Biliary stents, why, when and who?
- Gastroepato
- Gastroenterology
- Biliary stents, why, when and who?
- Sphincterotomy endoscopy
- 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.
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.
Stents
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 type
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.
> Protesi biliari
Hepatology index
Link correlati al tema svolto:
calcolosi della via biliare
cancro del pancreas
ampullomi
ittero neoplastico