) in the gastric end of HGS, or placing anti-migratory features on stent. There are few reported uncommon complications peculiar to EUS-HGS, which include liver abscess, biloma [103], focal cholangitis, pseudo-aneurysm [104] and bile duct obstruction caused by epithelial hyperplasia. Most complications with EUS-BD are associated with beginners in this field, hence experts recommend mentor's supervision during at least the first 20 cases [98]. Overall EUS-HGS has many more types of complications than EUS-CDS. A unique complication associated with EUS-CDS is ‘double penetration of the duodenum’. In this, duodenum wall is punctured twice due to folds. After EUS-CDS, double penetration of the duodenum was seen in 4% (4/101) in one series [98]. Double penetration of the duodenum may cause retroperitoneal perforation. Recently, a newly designed lumen-apposing SEMS has been developed to reduce bile leakage [98 104,105e109]. In conclusion, EUS and EUS guided interventions can be associated with various complications, though uncommon. These may be more common during the early phase of career of an endoscopist; hence supervised training programs and mentorship are essential. Fortunately, most of the adverse events are minor. Some of the complications are unique to the procedure involved for which the operator must be aware and manage accordingly. Because of their infrequency, all EUS related complications, both minor and major, should be systematically recorded and collaborated with peers. Serious complications should involve multi-disciplinary support.

Practice points  EUS, both diagnostic and guided FNA, are extremely safe outpatient procedure.  Adverse events associated with EUS and EUS-FNA, though rare, include perforation, bleeding and infection.  EUS-FNA of solid masses can be performed in patients taking aspirin or NSAIDS, but not in patients taking clopidogrel or anticoagulants.  Prophylactic antibiotics are not required for EUS-FNA of solid lesions.  For EUS guided Celiac Plexus Neurolysis, patients should receive adequate intravenous hydration peri-procedure to reduce orthostatic hypotension.  EUS is safe, effective and method of choice to drain upper GI peri-luminal pancreatic fluid collections (PFC), using either multiple plastic or wide caliber bi-flanged dedicated metal stent.  Complications associated with EUS guided drainage of PFC include -perforation, bleeding, infection and migration of stent.  EUS guided pancreatic duct drainage, is one of the most technically demanding EUS intervention, associated with high technical failure and complications (perforation, bleeding, pancreatitis, fever, pancreatic duct leak and post-procedure pain).  Complications associated with EUS-BD are related to route of entry (trans-gastric or transduodenal), type of devices used, stage or extent of disease and experience of the operator.  Complications associated with EUS-BD include, bile leak & bile peritonitis, perforation, bleeding, and pneumo-peritoneum.

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Research agenda  Pancreatic fluid collection: comparison in technical success, duration of procedure, clinical success, re-interventions, overall outcome, and complications are required in EUS guided drainage of pancreatic fluid collection using plastic or dedicated metal stent in (a) pseudocyst and (b) WON.  EUS-BD: direct comparison of EUS-CDS versus EUS-HGS in malignant distal biliary obstruction patients with failed ERCP for: technical success, complications, stent patency and jaundice free survival.  EUS-BD versus PTBD, in patients with failed ERCP, with direct one-step SEMS placement. To evaluate: technical success, time to complete the procedure, complications, QOL, long term stent patency and jaundice free survival.  EUS-BD versus ERCP, in intervention nay¨ve patients, with direct one-step SEMS placement. To evaluate: technical success, time to complete the procedure, complications, QOL, long term stent patency and jaundice free survival.

Conflict of interest The author reports no direct financial interests that might pose a conflict of interest in connection with the submitted manuscript.

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