Endoscopes, Guidewires, and Accessories

Side-Viewing Endoscopes

Modern duodenoscopes are side-viewing video endoscopes equipped with an elevator. They are routinely used for diagnostic and therapeutic ERCP procedures. The elevator facilitates cannulation of the papilla and placement of accessories ( Fig. 4.1 ), whereas the large-diameter working channels of therapeutic duodenoscopes (4.2 and 4.8 mm) allow passage of large-bore (10 to 11.5 Fr) accessories. The improved technology has allowed most current ERCP endoscopes to have a large “therapeutic” channel without increasing the size of the insertion tube—similar to what was formerly referred to as “diagnostic” ERCP scopes. Smaller outer shafts of 7.4-mm-diameter pediatric duodenoscopes with a 2.2-mm channel are available for use in neonates (see Chapter 29 ). Unfortunately, the small working channel of such pediatric endoscopes limits their use to mostly diagnostic purposes and limited therapeutics such as stone extraction, while requiring smaller, dedicated accessories. In general, the standard adult duodenoscope can be used in most children aged above 2 years. A jumbo-sized duodenoscope (5.5-mm channel) was previously available as a “mother/baby” scope system to allow passage of a cholangioscope (see Chapter 27 ). However, this system was difficult to manipulate and is now rarely used.

Forward-Viewing Endoscopes

Upper endoscopes, colonoscopes, and enteroscopes are used in patients with surgically altered anatomy (e.g., hepaticojejunostomy, gastrectomy with Roux-en-Y anatomy) (see Chapter 31 ). Conventional forward-viewing endoscopes do not have an elevator and are limited with respect to control of accessories during cannulation or therapy. In addition, visualization of the ampulla may be limited. When using a colonoscope, “long” length accessories may be needed, as not all standard biliary accessories are of adequate length.

Balloon-Assisted Enteroscopes

Single-balloon (Olympus America Inc., Lehigh Valley, PA) and double-balloon (Fujinon, Tokyo, Japan) enteroscopes enable deep intubation of the small bowel. These endoscopes have a specialized disposable overtube with an inflatable balloon that anchors the endoscope in place during shortening maneuvers. Double-balloon enteroscopes have a second balloon on the endoscope insertion tube. Balloon-assisted enteroscopes enable diagnostic and therapeutic ERCP in most patients with surgically altered anatomy. However, there are few available accessories for therapeutic interventions because these enteroscopes have long lengths (200 cm) and small-diameter working channels. A “short” double-balloon enteroscope (Fujinon, Tokyo, Japan) with a 2.8-mm working channel and a 152-cm working length allows standard biliary accessories of ≤7-Fr diameter to be used. More recently, this same endoscope has become available with a 3.2-mm working channel. However, the combination of a forward view and the lack of an elevator limits the success rate in patients with intact papilla for enteroscopy-assisted procedures. Recently the American Society for Gastrointestinal Endoscopy (ASGE) published a detailed report on devices and techniques used for ERCP in the surgically altered gastrointestinal (GI) tract.

Echoendoscopes

Curvilinear echoendoscopes (GF-UC180 or GF-UCT180; Olympus America Inc., Lehigh Valley, PA, and Pentax, Montvale, NJ) have been used successfully to obtain access to biliary or pancreatic ducts in patients with failed ERCP and those with inaccessible papillae (see Chapters 32 and 33 ). Therapeutic curvilinear echoendoscopes (Pentax and Olympus America Inc.) with 3.8-mm working channel allow passage of standard ERCP accessories for transmural access and drainage of pancreatic fluid collections with ability to place large-diameter (10 Fr) plastic stents or self-expandable metal stents that have large-diameter delivery systems. A 19-gauge or 22-gauge fine-needle aspiration needle or cautery device (Cystotome [Cook Endoscopy, Winston-Salem, NC], standard needle knife) can be used for puncture and entry at the defined location under real-time ultrasound guidance (see Chapter 56 ). The Cystotome ( Fig. 4.2 ) is an electrocautery system that incorporates an inner wire with a large-diameter needle-knife tip on a 5-Fr inner catheter, and a 10-Fr outer catheter equipped with a diathermy ring at its distal tip. The proximal end of this device includes a handle with connectors for active cords for each of the two cautery components and a fitting to provide for injection of contrast. The Cystotome is discussed in more detail in Chapter 32 . Recently, fully covered lumen-apposing self-expanding metal stents (LAMS) ( Fig. 4.3 ) have been introduced and appear to be safe and effective for draining a variety of pancreatic fluid collections (see Chapter 56 ), such as pancreatic pseudocysts and walled-off pancreatic necrosis. Advantages of LAMS over other stents include single-step deployment, short length, large diameter, and ability to perform direct endoscopic necrosectomy while limiting stent migration.

Standard Cannulation Catheters

Standard ERCP cannulas are 5-Fr to 7-Fr catheters, with straight, tapered, or rounded tips that accept guidewires up to 0.035-inch diameters ( Fig. 4.4, A ). Use of double-lumen or triple-lumen devices or attachment of a side-arm adaptor allows contrast injection without need for removal of the guidewire. The use of tapered-tip (4.5 Fr to 4 Fr to 3.5 Fr) or ultratapered-tip (5 Fr to 4 Fr to 3 Fr) catheters may improve ductal access. However, these tapered-tip cannulas often accommodate only smaller-caliber guidewires (0.018 to 0.025 inches). There are no published studies that directly compare cannulation success rates between standard and tapered catheters, and the latter carry a higher risk of submucosal injection.

Standard cannulas with or without guidewires are limited in their ability to vary the angle of approach to the papilla. The swing-tip catheter (Olympus America Inc.) ( Fig. 4.4, B ) overcomes the limitations of conventional catheters and offers the endoscopist the ability to bend the cannula tip in either the up–down or left–right directions, thereby facilitating biliary cannulation or selective entry into the right or left hepatic ducts.

The Cremer needle-tip catheter (Cook Endoscopy) is 1.8 mm in diameter and has a metal needle tip that facilitates minor papilla cannulation ( Fig. 4.5, A and B ).

The standard pancreaticobiliary manometry catheter is a water-perfused 5-Fr catheter with a tip diameter of 3.5 Fr and is used during sphincter of Oddi manometry studies ( Fig. 4.6, A ) (see Chapter 16 ). A variety of catheter types can also be used. Some manometry catheters have a longer “nose” to help maintain catheter position. The standard catheter has three side ports spaced 2 mm apart for simultaneous pressure measurement. The Lehman manometry catheter (Cook Endoscopy) sacrifices one port for aspiration of water from the pancreatic duct during infusion to prevent overfilling; this reduces the risk of post-ERCP pancreatitis (PEP). Standard water-perfused motility recording systems used for esophageal manometry are utilized for sphincter of Oddi manometry. More recently, a compact water perfusion pump has become available (Mui Scientific, Mississauga, Canada) ( Fig. 4.6, B ). A microtransducer catheter that does not require water perfusion is also available. This catheter appears to be associated with a lower risk of PEP. A detailed discussion on currently available sphincter of Oddi manometry devices can be found in technology status evaluation report by the ASGE and in Chapter 16 .

Sphincterotomes

Pull-type (Erlangen) sphincterotomes were designed for biliary sphincterotomy. They consist of a Teflon catheter containing a continuous wire loop with 20 to 30 mm of exposed wire exiting at a variable distance from the tip ( Fig. 4.7, A ). Early precut sphincterotomes were pull type, and the cutting wire extended to the tip ( Fig. 4.7, A ). The other end of the wire is insulated and connected to an electrosurgical unit. Over the last decade or so, endoscopists have recognized the need to angle the catheter upward to selectively enter the bile duct. Subsequently, prospective randomized trials comparing standard catheters with sphincterotomes have shown a cannulation rate of 84% to 97% with sphincterotomes compared with 62% to 67% with standard catheters (see Chapter 17 ). In addition, because sphincterotomy is performed in a large percentage of ERCPs, sphincterotomes have become the primary biliary cannulation device during ERCP in patients with native anatomy and an intact papilla.

Sphincterotomes are available with single, double, and triple lumens; nearly all units have moved to the use of triple-lumen devices. Double-lumen sphincterotomes allow for either injection of contrast or introduction of a guidewire and facilitate cannulation and therapeutic interventions. Contrast can be injected either by removing the guidewire or by leaving the wire in and using a side arm adaptor (e.g., Tuohy-Borst Adapter; Cook Medical). Triple-lumen sphincterotomes allow injection of contrast without the need for removing the wire because there is an additional port. Unfortunately, because of the small size of the injection lumen, the contrast infuses slowly and with much resistance, making it difficult for the assistant because of the force required during injection. Contrast injection is facilitated by the use of a small syringe and by dilution of contrast, as full-strength contrast is more viscous. A sphincterotome is available that incorporates a combination of cutting and balloon stone extraction (Stonetome; Boston Scientific, Marlborough, MA); however, the addition of a balloon increases the catheter diameter and tip size, which may make cannulation more difficult.

When sphincterotomy is performed, a variety of generator currents can be used: cutting, autocut, coagulation, or blended. Limited data suggest that the use of a pure cutting current is associated with a lower risk of PEP, whereas the use of an autocut mode is associated with a lower risk of intraprocedural bleeding and eliminated the “zipper cut” phenomenon during sphincterotomy. When performing pancreatic sphincterotomy, pure cutting current is often used to reduce the risk of pancreatic duct injury and subsequent stenosis (see Chapter 11 ).

Rotatable sphincterotomes are designed to rotate the tip so that one can alter the desired trajectory of cannulation, which may be useful in improving cannulation, especially in patients with unusually oriented or distorted papillae or in patients with Billroth II–type anatomy. Rotatable sphincterotomes may also help orient the cutting wire during sphincterotomy. However, no published data are available to show this advantage. A wire-guided sphincterotome with a cutting wire oriented in the opposite direction relative to standard sphincterotome is available for use in Billroth II–type anatomy (Cook Endoscopy). In addition, a sphincterotome with an S-shaped tip is also useful in patients with surgically altered anatomy.

Guidewires are used with a standard catheter or sphincterotome to achieve deep cannulation of the bile and pancreatic ducts. Wire-guided cannulation is associated with increased cannulation success rates and a lower risk of PEP. A randomized controlled trial found no difference in cannulation success and adverse event rates between 5-Fr and 4-Fr sphincterotomes. For further information on biliary cannulation, see Chapter 14 .

Access Sphincterotomes

Precut or “access” sphincterotomy refers to a variety of endoscopic techniques used to gain access to the bile or pancreatic duct after conventional methods of cannulation have failed (see Chapter 15 ). Needle-knife and precut sphincterotomes are the two most commonly used devices to gain access into the bile duct. The needle-knife sphincterotome was first described by Huibregtse in 1981 and is essentially a bare electrocautery wire that protrudes 4 to 5 mm from the end of a Teflon catheter ( Fig. 4.7, B ). Several publications discuss the use of this device. Additional versions include additional lumens for guidewire passage or contrast injection (double lumen) and both wire and contrast injection (triple lumen). The precut sphincterotome was first reported by Soehendra and the Hamburg group in 1996 ( Fig. 4.7, A ). This sphincterotome allows “papillary roof incision.” A double-lumen version is also available. It has the advantage of having separate lumens for contrast and guidewire. Biliary sphincterotomy can be immediately completed by using the same instrument and is facilitated by having a preloaded hydrophilic-tip wire. A new needle-knife sphincterotome has an insulated tip to prevent energy dispersion from the tip of the incising needle. The coated-tip needle knife is believed to prevent unintentional deep cuts or perforations because it enables users to keep the sphincterotome tight in the papillary orifice. The optimal device for precut sphincterotomy is unknown because there are limited data comparing different precut techniques and devices.

Guidewires

Guidewires are the cornerstone of diagnostic and therapeutic ERCP. During ERCP, guidewires are used for cannulation and for achieving and maintaining access and placing and exchanging devices. Guidewires are useful for cannulation, essential for passage of accessories, and useful to guide sphincterotomy, and are required for traversing strictures, stricture dilation, cytologic tissue sampling, and stent placement.

Ideal guidewire characteristics for gaining access to the duct of interest and traversing stricture are different from those for advancement and exchange of accessories. Guidewires with slippery and flexible leading tips and shafts are generally used for cannulation and to gain access through tight biliary and pancreatic strictures, but may be difficult to keep in place during exchange. On the other hand, stiff and taut guidewires are best used for advancement of devices such as biliary stents or dilators. Stiff and taut wires also minimize lateral deviation and facilitate forward axial transmission of forces. Friction can aid in maintaining wire tension but hinders both wire and device movement. A variety of guidewires are currently available ( Table 4.1 ) and these vary in material, length, diameter, and design to optimize performance.

In general, three guidewire designs are available for ERCP applications: (1) Monofilament wires are designed for rigidity and made of stainless steel. (2) Coiled wires are stiff and flexible and have an inner monofilament core and an outer spiral coil made of stainless steel. Inner core and outer spiral coil design provide stiffness and flexibility, respectively. Most coiled wires are coated with Teflon (DuPont, Washington, DE) to minimize resistance and to optimize traversing tortuous biliary strictures because of combined stiffness and flexibility. (3) Coated or sheathed wires have a monofilament core made of stainless steel or nitinol and an outer sheath made of Teflon, polyurethane, or another lubricious polymer. The outer sheath material improves radiopacity, slipperiness, and electrical insulation properties. Flexibility of coated wire tips depends on the taper of the inner core. Many wires have a platinum-tipped core to improve fluoroscopic visualization. The configuration of the guidewire can be straight or angled (J-shaped) ( Fig. 4.8, A ). Some wires have graduated or continuous markings for visual endoscopic measurement or movement detection. Most wires are only minimally steerable in the radial direction.

Guidewires are advanced under fluoroscopic monitoring through a catheter or sphincterotome, which imparts stiffness and direction. Guidewire passage is easier after flushing water through dry or contrast-filled devices by minimizing friction, because contrast is “sticky.” Moistening hydrophilic portions of a guidewire prevents drying and sticking of the wire to the accessories. Maintenance of wire position is critical for safe and effective use of over-the-wire accessories, such as dilators and stents. The risk of wire displacement can be minimized by using guidewires that have graduated or continuous markings or movement detection, printed distance markers, and movement guides ( Fig. 4.8, B ). In addition, fixation of the proximal end (outside the patient) using short-wire system locking devices can also decrease the risk of wire dislodgement.

Guidewire types include conventional, hydrophilic, and “hybrid,” with diameters ranging from 0.018 to 0.035 inches and lengths most often ranging from 260 to 480 cm, and are summarized in Table 4.1 . Wire lengths longer than 400 cm (up to 600 cm) are used for “long-length” exchange of longer accessories used with 200-cm endoscopes during altered anatomy ERCP. It is recommended that coated wires approved for use during electrocautery applications are used during sphincterotomy.

Data are limited regarding the relative efficacy of specific wires for ERCP applications. Clinical experience suggests that coated and hydrophilic wires improve ERCP success rates in negotiating difficult papillae or strictures. Completely hydrophilic wires (Glidewire; Olympus Corporation, and Terumo, Tokyo, Japan) are slippery and highly torqueable, allowing difficult strictures to be traversed, but can make catheter exchange difficult, leading to inadvertent displacement from ducts or strictures. Combination (hybrid) wires—such as Jagwire, Hydra Jagwire (Boston Scientific); FX, X (ConMed, Utica, NY); VisiGlide (Olympus America Inc.); and Metro (Cook Endoscopy)—provide a combination of a slippery tip with a nonslippery, stiffer shaft ( Fig. 4.8, A ). As mentioned earlier, recent data suggest that biliary cannulation using a guidewire through a sphincterotome lowers the risk of PEP, presumably because of less trauma to the papilla and limited pancreatic injection. Teflon-coated wires are least expensive, but rarely used. Hybrid wires are more user-friendly but more expensive. A useful and detailed review of guidewires can be found in a recent ASGE technology assessment report.