Background

EUS-guided cholangiopancreatography was first described in 1996. Using a curved linear array (CLA) echoendoscope, a standard fine-needle aspiration (FNA) needle is guided under real-time visualization into the bile or pancreatic duct and contrast injected for cholangiopancreatography or pancreatography. The route of access is anterograde, in contrast to the retrograde approach of ERCP. The authors prefer the term EUS-guided anterograde cholangiopancreatography (EACP) to cover the spectrum of EUS-guided techniques for accessing and draining the bile and pancreatic ducts ( Box 2 ). Patients with known difficult anatomy (eg, altered anatomy or gastric outlet obstruction) or prior failed ductal access are more likely to require EACP. All patients referred for therapeutic ERCP should be consented for both ERCP and EACP to allow same-session EUS-guided drainage when ERCP fails.

There are theoretic advantages of EACP over ERCP. By avoiding the ampulla and accidental cannulation or injection of the pancreatic duct, EACP eliminates the risk of pancreatitis. EACP is reserved for failed ERCP but could eliminate the problem of difficult cannulation altogether if used as a primary access strategy. Anterograde transenteric drainage can obviate all instrumentation (wire passage, dilation, and stenting) of the downstream stricture. Additionally, creating a natural fistula at a distance from the obstructing tumor resolves the problem of tumor ingrowth and overgrowth, which can cause stent obstruction.

Background

EUS-guided cholangiopancreatography was first described in 1996. Using a curved linear array (CLA) echoendoscope, a standard fine-needle aspiration (FNA) needle is guided under real-time visualization into the bile or pancreatic duct and contrast injected for cholangiopancreatography or pancreatography. The route of access is anterograde, in contrast to the retrograde approach of ERCP. The authors prefer the term EUS-guided anterograde cholangiopancreatography (EACP) to cover the spectrum of EUS-guided techniques for accessing and draining the bile and pancreatic ducts ( Box 2 ). Patients with known difficult anatomy (eg, altered anatomy or gastric outlet obstruction) or prior failed ductal access are more likely to require EACP. All patients referred for therapeutic ERCP should be consented for both ERCP and EACP to allow same-session EUS-guided drainage when ERCP fails.

There are theoretic advantages of EACP over ERCP. By avoiding the ampulla and accidental cannulation or injection of the pancreatic duct, EACP eliminates the risk of pancreatitis. EACP is reserved for failed ERCP but could eliminate the problem of difficult cannulation altogether if used as a primary access strategy. Anterograde transenteric drainage can obviate all instrumentation (wire passage, dilation, and stenting) of the downstream stricture. Additionally, creating a natural fistula at a distance from the obstructing tumor resolves the problem of tumor ingrowth and overgrowth, which can cause stent obstruction.

Echoendoscopes

Standard CLA echoendoscopes are commercially available with 2 channel sizes: small (standard) and large (therapeutic). The therapeutic CLA echoendoscope with a channel of 3.7 or 3.8 mm enables the passage of accessories of up to 11F. The forward-view CLA scope, which has overlapping endoscopic and EUS fields, has a 3.7-mm channel. Accessories exit along the same axis as the echoendoscope, enabling direct visualization of the accessory as it exists the channel, similar to a standard gastroscope. A potential drawback of the scope is the lack of an elevator to facilitate stent insertion and to clamp down on a guidewire during over-the-wire exchanges.

Fine-Needle Aspiration Needles for Ductal Access

A conventional FNA needle can be used to access the bile or pancreatic duct. The choice of needle size depends on the clinical context, the goal of the procedure, and the ductal anatomy. Most operators use a 19-gauge (G) needle, through which a 0.035-in, 400 to 450 cm long wire can be inserted. The drawback of the 19-G needle is its relative stiffness, which results in a very tangential angle of puncture. The elevator, when activated, has virtually no effect on the puncture angle. It is also difficult to penetrate indurated tissue with the 19-G needle. Modified blunt-tipped access needles may avoid inadvertent shearing of the wire on the bevel of the needle. The 22-G needle has greater flexibility, but it only accepts an 0.018-in guidewire, which lacks the stability and trackability required for over-the-wire intervention. The 0.018-in wire is also hard to steer and see on fluoroscopy. The 22-G needle may be preferred when targeting a nondilated duct (eg, intrahepatic or pancreatic) or when puncture with the 19-G fails. The 0.018-in wire may need to be exchanged for a 0.035-in wire through a catheter. A 25-G needle does not accept a wire, but it might be considered when the goal is a diagnostic cholangiogram or pancreatogram, especially in a patient with a coagulation disorder or low platelet count. Injection of saline may distend the duct making access with a larger needle easier. An alternative to using the FNA needle to achieve ductal access is the diathermic needle knife with removable inner needle (Zimmon needle knife, Cook Medical, Bloomington, IN, USA). Pure cutting current is applied during puncture to penetrate tissue. The advantage of using the needle knife is the ability to immediately exchange the inner needle for a guidewire. A drawback of the needle knife is the limited visibility of only the needle at the catheter tip, both on ultrasound and fluoroscopy. Another drawback is the risk of diathermy trauma to tissue. Although a continuous stainless steel needle will maintain the predicted trajectory path as it is advanced, the more flexible needle knife catheter may veer off axis into a neighboring structure, which may be a major vessel.

Guidewires

The guidewires used in EACP are the same as those used in ERCP. The authors routinely start with the 0.035-in hydrophilic Glidewire (Terumo, Somerset, NJ) inserted through a 19-G needle. As in ERCP, the hydrophilic Glidewire has excellent steerability to negotiate tortuous ducts and high-grade strictures. The low coefficient of friction, however, is a drawback for over-the-wire exchange of accessories. During the rendezvous procedure, extreme care must be taken that the Glidewire does not slip back during the withdrawal of the echoendoscope and insertion of the duodenoscope. One can exchange the Glidewire through a standard ERCP catheter for a stiffer instrumentation wire, but this requires advancement of the catheter across the bowel lumen and obstruction. A 22-G needle will only accept a 0.018-in guidewire, but this is very limited by the lack of stability and trackability required for over-the-wire intervention. In the United States, the hydrophilic Glidewire is only available in a 0.020-in size, which creates too much friction within the 22-G needle. Manufacturers have modified guidewires in various ways (reduced diameter, longer flexible hydrophilic tips, stiffer instrumentation shafts) to obviate wire exchanges.

Stents

The choice of stent type, size, and length depends on the ductal anatomy. Again, as in ERCP, straight and pigtail plastic stents or self-expandable metal stents (SEMS) can be used. Pigtail stents minimize the risk of stent migration (especially into the duct), but the pigtail end makes stent insertion more difficult owing to a weakened coaxial transfer of force. The authors, therefore, prefer to use straight stents for transenteric drainage, which also allows stent retrieval or exchanging the stent over the wire without loss of ductal access. Covered SEMS have been used for transenteric drainage but may migrate, particularly with shortening. The covering may block drainage of a secondary duct (eg, cystic duct or intrahepatic branch). Uncovered SEMS are generally unsuited for transenteric drainage because of leakage between the struts. Uncovered SEMS can be placed in exchange for a temporary plastic stent after the fistula tract has matured. The authors always use SEMS when a malignant stricture can be traversed and drained downstream. This practice is justified because plastic stent clogging is likely to require a repeat EACP procedure.

More recently, specialized stents have been developed for specific purposes in transenteric drainage (see section “Lumen-apposing transluminal stent”). These stents create a lumen-apposing transenteric anastomosis to allow secure leak-free drainage and through-the-stent endoscopic interventions.

Transpapillary Rendezvous Procedure (Anterograde Access and Retrograde Drainage)

The rendezvous procedure is derived from the percutaneous technique whereby a guidewire is passed anterograde across the stricture and papilla (or surgical anastomosis) for subsequent rendezvous retrograde drainage by ERCP ( Fig. 1 ). The rendezvous procedure is limited by 2 requirements: (1) an endoscopically accessible papilla (or bilioenteric anastomosis) and (2) successful passage of the guidewire across the stricture into the downstream small bowel. Traditional percutaneous access under fluoroscopic guidance is substituted for transgastric or transduodenal access under EUS guidance. This procedure minimizes the role of interventional radiology and should be considered an advanced cannulation technique for ERCP. More than 300 cases of successful EUS-guided rendezvous procedures performed for pancreatobiliary obstructions have been reported in the literature ( Table 1 ). Success rates vary between 35% and 98% in the largest cases series. EUS-guided puncture of the duct and ductography are accomplished in most cases. Failure is mainly caused by the inability to steer a guidewire across the stricture. Rescue upstream transenteric drainage can be performed to drain the obstructed duct. When combining attempted EUS-guided rendezvous and upstream drainage in cases of failure, the overall drainage success rate is 87%. The reported complication rates are 12% to 22% and include bile leaks, self-resolving pneumoperitoneum, subcapsular hematoma, and postprocedural pancreatitis.

An 81-year-old woman presented with painless jaundice and imaging concerning for a pancreatic mass. An EUS was performed, which demonstrated a mass in the pancreatic head. FNA was diagnostic for adenocarcinoma. An ERCP was attempted; however, despite multiple attempts including a precut sphincterotomy, deep cannulation could not be achieved. The patient subsequently underwent an EUS-guided rendezvous procedure. ( A ) Left intrahepatic puncture with a 19-G needle ( arrow ) under EUS guidance. ( B ) 0.035-in guidewire passed anterograde through the needle ( arrow ), across the obstruction and into the duodenum. ( C ) Capture of the guidewire ( arrow ) by a duodenoscope. ( D ) Stent catheter ( arrow ) placed into the bile duct. ( E ) 10 mm × 6-cm self-expandable metal biliary stent partially deployed ( arrow ). ( F ) Fully deployed stent ( arrow ).

Anterograde Access and Downstream Transductal Drainage

This strategy is derived from percutaneous internal stent drainage performed by interventional radiologists. The prerequisite for downstream drainage is the successful traversal of the obstruction with a guidewire. The authors have reported a series of 5 patients who underwent anterograde biliary SEMS placement because of nontraversable high-grade duodenal strictures (n = 4) and an endoscopically unreachable hepaticojejunostomy (n = 1). The SEMS was successfully deployed with a decrease in bilirubin levels in all cases. No postprocedural complications were noted after a median follow-up of 9.2 months. Puspok and colleagues have previously described a successful EUS-guided transhepatic SEMS in a single patient with a malignant biliary obstruction following gastrectomy and Roux-en-Y anastomosis. Bories and colleagues successfully placed a SEMS transhepatically and under EUS guidance in 2 patients. However, these procedures were performed in a 2-stage fashion with initial creation of a hepaticogastrostomy tract followed by anterograde placement of a SEMS in a second separate procedure.

The authors’ success with anterograde drainage for malignant obstruction has led them to apply a similar approach for benign disease. An alternative to ERCP is particularly attractive in post–gastric bypass patients harboring biliary stones. Hurdles to successful ERCP include the need for deep enteroscopy to reach the ampulla, difficult bile duct cannulation using a forward viewing scope, and limitations imposed by a longer length and smaller channel size of the enteroscope. The authors reported technical success of EUS-guided anterograde balloon sphincteroplasty and anterograde stone extraction in 4 out of 6 patients. Park do and colleagues have described a case report of EUS-guided transhepatic anterograde balloon dilation for a benign bilioenteric anastomotic stricture. The available data on EUS-guided downstream transductal interventions are summarized in Table 2 .

Table 2

Anterograde access and downstream transductal drainage

	No. of Cases	Puncture and Dilatation Device	Stent Placed	Technical Success (%)	Clinical Success (%)	Complications
Nguyen-Tang et al, 2010	5	19-G needle	SEMS	100	100	None
Park do et al, 2012	1	19-G needle	Anterograde stricturoplasty	100	100	None
Weilert et al, 2011	6	19-G needle	Anterograde sphincteroplasty	67	67	Subcapsular hematoma (1)
Artifon et al, 2011	1	19-G needle	SEMS	100	100	None
Shah et al, 2012	16	19-G needle	SEMS, anterograde sphincteroplasty	81	81	Hepatic hematoma
Iwashita et al, 2013	7	19-G needle	Anterograde sphincteroplasty SEMS	86	86	Adverse events (2)
Park do et al, 2013	14	19-G needle	—	57	57	None
Weilert, 2014	7	19-G needle	SEMS/anterograde sphincteroplasty	86	86	Bile leak (1)
Saxena et al, 2014	2	19-G needle	SEMS	100	100	None

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