Biliary stents, why, when and who?

  1. Gastroepato
  2. Gastroenterology
  3. Biliary stents, why, when and who?
  4. Sphincterotomy endoscopy
  5. Dysfunction of the sphincter of Oddi

Why a stent of the biliary tract? Which role?

 It is indicated in the case in which it is necessary to restore the drainage of the same biliary way: classic example is the tumor of the head of the pancreas which compresses ab extrinsic, ie from outside, the course of the intrapancreatic choledochus and determines an obstacle to the outflow of the bile, with consequent neoplastic obstructive jaundice. Before the advent of the bile stents, which are positioned during a complex endoscopic procedure called "ERCP" or pancreatographiographed endoscopy, using a guide wire on which to slide the stents. This procedure uses a thrust tube, which allows to position the drainage at the ideal point. In the past, many years ago, the only treatment available was the surgical procedures of biliodigestive by-pass. The first non-surgical treatment was percutaneous transhepatic drainage and later the insertion of prostheses percutaneously

Obstruction of the biliary tract, however, is a very common condition and can be caused by:

a) from benign diseases affecting the biliary tract (eg biliary calculi)
b) tumors that compress or invade the bile ducts (eg pancreatic cancer, cholangiocarcinoma, ampullomas, etc.)

The resulting obstructive jaundice requires treatment in order to reduce pruritus, nausea and lack of appetite. These methods have never achieved great popularity due to complications that severely affect the quality of life of patients. Endoscopic biliary drainage methods have been developed since 1979.

Contraindications for biliary stents

The contraindications depend on the nature of biliary strictures. Malignant stenosis should always be treated and there is virtually no contraindication for this category of patients. Coagulation disorders pose a relative contraindication only in those patients requiring sphincterotomy prior to placement of the prosthesis. The use of prostheses in benign biliary strictures and pancreatic ducts is still under discussion. Metallic stents can not be removed, so their use should be restricted to unresectable malignant stenosis.Protesi in plastica della via biliare da posizionare con ERCP

Indications for the biliary stent

Palliation of the malignant obstructions of the biliary tract caused by ampullary carcinoma, pancreatic cancer, biliary tract carcinoma and metastatic disease can be achieved by the insertion of bile prostheses. This procedure can be used to improve the patient's clinical condition before major surgery, or it may represent the definitive palliative treatment. Other indications are obstructive jaundice from chronic pancreatitis, surgical trauma or primary sclerosing cholangitis. A bile prosthesis can also be used as a temporary measure in patients with biliary tract calculations that can not be removed after sphincterotomy to prevent the development of a cholangitis.

Endoscopes

Biliary therapeutic procedures are best performed with wide-channel side endoscopes (4.2 or 4.5 mm). Some endoscopists still prefer to perform perendoscopic retrograde cholangiography (ERCP) and sphincterotomy with a small-caliber lateral vision endoscope or with an instrumental canal with a diameter of 2.7 mm or 3-2 mm.

StentsERCP: vie biliare principale dilatata enormemente, stenosi del tratto distale del coledoco

The most commonly used biliary stents are the rectilinear type, provided with terminal wings to lock them in place and prevent their displacement. These stents are made of polyethylene, polyurethane or teflon and are commercially available in diameters of 7,8,10 and 11.5 Fr and length of 5,9,11,14 or 19 cm. The double-pig prostheses are still used in special situations such as biliary lithiasis and drainage of pancreatic pseudocysts.

Expandable stent with balloon or self-expanding metal typeProtesi di Wall-stent

The main problem with plastic stents is the occlusion of biliary sand. Therefore numerous attempts have been made to develop from a larger diameter stent. Two types of stents are available today: self-expanding metal implants (Wallstent, Schneider, Gianturco, Wilson-Cook Medical) and expanding foam implants (Strecker, Microvasive, Palmaz, Johnson & Johnson). Wallstents are made of filamentary material organized to form a tubular structure. They are foldable, self-expandable and flexible along the longitudinal axis. Their diameter is substantially reduced by elongation. The positioning system includes a 9 Fr coaxial catheter with an invaginated membrane enclosing the prosthesis. The coaxial catheter friction is reduced when the invaginated membrane is filled with a contrast medium diluted at a pressure of 5.0 atm. The stent can then be slowly released by withdrawing the outer membrane. The prosthesis itself is radiopaque. Additional radiopaque markers are present on the catheter and allow accurate placement of the prosthesis. The length is 10 cm and a diameter of + 3 mm or 9 Fr in the unexpanded shape and 6.8 cm and 8-10 mm or + 30 Fr in the expanded form. The stent is placed on a 4 mm guide catheter.

Catheters


The large-caliber plastic stents are inserted on a guiding catheter. In principle, two types of catheter were available: one equipped with a metal hook at the level of the terminal portion for fluoroscopy viewing, the other with a rounded tip with two metal rings 7 cm apart for measuring the distance between stenosis and papilla, which allow to evaluate the length of the prosthesis. The external diameter of the catheter-guide is essential. The catheter should enter exactly inside the prosthesis. The prosthesis can then be introduced above the guiding catheter with less resistance to the stenosis site.

Catheter-guide

New guide catheters have been developed in recent years. Teflon-coated stainless steel lead catheters with or without a core have different lengths (260,400,480 cm) and diameter variability (0.018, 0.025.0.035.0.038 inches, 0.046, 0.063.0.089, 0.096 cm). The flexible tip of the guide wire is atraumatic. The length of the flexible tip can be varied by a maneuver of the inner core, advancing it or withdrawing it inside the guide wire. These guide wires are not twistable and can be easily blocked and are still mainly used to change catheters or spheres.

 

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Link correlati al tema svolto: calcolosi della via biliare
cancro del pancreas
ampullomi
ittero neoplastico