Endoscopic ultrasound-guided gallbladder drainage for acute Should the endoscopic option become the status quo?

Authors: Robert Sean O'Neill, Timothy Walter, Christina Lee, Kevin Jia, Ian Turner, George Ermerak, Paul Edwards, David Abi-Hanna, Milan Bassan, Cynthuja Thilakanathan

Abstract

Acute cholecystitis is a common surgical condition characterised by inflammation of the gallbladder wall, commonly secondary to cystic duct or infundibulum obstruction. The disease can be complicated by infection secondary to translocation of bacteria from the bile duct resulting in significant patient morbidity and potential mortality. The gold standard of treatment is cholecystectomy, however endoscopic ultrasound-guided gallbladder drainage (EUS-GBD) has emerged over the past two decades as a minimally invasive technique for gallbladder decompression in patients deemed to be high surgical risk candidates, with reduced surgical interventions, adverse events and unplanned hospital admissions compared to percutaneous gallbladder drainage. The aim of this review is to outline the procedural components of EUS-GBD, the clinical and technical outcomes, complications and future directions.

Core Tip: Endoscopic ultrasound-guided gallbladder drainage (EUS-GBD) is a minimally invasive technique that has emerged in the management of acute cholecystitis (AC) with attractive technical and clinical success rates. Increased adoption at a global scale has seen it surpass percutaneous gallbladder drainage given the reduced morbidity associated with the procedure. Although EUS-GBD is limited to those with AC, there is emerging data supporting its use in a range of biliary pathologies including malignant biliary obstruction. Despite its perceived role as a destination therapy, more recent literature has demonstrated that cholecystectomy can be safely and successfully performed post EUS-GBD. With increased adoption of EUS-GBD it is envisioned that it will become standard practice in those in whom cholecystectomy is not deemed an option.

INTRODUCTION

Acute cholecystitis (AC) is a common surgical emergency with an increasing incidence globally. The current standard of care of management of AC is laparoscopic cholecystectomy (LC). However, due to an ageing population globally with increased frailty and burden of comorbidities, the incidence of patients deemed to be poor surgical candidates has also increased. Percutaneous transhepatic-GBD (PT-GBD) has often been performed in patients deemed to have significant surgical risk and can also be used as a bridge to cholecystectomy, however this procedure is commonly associated with pain, poor quality of life, longer hospital stay, increased reintervention and readmission rates, and issues with drain-occlusion[1,2]. Although PT-GBD is recognised as a method for biliary decompression in AC in poor surgical candidates, there has been a shift to identify a more permanent solution in these patients that is associated with reduced morbidity.

Innovations in therapeutic endoscopic ultrasound (EUS) have allowed therapeutic interventions to be performed in patients in whom surgical intervention was deemed to be high risk due to significant associated morbidity and mortality. Globally, this has led to increased adoption of this technique in specialized centres with improved outcomes for these patients. EUS-guided gallbladder drainage (EUS-GBD) is an emerging area in therapeutic endoscopy that offers definitive non-operative management of AC. The procedure involves the creation of a fistulous tract between the gallbladder and the gastrointestinal tract lumen (cholecystogastrostomy or cholecystoduodenostomy) using plastic or metal stents. The initial approach for EUS-GBD, published in 2007, used double pigtail plastic stents for gallbladder drainage[3]. There has since been increasing adaptation of the technique with improved outcomes and reduced complications. This is partly attributed to improved techniques as well as innovations in stent design, with there being a shift away from double pigtail plastic biliary stents followed by self-expanding metal stents (SEMS) and to the use of lumen apposing metal-stents (LAMS). Since its inception, the updated Tokyo guidelines for AC introduced EUS-GBD as a therapeutic option in those affected by grade 2 and 3 AC whom are deemed to be poor surgical candidates[4]. The procedure has been demonstrated previously to be associated with a reduced reintervention rate, lower post-procedural pain scores and analgesic requirements, reduced adverse events, and reduced unplanned hospital admissions when compared to PT-GBD which is often deemed to be the second-line therapy in those whom surgery is not deemed to be a viable option for AC[3,5,6]. Although a definitive option in those whom are not deemed to be surgical candidate, EUS-GBD does not completely preclude surgery, and cholecystectomy can still be performed in specialized units. Although the majority of evidence for EUS-GBD has focused on the management of AC, EUS-GBD also has demonstrated efficacy in the management of distal malignant biliary obstruction in the setting of failed endoscopic retrograde cholangiopancreatography (ERCP) in low survival patients. In the absence of a safe window for EUS-guided bile duct drainage after failed ERCP, there is emerging evidence to suggest that EUS-GBD with LAMS should be considered as an early approach in these patients given impressive technical and clinical success rates with a low adverse event profile[7].

This review will aim to focus on the procedural components of EUS-GBD, the technical and clinical outcomes associated with EUS-GBD, associated complications and the future directions of EUS-GBD.

EUS GUIDED GBD – PROCEDURAL COMPONENTS

Pre-procedural considerations

The first consideration prior to proceeding with EUS-GB drainage is to assess for contraindications. EUS-GB drainage should not be performed in cases of gallbladder perforation, biliary peritonitis, large-volume ascites or significant coagulopathy and intolerance to anaesthesia. Cross-sectional imaging should then be reviewed to determine whether the gallbladder is dilated, a safe window is present for LAMS placement, the best endoscopic approach (transgastric vs transduodenal) along with a rescue plan in the event of adverse events (Figure 1).

Endosonographic assessment

The gall bladder is then assessed with EUS using a curved linear array oblique-viewing therapeutic echoendoscope. The gall bladder is usually identified from the gastric antrum or duodenal bulb and often the approach with the safest window is used. The safest window is determined Absence of any vessels (using colour flow Doppler imaging) or vital structures between the enteric lumen and the gallbladder, short distance between the gallbladder and the enteric lumen (wall thickness), and a long runway. The ideal distance between the gall bladder lumen and enteric lumen is a wall thickness off < 10 mm so that the LAMS stent (usually a 10 mm × 10 mm LAMS or a 15 mm × 10 mm LAMS) can appose both walls tightly together with reduced likelihood of bile leak. The runway should often be at least 20 mm to accommodate the deployment of a 10 mm × 10 mm LAMS stent with a shorter runway running the risk of stent misdeployment. Where there is a safe window present with long runway and short wall thickness, EUS-GB drainage does not require fluoroscopy. However, where a difficult procedure is predicted (previous percutaneous cholecystostomy, short runway, non-dilated gallbladder), then fluoroscopic guidance will be required.

The gallbladder neck is targeted due to its fixed position and proximity to the duodenal bulb in the case of cholecystoduodenostomy formation, while the gallbladder body is more favorable when targeted from the gastric antrum in the formation of a cholecystogastrostomy[8,9]. The gallbladder should also be carefully evaluated for abnormal wall thickening or the presence of an intraluminal mass which could complicate the procedure. In addition, both the duodenal and gastric mucosa should be inspected for ulceration, erosions or malignancy as this could impair stent placement and procedural success.

Transgastric vs transduodenal approach

With regards to the preferred site of puncture, there is no data demonstrating superiority of either the transgastric or transduodenal approach from both a technical and clinical success standpoint. The duodenum has the advantage of being a fixed structure with a close proximity to the gallbladder neck resulting in reduced risk of stent migration. The echoendoscope position is also in a more long stable position in the duodenal bulb making it technically easier for LAMS deployment. The duodenum is less affected by peristalsis compared to the distal stomach with theoretical reduced likelihood of food reflux and food impaction[10,11]. The transgastric approach on the other hand is preferred in selected patients for potential cholecystectomy in the future, however, due to thicker gastric wall layers and due to stronger peristaltic forces, the transgastric approach has a higher risk of buried stent syndrome[12]. The published literature demonstrates no significant difference in technical or clinical success between the transgastric and transduodenal route, however the rate of adverse events has been demonstrated to be higher in the transgastric route (27.5% compared to 15.2%), however this was not statistically significant[13]. In the case of recurrent cholecystitis post EUS-GBD, surgery can be a more complex procedure hence optimal approach should be discussed with surgical colleagues in patients where EUS-GBD has been performed as a bridge to cholecystectomy[14,15].

LAMS and co-axial plastic stent placement

Once a safe window is identified, the next step will be stent placement. In terms of stent deployment, the LAMS can be deployed over a wire or using freehand technique, with the latter approach being most commonly used where a safe window is present. With the freehand approach, a safe window with a long runway is identified. The size of the LAMS will be based on the length of the runway and the gallbladder wall thickness with preferred sizes being either the 10 mm or 15 mm diameter stent. In addition, if a patient is likely to require repeat gastroscopy with cholecystoscopy through the LAMS to remove the stones at a later stage, then the 15 mm diameter stent is preferred. However, the 10 mm LAMS can still be used and dilated using controlled radial expansion balloon to enable gastroscope passage through the stent to perform stone removal. The LAMS deploying device is passed through the working channel of the therapeutic echoendoscope until the tip can be visualised sonographically abutting the enteric lumen. In the case of AXIOS (Boston Scientific, Marlborough, Massachusetts, United States), using electrocautery (auto cut current), the electrocautery tip punctures through the enteric wall and gall bladder wall into the gallbladder lumen. This will be visualised sonographically and confirmed when bubbling is seen (Figure 2A). The electric current is then disconnected. Once the sheath is in the gallbladder lumen, it is advanced until there is a suitable length runway for the distal flange to be deployed. The distal flange is then deployed under sonographic guidance (Figure 2B). Once deployed, the stent is pulled back so the distal flange sits tightly (and slightly tented) against the gallbladder wall. The endoscopic view is then used to deploy the proximal flange (Figure 3A). Bile should flow immediately once deployed. Tissue overgrowth and stent stabilization is then aided through the insertion of a co-axial double pigtail plastic stent (over the wire) through the LAMS. This is also thought to reduce the likelihood of gallbladder mucosal abrasion, along with reduce the likelihood of LAMS stent occlusion where large gallstone are present[14,16,17]. Sometimes, controlled radial expansion balloon dilatation of the LAMS can also be performed to expedite gallbladder drainage (Figure 3B)[18].

The over-the-wire technique for LAMS deployment is considered in cases where a difficult case is predicted. This technique involves passing a 19-G EUS fine aspirate needle through the enteric wall into the gall bladder lumen under sonographic guidance. After the stylet of the needle is removed, to confirm correct needle tip position, bile is aspirated (approximately 2-3 mL). Under fluoroscopic guidance, contrast medium can be injected through the needle into the gallbladder to also confirm placement. In the setting of a non-dilated gallbladder, the gallbladder can be distended by injecting fluid normal saline to provide a longer runway for stent deployment. Once placement is confirmed, a 0.025- or 0.035-inch guidewire is passed through the needle and coiled into the gallbladder under fluoroscopic guidance. The LAMS deploying system is then passed over the wire until it reaches the enteric wall. Electrocautery is then used to pass the device through the enteric lumen into the gall bladder lumen. Where non-cautery method for LAMS deployment is being considered, the tract is first dilated using either a bougie, tapered tip balloon dilator or 6-Fr cystotome (electrocautery required)[8,19]. The LAMS can then be passed over the wire into the gall bladder lumen and distal flange deployed followed by proximal flange in the enteric lumen.

Type of stent

LAMS use is currently recommended by the American Gastroenterological Association, particularly in EUS-GBD, given it can be deployed using a single-step EUS-guided LAMS delivery system. This is a result of reduced risk of adverse events associated with LAMS (9.9%) compared to SEMS (12.3%) and plastic stents (18.2%), despite all possessing a pooled clinical and technical success rate of greater than 90%.

With regards to stent design and implementation, different LAMS systems have been developed with varying lengths and diameters. The most commonly utilised LAMS systems for GBD are the AXIOS stent (Boston Scientific, Marlborough, Massachusetts, United States), and the Spaxus stent (Taewoong Medical Co, Gimpo, Korea), while the Nagi stent (Taewoong Medical Co Ltd, Gimpo, South Korea) is less commonly utilised. The Spaxus stent has larger flanges, an adjustable interflange distance and longer length, leading to a postulated reduced risk of adverse events and perceived easier use. Although theoretically the Spaxus stent has features that should translate to improved technical success with reduced adverse events, there is varying efficacy and safety of the AXIOS and Spaxus stents for both EUS-GBD and biliary drainage[20,21]. Singh et al[22], performed a systematic review and meta-analysis indirectly comparing LAMS for EUS-GBD and biliary drainage. The review included 18 studies of which 11 analysed the AXIOS LAMS compared to 7 for the Spaxus LAMS. With regards to EUS-GBD, the pooled technical and clinical success using the AXIOS stent was 96.2% and 92.7% respectively, with an adverse event incidence of 23.6%. With regards to the Spaxus stent, technical success was reduced marginally to 95.9% while clinical success was 94.2%. Notably, pooled adverse event analysis demonstrated that the incidence of total adverse events was lower in the Spaxus stent group compared to the AXIOS stent, with an incidence rate of 9.5%[22,23]. The large discrepancy in adverse event incidence between stent types is hypothesized to be secondary to stent design as well as the small number of studies utilized to calculate the pooled adverse event incidence. In addition to this, it is also postulated that due to the earlier adoption of the AXIOS stent when EUS-GBD was in its infancy as a technique, endoscopists have had time to refine their technique thus translating to reduced adverse events upon Spaxus stent introduction.

Stent diameter

Stent diameter is a crucial component of EUS-GBD as stent patency dictates risk of recurrence in patients with AC. The most common LAMS utilized in the case of EUS-GBD have a saddle length of 10 mm and 15 mm, with inner diameters of 10 mm, 15 mm, and 20 mm, with bilateral anchor flanges of 21 mm, 24 mm, and 29 mm[24]. Theoretically, a larger stent diameter can provide long term stable drainage to small calibre stents utilized in EUS choledochoduodenostomy[25]. In addition to this, larger stent diameter is associated with a reduced risk of bile leak and also permits access to the gallbladder in the event where treatment of cholelithiasis is required[10].

Follow-up post EUS-GBD

Post EUS-GBD, peroral cholecystoscopy can be performed at 4-6 weeks post index procedure to achieve stone clearance[26]. At the time of cholecystoscopy, the LAMS can be exchanged for double pigtail plastic stents to ensure fistula patency. Alternatively, in those patients who possess significant comorbidities in which repeat procedures prove to be undesirable, the LAMS can be permanently left in situ with 3-year stent patency reported at 86% with a delayed adverse event rate of 7.1%[27]. In those patients whom proceed to cholecystectomy post EUS-GBD, although adoption has been slow, recent data has demonstrated that EUS-GBD has a significantly shorter interval between gallbladder drainage and cholecystectomy, shorter survival procedure times and shorter length of stay for cholecystectomy compared to PT-GBD. In addition to this, the rate of conversion from laparoscopic to open cholecystectomy was not influenced by EUS-GBD[28]. Meta-analysis data encompassing 15 studies has demonstrated successful interval cholecystectomy post EUS-GBD, with the procedure being performed 32.9% of patients with a pooled adverse event rate of 13.2% without any procedure-related mortality[29].

EUS-GUIDED GBD – TECHNICAL AND CLINICAL OUTCOMES

With innovation in the field of EUS-GBD there has been a growing body of evidence particularly in the technical and clinical outcomes associated with the procedure. Numerous studies over the past 18 years have reported on both the technical and clinical success of EUS-GBD with variation in results. Technical success of EUS-GBD varies from 84.6% to 100%, while clinical success is also high, ranging from 86% to 100%. Meta-analysis data encompassing 233 patients across 12 studies utilising LAMS in high risk surgical patients with cholecystitis or malignant biliary obstruction demonstrated pooled technical and clinical success rates of 94% and 93% respectively[30]. Although the established technical and clinical success rate of EUS-GBD make it an attractive modality for the management of AC in high surgical risk patients, complications can still arise. This has however improved over time with improved technique along with device optimization especially when performed in centers with high expertise. Meta-analysis data demonstrated pooled adverse events rates of 17.9%, however, bleeding rates and infection rates have been reported as low as 0.8% and 0.86% respectively[31,32]. A detailed description of studies reporting on the technical and clinical success rates of EUS-GBD is presented in Table 1[5,6,27,33-71]. Although the mortality rate in patients undergoing EUS-GBD is relatively high, this is likely reflective of patient selection rather than the procedure itself, with those patients undergoing EUS-GBD more likely to have significant life-limiting comorbidities that prelude to a poor prognosis in the context of AC. Previous studies examining EUS-GBD have also demonstrated lower post-procedural pain scores compared to percutaneous drainage, further emphasising it as an attractive option from a patient perspective while also improving patient outcomes and translating to reduced hospital length of stay. Additionally, EUS-GBD has demonstrated clinical and technical success in cirrhotic patients as demonstrated by Garg et al[63] highlighting the expanding patient cohorts that may derive benefit from this procedure compared to PT-GBD.

With regards to its technical and clinical success, EUS-GBD has demonstrated comparable efficacy with a desirable adverse event rate compared to more established means of gallbladder decompression, these being PT-GBD and endoscopic transpapillary GBD (ET-GBD). EUS-GBD has the benefits of an internal fistula being formed and permanent placement. In addition to this, EUS-GBD has demonstrated comparable technical and clinical success to PT-GBD, while also reducing the rate of adverse events at one year, number of unplanned readmissions, rate of recurrent cholecystitis, and the rate of reintervention after 3 days. In addition to these desirable clinical outcomes, EUS-GBD also demonstrated reduced post-procedural pain scores[6]. The reduced incidence of adverse events in the EUS-GBD population compared to PT-GBD was also confirmed by Hayat et al[72], whom in their meta-analysis and systematic review, demonstrated a reduced rate of delayed adverse events post procedure. With regards to comparison of EUS-GBD to ET-GBD, meta-analysis data has demonstrated higher technical and clinical success in EUS-GBD compared to ET-GBD for AC with no significant difference in overall adverse events. In addition to this, there was a lower rate of recurrent cholecystitis in the EUS-GBD group[72,73]. Although there is limited evidence with no head-to-head trials, when comparing all three modalities together, EUS-GBD and PT-GBD have demonstrated the greatest likelihood of clinical and technical success, with EUS-GBD having the lowest risk of recurrent cholecystitis, along with the shortest length of hospital stay highlighting a potentially health economic benefit associated with the procedure[74]. In addition to this, EUS-GBD also has the added benefit of avoiding the risk of post-procedural pancreatitis which can eventuate in the case of ET-GBD[75].

Aside from patient and procedural related outcomes, EUS-GBD has also been demonstrated to have shorter procedure time and fluoroscopy exposure compared to ET-GBD highlighting an important aspect in occupational safety with regards to cumulative radiation exposure to procedural staff[76].

With reference to cost-effectiveness, previous studies have demonstrated that although EUS-GBD does save money in the context of reduced adverse event profile, the net budget impact of introducing EUS-GBD is higher compared to PT-GBD[77]. There is conflicting data however demonstrating that endoscopic gallbladder drainage is more cost effective in treating AC in poor surgical candidates compared to PT-GBD, however ET-GBD is favored over EUS-GBD from a cost perspective[78]. Ultimately further data is required in larger cohorts to determine whether there is a cost benefit, aside from its clinical benefit, to implementing EUS-GBD as ultimately the practice has to be sustainable from a health economics perspective.

COMPLICATIONS OF EUS-GBD

Although the current standard of care of AC is cholecystectomy, this carries the risk of standard surgical complications secondary to both LC and potentially open cholecystectomy. In the case of patients with increasing frailty and advanced comorbidities, the potential for peri and post-procedural related complications does pose a significant concern making EUS-GBD a preferable option. In terms of adverse events associated with EUS-GBD, periprocedural and postprocedural complications are of a wide range but occur infrequently[24]. Previous meta-analysis data has demonstrated a cumulative rate of procedure-related adverse events of 11%, however this has been reported to be as high as 17.9% in pooled adverse events rates, however this did not discriminate between the type of stent used (LAMS vs double pigtail plastic stent)[31,79,80].

Adverse events associated with EUS-GBD include stent migration (3.9%) and bile leak (4%), both of which are decreased through the use of LAMS with co-axial double-pigtail plastic stents. Stent misdeployment is a significant periprocedural adverse event with maintenance of access considered a key component of reintervention and salvage procedures[14]. With regards to the type of misdeployment, there are four main categories, these being (1) Complete proximal misplacement; (2) Distal flange misplacement; (3) Complete distal misplacement; and (4) Proximal flange misplacement. Armellini et al[81] reported an incidence rate of 3.4% of LAMS misdeployment, with misdeployment of the distal flange being the most commonly implicated. In terms of salvage therapy, reinsertion of a fully covered-SEMS through the LAMS lumen through a “stent-in-stent” strategy is the most commonly utilized technique in LAMS misdeployment. Although emergency surgery can be utilized in cases of LAMS misdeployment, it is rarely utilized if the “stent-in-stent” approach can be utilized to achieve gallbladder drainage.

In addition to this, stent dysfunction secondary to food impaction does pose an issue post LAMS placement in EUS-GBD, particularly in the case of gastric antral placement[9]. Infection rates post-procedurally vary between 0.85% and 3.8%[31,32]. However, this can often be managed with gastroscopy and clearance of obstruction or replacement of the co-axial double pigtail stent.

Other less common but significant adverse events associated with EUS-GBD include intestinal perforation, gallbladder perforation, bleeding, pneumoperitoneum and peritonitis secondary to stent migration[38,46,82]. Recurrent cholecystitis is a potential adverse event post EUS-GBD with previous studies reporting an incidence of approximately 5%. The main contributing factors for recurrent AC post EUS-GBD are stent dislodgement or occlusion (cholelithiasis, food impaction, blood or tissue overgrowth). In terms of management of recurrent AC post EUS-GBD, conservative measures can be implemented which usually involves intravenous antibiotic therapy, however repeat endoscopy with endoscopic debridement and pigtail stent insertion through the LAMS can be performed to facilitate appropriate gallbladder drainage[39,42]. Where recurrent cholecystitis occurs due to stone obstruction of the LAMS, cholecystoscopy with a gastroscope can be performed followed by stone extraction using standard endoscopic devices including basket device and rat-tooth forceps. In the setting where stones are large, stone fragmentation with electrohydraulic lithotripsy may be performed. Finally, post-procedural gastrointestinal bleeding is relatively uncommon and has been reported in 2.6% of patients undergoing EUS-GBD[83]. This usually responds with conservative management however endoscopic management or radiology guided embolization may be required.

FUTURE DIRECTIONS

With EUS-GBD emerging as an acceptable and minimally invasive non-surgical option for AC in therapeutic endoscopy centres, the focus has now shifted to what specific patient subsets may also benefit from this form of intervention. Its efficacy in patients with cirrhosis was initially pioneered by Jamwal et al[84] and was built upon by Garg et al[63], who, in an international multicentre retrospective review, demonstrated that EUS-GBD was technically and clinically effective, and possessed a desirable safety profile in patients with AC with diagnosed cirrhosis. Although this highlights a single subset of patients in whom EUS-GBD has demonstrated efficacy, further studies should aim to explore the outcomes of EUS-GBD in further patient subgroups.

The technique of EUS-GBD is another area in which further study is required. As previously mentioned, there is no data demonstrating superiority of either the transgastric or transduodenal approach from both a technical and clinical success standpoint. This is likely a reflection of small cohort sizes and as such does post a valid question that needs to be explored with more rigorous prospective studies.

Aside from patients diagnosed with AC, the role of EUS-GBD in patients with gallstone-related pathology has yet to be fully elucidated, particularly in those with gallstone related pancreatitis, cholangitis, choledocholithiasis and symptomatic cholelithiasis. With an ageing and comorbid population internationally, the prospect of a viable alternative that is minimally invasive and associated with high clinical and technical success certainly warrants further investigation. This was recently explored by Trieu et al[70], whom in a single centre study examined the role of EUS-GBD in biliary pathology (bile leak, choledocholithiasis, biliary colic, benign biliary stricture). Albeit the vast majority of patients included in the study underwent EUS-GBD for AC or choledocholithiasis, EUS-GBD did demonstrate technical success in cases of biliary pathology aside from AC. This again was recently validated by Riera Roig et al[85] who in their small retrospective study demonstrated that EUS-GBD has a role in both AC and non-AC pathology, with a technical and clinical success of 92.9% and 76.8% respectively. Future studies should aim to recruit larger patient cohorts in those diagnosed with biliary pathology separate to AC to determine whether EUS-GBD possesses similar technical and clinical success rates in those undergoing the procedure for AC. With further validation of the technique in non-AC related pathology, this should aim to increase the adoption of EUS-GBD as the standard of care for patients in whom cholecystectomy is deemed unsafe.

Although there is certainly enough data supporting the use of EUS-GBD in AC, hesitancy still exists in its adoption. This has been previously postulated to be secondary to a number of factors which were identified and expanded on by Villa[86]. These factors included heterogeneity on the definition of a “nonsurgical” patient; the idea that PT-GBD is an effective treatment as a bridge or destination therapy to cholecystectomy despite evidence revealing a higher postoperative mortality rate; readmission rate and length of hospital stay; a lack of awareness of the option of EUS-GBD; the perception that EUS-GBD could ultimately replace cholecystectomy and the lack of available expertise in EUS-GBD given it is a relatively innovative procedure in the field of natural orifice transluminal endoscopic surgery[87]. It is vital that in centres equipped to offer EUS-GBD, multidisciplinary case reviews are undertaken to identify patients in whom EUS-GBD would result in improved clinical outcomes. This has the capacity to improve individual patient morbidity and mortality, while concurrently providing an avenue in which there is shared decision-making regarding patient management in a collegiate manner. It is vital that patients are identified for EUS-GBD given its non-inferior clinical success rates compared to other non-surgical treatment modalities with superior adverse event profile. By identifying these patients, the appropriate standard of care is being upheld which ultimately correlates with improved patient outcomes from a morbidity and mortality perspective. In addition to this, further studies should aim to assess EUS-GBD from a cost perspective as ultimately it has to be an economically feasible procedure. There is limited evidence regarding cost analysis of EUS-GBD compared to percutaneous and other endoscopic approaches for gallbladder drainage. The perceived cost of the procedure may pose as a limitation for implementation in specific centres which suffer from significant financial strain. With the addition of antimigration devices, it is expected that procedural related costs will increase, however it is difficult not to justify this given the potential reduction in peri and post-procedural adverse events[80].

Competency analysis is another aspect of EUS-GBD which is limited in the literature. Despite the overwhelmingly positive technical success rates published in the literature, currently there is no standardized assessment of competency in EUS-GBD. It has previously been demonstrated that a predictor of unplanned procedural events and adverse events at 30 days is endoscopic experience of less than 25 EUS-GBD[5]. It is expected that with increasing adoption of the technique, a more standardized assessment of competency will ensue. In addition to this, clinician confidence is another aspect of EUS-GBD that should not be neglected. It should be noted that aside from assessing competency and technical success, clinician confidence in performing the procedure is paramount and as such, further studies should aim to evaluate this and determine where barriers exist in improving endoscopist procedural confidence.

Finally, the concept of EUS-GBD being a destination therapy for AC needs to be addressed. This is indeed not the case given cholecystectomy has been previously performed in patients whom have undergone EUS-GBD. Perhaps a lack of familiarity with the procedure has fostered a level of reluctance for surgeons to attempt cholecystectomy due to a perceived increased difficulty associated with the procedure along with the potential for peri and post-procedural complications. It should be noted that anaesthetic fitness is dynamic and as such, operative candidacy is fluid. With increased adoption of EUS-GBD it is foreseen that there will be increased frequency of cholecystectomy post-EUS-GBD in patients that improve clinically to warrant reassessment of surgical candidacy. With increased frequency it is hoped that there is increased familiarity with the procedure. In the event where this occurs, EUS-GBD may prove to be both a contemporizing measure as well as a destination therapy in patients with AC.

CONCLUSION

With an ageing and increasingly comorbid population, there is a continual push to innovate in all areas of medicine, particularly in the procedural domain. Endoscopy is not exempt from this, and the past two decades have seen significant advances in the field, particularly in the field of therapeutic EUS. Although the concept of EUS is not new, EUS-GBD has emerged as an exciting new minimally invasive endoscopic method through which AC can be treated in those patients whom aren’t deemed to be a surgical candidate. This method provides a definitive means through which AC can be managed with impressive technical and clinical success rates, along with a modest adverse event profile and low incidence of AC recurrence and reintervention rates. In addition to AC, EUS-GBD has also gained traction as an established method of biliary decompression in MBO, along with other biliary pathologies including biliary colic and choledocholithiasis. Although there is increasing evidence in support of this technique in the management of AC, adoption has been variable, with reasons for delayed uptake not limited to a lack of understanding of the procedure and a lack of a consensus definition of a ‘non-surgical candidate’. With an increased understanding of the therapeutic role of EUS-GBD, there needs to be a shift in the management of AC. Evidence suggests that PT-GBD, a previously tried and tested method for GB decompression in AC prior to cholecystectomy, is inferior to EUS-GBD with regards to length of stay and recurrence of AC. PT-GBD has often been favored over EUS-GBD due to the potential for surgery post PT-GBD, however this doctrine is being challenged with cholecystectomy being performed post EUS-GBD. In conclusion, EUS-GBD is an extremely attractive endoscopic modality for AC and should be considered the status quo in those in whom up front surgery for AC is not an option.