Endoscope Requirements

Nearly all modern duodenoscopes have a therapeutic channel of 4.2 mm that can accommodate stents up to 11.5 Fr in diameter. However, smaller diameter working channels such as in balloon enteroscopes and pediatric colonoscopes only permit placement of 7 Fr diameter stents.

Distal Biliary Obstruction

The approach to distal biliary strictures is more straightforward than for hilar tumors and will be discussed separately. After successful deep cannulation of the biliary tree contrast is introduced to clearly elucidate the margins of the stricture to allow for selection of the appropriate stent length. The stricture is traversed with a guidewire. It is important to pass the wire well proximal to the stricture to prevent wire loss and to provide mechanical advantage, although care must be taken to preclude perforation through the liver capsule. In general, a biliary sphincterotomy is not required for insertion of stents up to 10 Fr diameter¹⁰ and is not protective of post-ERCP pancreatitis after stent placement for malignant biliary obstruction.¹¹ However, one study showed that in patients with bile leaks, placement of 10 Fr stents without a sphincterotomy was associated with a higher rate of post-ERCP pancreatitis.¹² A biliary sphincterotomy is required when multiple stents are placed, such as in the treatment of benign strictures (see Chapter 40).¹⁰

When placing a single 10 Fr stent, it is rarely necessary to dilate the stricture, since the mechanical advantage is great enough to overcome resistance. In cases of uncertainty, a 10 Fr dilating catheter (e.g., Soehendra dilator, Cook Endoscopy, Winston-Salem, N.C.) can be passed and if it easily traverses the stricture, balloon dilation is not required. Otherwise, hydrostatic balloon dilation can be performed. When the insertion of multiple stents is planned, stricture dilation is essential. In this setting, more than one guidewire may be placed prior to insertion of the first stent. Alternatively, a guidewire can be placed after each stent insertion by recannulating the bile duct alongside the stents. A useful tip in placing more than one wire is to pass a large or multilumen catheter over the initial guidewire. This can be accomplished with a triple-lumen cytology brush sheath. More recently, an “intraductal exchange” can be performed using the Fusion system (Cook Endoscopy) and the short-wire lumen. During each stent placement the wire can be separated from the delivery system to allow additional stents to be placed sequentially using a single guidewire.

When multiple stents are placed, using a slightly longer initial stent is helpful as the friction created by passage of additional stents during insertion may result in upward movement. If the first stent is too short, it may migrate into the duct. This is usually of no consequence assuming that the stent is still across the stricture. The length of the stent chosen is based on the distance from the papilla to the proximal edge of the stricture plus an additional 2 cm. Excessively long stents should be avoided, as distal migration tends to occur into the duodenum until the proximal flange or pigtail impacts at the top of the stricture; meanwhile, the distal end of the stent may impact and perforate the opposite duodenal wall (Fig. 21.8). In general, 5- or 7-cm–long stents are of sufficient length for nearly all biliary strictures resulting from pancreatic cancer. Defining the stricture length can be achieved in several ways. One way is during withdrawal of the initial cannulating catheter. When the catheter tip is at the proximal end of the stricture, the endoscopist holds the catheter just outside the biopsy port; the catheter is withdrawn until it is endoscopically visible in the duodenum just distal to the papilla. The distance from the endoscopist’s fingers to the biopsy port is measured and represents the stricture length. Anecdotally, this method seems to overestimate the length of the stricture. Another way is to use the radiograph to measure the length of the stricture. When the tip of the endoscope is in contact with the papilla, a radiographic image is captured. The distance from the tip of the endoscope to the proximal edge of the stricture is measured. The diameter of the endoscope is used as a comparison measuring point to determine the true stricture length and account for a magnification factor. The following equation is used to solve for the unknown variable X, which is true stricture length (Fig. 21.9):

Fig. 21.8 Endoscopic photos of a distally migrated 11.5 Fr biliary stent impacted against the duodenal wall opposite the major papilla. A, Before removal and B, after removal, a small defect is seen.

Fig. 21.9 Measurement on the radiograph to calculate stent length. A, The measurement from the top of the stricture to endoscope tip when positioned at the papilla (bracket) compared to the diameter of the endoscope (arrowheads) was 7:1. B, Since the diameter of the endoscope was 11.5 mm, a 9-cm stent was placed.

Finally, fluoroscopic markers separated by a known distance are available on some catheters and guidewires and can be used as a reference point to the stricture and papilla. Balloon dilation catheters also have radiopaque markers corresponding to the length of the balloon.

Once the stent has been selected, placement is undertaken. If a taper is present, it represents the proximal end. Depending on the type of stent system, either the inner guiding catheter alone or the inner guiding catheter and stent are advanced over the guidewire. It is important that the wire does not pass too far proximally into the biliary tree during advancement, since this could cause injury to the intrahepatic ducts or liver capsule. Conversely, excessive traction on the wire may result in wire loss. The stent is then advanced over the guide catheter by advancing the pusher tube. The latter has a larger bore that approximates the diameter of the stent. During advancement, the elevator should remain closed. When the stent impacts the elevator, the elevator is opened slightly to allow it to emerge from the endoscope channel. The elevator is closed to direct the stent upward and into the papilla. It is imperative to maintain a short endoscope position with the tip as close as possible to the papilla to maintain maximal mechanical advantage. Using a series of small movements in which the elevator is sequentially lowered to allow advancement of the stent and then closed to advance the stent in a “ratchet-like” manner, the stent is advanced into the bile duct. Upward tip deflection as well as withdrawing the endoscope shaft further shortens the scope and provides forward motion to the stent. It is important to note that allowing more than a minimal amount of stent to be advanced out of the endoscope into the duodenum decreases the mechanical advantage to forward advancement due to looping and buckling. To facilitate forward movement of the stent, the endoscopy assistant must provide traction on the inner guiding catheter (or guidewire if there is no inner guiding catheter). Once optimal stent position is achieved, the inner guiding catheter and guidewire are removed while the endoscopist maintains forward pressure with the pusher tube against the stent to prevent distal stent dislodgement. If additional contrast is needed to assess drainage or intrahepatic anatomy above the stent, the guidewire can be removed prior to removing the inner guiding catheter to allow contrast injection (this is only possible when long wire systems are used). The process is repeated for additional stent placement.

In patients with short, distal bile strictures (e.g., chronic pancreatitis, postsphincterotomy ampullary stricture), three to four 10 Fr 5-cm–long stents can be mounted on the inner guiding catheter at one time. Once the first stent is placed (Fig. 21.10) the inner guiding catheter and guidewire are withdrawn just enough to release this first stent; the duct is then recannulated alongside the first stent with the second stent, guidewire, and inner guiding catheter. The process is continued until all stents are deployed. Alternatively, the stents can be placed one by one alongside each stent (Fig. 21.11).

Fig. 21.10 Insertion of multiple 10 Fr stents. A, The first stent (1) is being pushed by the second stent (2) since the actual pusher tube is still well above the multiple stents loaded onto the catheter. B, Final result of four 10 Fr stents, all placed with one passage of the stent introducer system.

Related posts:

Endoscopic Ultrasound–Assisted Access to the Pancreatic Duct The ERCP Room Cholangioscopy Access (Precut) Papillotomy Biliary Surgery Adverse Events Including Liver Transplantation ERCP for Acute and Chronic Adverse Events of Pancreatic Surgery and Pancreatic Trauma

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