Therapeutic endoscopic ultrasound: rationally progressing

In 1997, Gerolami et al. published a case series of four patients wherein the clinical value of endoscopic ultrasound (EUS) in guiding the decision to perform endoscopic drainage was clearly demonstrated [1]. On the one hand, EUS could clearly identify intervening blood vessels in the gut wall and establish a clear contraindication to endoscopic drainage of a pseudocyst with intraluminal bulging. On the other hand, for cases of pseudocysts without an intraluminal bulge, EUS was useful in establishing the feasibility of endoscopic drainage and identifying the site of puncture. In this paper, a radial echoendoscope was used and therefore real-time guidance of the entire drainage procedure could not be performed. Instead, after EUS had identified the optimum site of puncture, a biopsy forceps was inserted through the instrument channel of the echoendoscope and mucosal biopsies were taken at this site in order to mark out the location of the intended puncture site. The echoendoscope was then exchanged for a duodenoscope, which was used for the drainage procedure. Earlier, in 1992, Grimm et al. had demonstrated in their case report that a linear echoendoscope could be used to provide real-time guidance of endoscopic drainage, from initial needle puncture to guidewire insertion [2]. In those days, only a diagnostic linear echoendoscope with a 2 mm instrument channel was available, and hence a stent could not be inserted through the echoendoscope. The echoendoscope had to be exchanged for a duodenoscope for stent insertion. Soon after in 1998, Vilmann et al. published their experience using a prototype therapeutic linear echoendoscope with a larger instrument channel of 3.2 mm [3]. This allowed the insertion of an 8.5 Fr double-pigtail stent after needle puncture and guidewire insertion, without the need to exchange for a duodenoscope.

Since those early reports, therapeutic echoendoscopes with larger instrument channels of 3.7 – 4.0 mm have become commercially available (e. g. Olympus GF-UCT160-OL5, 3.7 mm; Fujifilm EG-580UT, 3.8 mm; Pentax EG-3870UTK, 3.8 mm and EG38-J10UT, 4.0 mm), and larger diameter stents can be inserted easily. EUS-guided endoscopic drainage has been clearly established as the first-line treatment option for symptomatic walled-off pancreatic collections. Randomized trials have highlighted the superiority of EUS-guided over non-EUS-guided endoscopic drainage of pseudocysts. Comparable efficacy to surgical cystogastrostomy has been demonstrated. Apart from simple transmural drainage of pseudocysts, EUS-guided drainage can now also be applied to all symptomatic intra-abdominal walled-off collections that are accessible endoscopically and for which no contraindications exist. Apart from achieving passive transmural drainage, a more aggressive approach to remove infected solid debris in patients with infected walled-off necrosis by additional endoscopic necrosectomy is now accepted as mainstream clinical practice. In these cases, after initial placement of double-pigtail plastic stents, if drainage and clinical response are inadequate, further balloon dilation of the transmural tract to 15 mm is performed and a gastroscope is inserted for endoscopic debridement [4].

In recent years, fully covered lumen-apposing metal stents (LAMS) such as the Axios stent (Boston Scientific, Marlborough, Massachusetts, USA) have been developed [5]. Compared with plastic stents, these stents have larger diameters when deployed, ranging from 10 mm to 20 mm. This facilitates not only the drainage process but also entry of an endoscope into a necrotic cavity for endoscopic necrosectomy without the need for further balloon dilation of the drainage tract. The hot Axios stent has a cautery wire at the tip of its insertion catheter, and stent insertion and deployment can be achieved easily under complete EUS guidance without fluoroscopy in a single step, without the need to use the Seldinger technique of initial needle puncture and guidewire insertion. Being lumen apposing, the Axios stent creates a robust and reliable conduit between nonadherent lumens around the gastrointestinal tract. Hence, there is potential for application beyond drainage of pancreatic fluid collections. The technique has been utilized for accessing and draining the gallbladder and biliary tract, as well as bypassing gastric outlet or duodenal obstruction by endoscopic gastrojejunostomy. In patients with Roux-en-Y gastric bypass, EUS-directed transgastric endoscopic retrograde cholangiopancreatography (ERCP) is being applied in research settings.

EUS has expanded and revolutionized endoscopic therapy. EUS has evolved from a purely diagnostic procedure to one that supports endoscopic interventions and now even directs EUS-guided interventions. In addition to confirming the appropriate indication and ensuring safety for endoscopic drainage, EUS has expanded the indications: drainage procedures have progressed from drainage of fluid collections to drainage of the pancreaticobiliary ducts, and from drainage of endoscopically nonbulging adherent fluid collections to drainage of nonbulging nonadherent collections. EUS-guided interventions have been transformed from complex time-consuming procedures requiring multiple endoscopes and accessories to a simpler time-saving procedure with the availability of a dedicated therapeutic echoendoscope and specialized accessories such as the hot Axios stent.

Even as the success story of EUS continues, critical reflection of its application in niche indications is essential. Evidence-based and cost-effectiveness data are crucial. EUS and ERCP are two complementary endoscopic procedures that may potentially become partly competitive. The pancreaticobiliary endoscopist must be skilled in both therapeutic EUS and ERCP. This will ensure the most efficient and comprehensive treatment decision and approach.

Fig. 1 Therapeutic endoscopic ultrasound (EUS) could be considered as one of the major breakthroughs in endoscopy since its inception about 25 years ago. a The graphic shows a variety of pathological processes that may be treated with therapeutic EUS techniques. These include, but are not limited to: drainage of pancreatic pseudocysts and necrosis, drainage of subdiaphragmatic, retroperitoneal and pelvic abscesses and collections, transgastric bile or pancreatic duct stent placement, and enteral anastomosis. b The essential steps to drain a pancreatic fluid collection are shown in this panel. c The key accessories in interventional EUS are needles, wire, balloon and plastic or self expanding stents. Of course, any accessory such as catheters, snares and baskets that can be advanced through the working channel of the EUS scope may be used to deal with various types of gastrointestinal pathologies. Illustration: Michal Rössler. Figure design and legend: Klaus Mönkemüller.

• References

• 1 Gerolami R, Giovannini M, Laugier R. Endoscopic drainage of pancreatic pseudocysts guided by endosonography. Endoscopy 1997; 29: 106-108
• 2 Grimm H, Binmoeller KF, Soehendra N. Endosonography-guided drainage of a pancreatic pseudocyst. Gastrointest Endosc 1992; 38: 170-171
• 3 Vilmann P, Hancke S, Pless T. et al. One-step endosonography-guided drainage of a pancreatic pseudocyst: a new technique of stent delivery through the echo endoscope. Endoscopy 1998; 30: 730-733
• 4 Seewald S, Ang TL, Teng KY. et al. Endoscopic ultrasound-guided drainage of abdominal abscesses and infected necrosis. Endoscopy 2009; 41: 166-174
• 5 Binmoeller KF, Shah J. A novel lumen-apposing stent for transluminal drainage of nonadherent extraintestinal fluid collections. Endoscopy 2011; 43: 337-342