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634 Current Designs of Self-Expanding Stents
Fig. 4.18 Self-expanding plastic stent (Poly fl ex) with
capture basket for loading into the delivery system
( arrowheads )
Bowel
Enteral stents are traditionally placed without
covering membrane as the migration rate of covered stents is very high. The risk of displacement
in the colon is increased by the passage of feces.
It is important that constipation is avoided, but
there is no consensus whether a low-residue diet
or a diet high in soluble fi ber is preferable. From
a practical point of view, anything that keeps the
patient regular must be a good thing, and stoolsoftening laxatives should be given routinely.
Unfortunately, uncovered stents migrate less but
occlude in almost 25%. Compound knitted stents,
which sandwich a membrane between two layers
of wire mesh, should be a good compromise, but
initial outcome data are equivocal [
15, 38 ] . The
poor performance of laser-cut enteral stents however con fi rms that fl exibility and conformability
are a priority for enteral stents.
Bile Duct
Fig. 4.19 Esophageal stent with antimigration collar
(Ella-HV+)
Antire fl ux Stents
Stents placed with their lower end in the gastric
fundus predispose the patient to re fl ux of gastric
content. The fundus is the lowest part of the
stomach in the supine position, and hydrostatic
pressure will force gastric content through a stent
into the mid and upper esophagus. This is readily
demonstrated on CT scanning. Most esophageal
stents are available with an antire fl ux valve
(Fig. 4.22 ), but the clinical bene fi t of a valve is
still controversial [ 31 ] . However, limited evi-
dence suggests potential for a signi fi cant bene fi t,
including reduced need for antire fl ux medication
and prevention of aspiration pneumonia and fatal
aspiration [
life [
Galway, Ireland) may be inserted into patients
with an open stent who have troublesome regurgitation of gastric content (Fig. 4.23 ) [ 37 ] .
5, 32– 35 ] and increased quality of
36 ] . A stand-alone retro fi t valve (Vysera,
The greatest variety of different designs are seen
in biliary stents, including membrane-based
stents and numerous laser-cut stents as spin-offs
from vascular designs (Fig. 4.24 ). Due to the
nature of their tubular design, alignment of lasercut stents is inferior to woven stents (Fig. 4.25 ),
and fractures are not uncommon. Stent occlusion
requiring reintervention is increasingly required
due to extended patient survival from improved
chemotherapy regimes. This becomes particularly challenging if the existing stent does not
conform to the biliary anatomy, and reintervention is only possible through the side of the stent
skeleton (Fig.
4.26 ). Care must be taken not to
become entangled in the sharp edges of a lasercut stent.
Covered stents are available for the biliary
tree, but these should be considered with great
caution. There is a high risk of irreversibly
occluding biliary side branches: the cystic duct or
the pancreatic duct. In case of a pancreatic head
cancer, a covered stent may be a good choice if
this can be placed below the origin of the cystic
duct. However, obstruction of this can lead to
64
Fig. 4.20 Esophageal stent with uncovered antimigration segment for mucosal ingrowth (Niti-S double)
H.-U. Laasch
Fig. 4.21 Migrated esophageal stent (Boubella) at ileocecal junction
Fig. 4.23 Antire fl ux valve for retro fi tting into an open
stent. The silicone valve is mounted in a segment of uncovered nitinol stent, which requires loading into a standard
esophageal stent delivery system (viewed from below)
Fig. 4.22 Stents with antire fl ux valves. ( a ) Dua (Cook);
( b ) Hanaro (MI-Tech); ( c ) Niti-S double (Taewoong);
( d ) Ella-HV (Ella-CS)
increasing dilatation of the gallbladder and cholecystitis. The indiscriminate use of covered stents
may result in unsalvageable occlusion of essential segmental ducts (Fig. 4.27 ).
Tumors of the biliary hilum represent a particular challenge. Skilled endoscopists will be able to
place bilateral plastic stents in most cases, but these
will occlude within 6–12 months. Larger-diameter
654 Current Designs of Self-Expanding Stents
Fig. 4.24 Biliary stents. ( a ) Ella-SX (braided); ( b )
Covered Wallstent (braided); ( c ) Luminexx (laser-cut);
( d ) PTFE membrane-based Viabil stent with nitinol struts
Fig. 4.25 Luminal patency within a tight bend is well
maintained in a knitted ( a ) and braided stent ( b ), whereas
the laser-cut stent ( c ) kinks
metal stents tend to give a better long-term result,
but bilateral placement is dif fi cult endoscopically
[ 39 ] . To allow stenting of both hepatic ducts through
a single percutaneous approach, fenestrated stents
are available, which allow initial placement from
one hepatic duct to the other [ 40 ] , with a further
stent inserted downstream through the window,
resulting in a coaxial T-con fi guration (Fig. 4.28 ).
An uncovered stent must be used for this; otherwise, the contralateral side is excluded.
(WL Gore, Flagstaff, AZ, USA); ( e ) T-stent for hilar stric-
tures (Niti-S); ( f ) Bare and covered Egis (knitted)
Biodegradable biliary stents are not routinely available, but custom-made devices have
been used successfully for treatment of
in fl ammatory biliary strictures [ 22 ] . They may
play an important role in the future with the
increasing numbers of liver transplantations
and radical pancreaticoduodenectomies. At
present, they are only available off-label with
large delivery sheaths up to 13 French, which
require very large transhepatic tracks and
negate endoscopic insertion.
Delivery Systems
Designs for delivery systems have converged
onto pullback systems, where the stent is
released by withdrawing the constraining
sheath. The only remaining exception is the
Ultra fl ex system (Boston Scienti fi c) where the
stent is tied down to the delivery system with
loops of silk thread (Fig. 4.29 ). This unravels
on traction like grandmother’s jumper. The disadvantage is the large size and the very rough
outer pro fi le of the system, which frequently
necessitates predilatation of the stricture in
66
H.-U. Laasch
Fig. 4.26 Reintervention for occluded laser-cut stent
(pancreatic carcinoma) ( a ) Coronal CT reconstruction
shows a poorly aligned, blocked stent (Luminexx) in a
dilated bile duct ( arrowheads ). The upper end is partially
embedded in the roof of the bile duct ( arrow ). An enteral
Wall fl ex stent is present in the duodenum. ( b ) Attempts at
Fig. 4.27 Occlusion of segmental ducts by placement of
bilateral covered biliary stents. Percutaneous cholangiography shows holdup of contrast medium at the junction
with the covered stent ( arrow ) (Courtesy of Dr. E. Bakir,
North Manchester General Hospital, UK)
cannulation of the stent failed, and the second stent
(Niti-S) could only be placed through the side ( arrow ) of
the fi rst stent. The angulation of the laser-cut stent ( arrow-
head ) indicates partial fracture. This became separated on
follow-up CT (Courtesy of Dr. E. Bakir, North Manchester
General Hospital, UK)
order to pass the stent. Pullback delivery systems
for most metal esophageal stents measure
16–18 Fr (5–6 mm diameter) but can be considerably larger (e.g., Poly fl ex). A radiopaque ring
at the end of the sheath reduces uncertainty about
the degree of deployment. For resheathable
stents, a marker indicating the point of no return
is helpful. Increased control over the deployment
process is offered by a pistol grip, where repeated
pulling of the trigger slowly withdraws the
sheath (Evolution, Cook); the process can be
reversed to resheath the stent. It is available for
esophageal, enteral, and biliary stents.
The tip of a large delivery system may impact
in the deployed stent on withdrawal if the stent
has not suf fi ciently expanded. A quirky delivery
system for the early Ella-CS stents consisted of
an angioplasty catheter, where the balloon formed
the introducer tip. This was de fl ated prior to
deployment, and impaction was completely
avoided. It has now been replaced by a tip that
sheds two parts of a plastic dilatation on release
of the stent (Fig. 4.30 ). An interim design with a
longer releasable tip was abandoned following a
case of a perforated sigmoid diverticulum caused
by impaction of the tip.
Fig. 4.28 ( a – c ) Single puncture approach to hilar tumors affecting both hepatic ducts. A fenestrated knitted T-stent is
placed from right to left , followed by a woven stent through the window into the common duct (Both Niti-S)
674 Current Designs of Self-Expanding Stents
Fig. 4.29 Thread-release delivery system (Ultra fl ex precision). ( a ) Undeployed; ( b ) Part-deployed colonic stent
The DIY experience of loading the Poly fl ex
system can be a challenge to the less playful
operator. More importantly though, a balanced
choice has to be made between the cost-savings
of the stent against the large size and rigidity of
the delivery system.
Some esophageal stents are available on a
proximal release system for high strictures close
to the upper esophageal sphincter (Fig. 4.31 ).
Foreign body sensation increases above the
upper margin of C7 vertebral body, and accurate
Fig. 4.30 Compound tip of Ella delivery system. Two
plastic dilator cones automatically detach from the fl exible
central tip on deployment. Note the metal marker ring on
the distal end of the delivery sheath ( arrow )
positioning of the proximal end of the stent is
essential in the cervical esophagus. The whole
sheath is advanced distally and requires removal
though the released stent. This requires suf fi cient
68
H.-U. Laasch
Fig. 4.31 Proximal release system (Ella-HV). The delivery sheath pushes forward, releasing the stent from the
top . It is removed through the deployed stent
length of guide wire below the stricture and
adequate stent expansion for removal of the system through it.
Few differences between delivery systems for
biliary and enteral stents exist; they are mainly
limited to the presence of radiopaque markers
and nitinol reinforcement of the constraining
sheath.
Summary
An understanding of the properties of different
stent designs is helpful in choosing the most
appropriate stent for each situation, but departments can only stock a limited supply. Better
collaboration between scientists, industry, and
clinicians is needed to change current trial-anderror development to purposeful optimization of
designs. Ideally, this would involve mathematical
modeling as well as a better understanding of
stent behavior within the human body.
Acknowledgments The author would like to thank
BVM Medical, COOK UK, Ella-CS, and UK Medical for
their support with demonstration models and S&G
Biotech for the provision of images from the manufacturing process.
References
1. Robertson SW, Ritchie RO. In vitro fatigue-crack
growth and fracture toughness behavior of thin-walled
superelastic nitinol tube for endovascular stents: a
basis for de fi ning the effect of crack-like defects.
Biomaterials. 2007;28:700–9.
2. Hajdinjak T, Patel M, Papatsoris A, Masood J,
Buchholz N, Birch M. In vitro simulation of stent
fracture mechanisms in ureteric nitinol wire stents.
Urol Res. 2008;36:241–5.
3. Nikanorov A, Smouse HB, Osman K, Bialas M,
Shrivastava S, Schwartz LB. Fracture of self-expanding
nitinol stents stressed in vitro under simulated intravascular conditions. J Vasc Surg. 2008;48:435–40.
4. Kauffman GB, Mayo I. The story of nitinol: the serendipitous discovery of the memory metal and its applications. Chem Educ. 1996;2:1–21.
5. Laasch HU, Marriott A, Wilbraham L, Tunnah S,
England RE, Martin DF. Effectiveness of open versus antire fl ux stents for palliation of distal esophageal carcinoma and prevention of symptomatic
gastroesophageal re fl ux. Radiology. 2002;225:
359–65.
6. Peck R, Wattam J. Fracture of Memotherm metallic
stents in the biliary tract. Cardiovasc Intervent Radiol.
2000;23:55–6.
7. Odurny A. Colonic anastomotic stenoses and
Memotherm stent fracture: a report of three cases.
Cardiovasc Intervent Radiol. 2001;24:336–9.
8. Suzuki N, Saunders BP, Thomas-Gibson S, Marshall
M, Halligan S, Northover JM. Complications of
colonic stenting: a case of stent migration and fracture. Endoscopy. 2003;35:1085.
9. Stern N, Smart H. Repeated enteral stent fracture in
patient with benign duodenal stricture. Gastrointest
Endosc. 2010;72:655–7.
10. Piesman M, Kozarek RA, Brandabur JJ, et al. Improved
oral intake after palliative duodenal stenting for malignant obstruction: a prospective multicenter clinical
trial. Am J Gastroenterol. 2009;104:2404–11.
11. BSIR. British Society of Interventional Radiology.
ROST – Registry of oesophageal stenting, fi rst report
2004. Henley-on-Thames: Dendrite Clinical Systems;
2004. ISBN 1-903968-11-9.
12. Song HY, Shin JH, Yoon CJ, et al. A dual expandable
nitinol stent: experience in 102 patients with malignant gastroduodenal strictures. J Vasc Interv Radiol.
2004;15:1443–9.
13. Song GA, Kang DH, Kim TO, et al. Endoscopic stenting in patients with recurrent malignant obstruction
after gastric surgery: uncovered versus simultaneously deployed uncovered and covered (double) selfexpandable metal stents. Gastrointest Endosc.
2007;65:782–7.
694 Current Designs of Self-Expanding Stents
14. Isayama H, Kawabe T, Nakai Y, et al. Management of
distal malignant biliary obstruction with the ComVi
stent, a new covered metallic stent. Surg Endosc.
2010;24:131–7.
15. Moon CM, Kim TI, Lee MS, et al. Comparison of a
newly designed double-layered combination covered
stent and D-weave uncovered stent for decompression
of obstructive colorectal cancer: a prospective multicenter study. Dis Colon Rectum. 2010;53:1190–6.
16. Kim YW, Choi CW, Kang DH, et al. A double-layered
(comvi) self-expandable metal stent for malignant
gastroduodenal obstruction: a prospective multicenter
study. Dig Dis Sci. 2011;56:2030–6.
17. Tanaka T, Takahashi M, Nitta N, et al. Newly developed biodegradable stents for benign gastrointestinal
tract stenoses: a preliminary clinical trial. Digestion.
2006;74:199–205.
18. Fry SW, Fleischer DE. Management of a refractory
benign esophageal stricture with a new biodegradable
stent. Gastrointest Endosc. 1997;45:179–82.
19. Zilberman M, Nelson KD, Eberhart RC. Mechanical
properties and in vitro degradation of bioresorbable
fi bers and expandable fi ber-based stents. J Biomed
Mater Res B Appl Biomater. 2005;74:792–9.
20. Repici A, Vleggaar FP, Hassan C, et al. Ef fi cacy and safety
of biodegradable stents for refractory benign esophageal
strictures: the BEST (Biodegradable Esophageal Stent)
study. Gastrointest Endosc. 2010;72:927–34.
21. Janik V, Horak L, Hnanicek J, Malek J, Laasch HU.
Biodegradable polydioxanone stents: a new option for
therapy-resistant anastomotic strictures of the colon.
Eur Radiol. 2011;21(9):1956–61.
22. Petrtyl J, Bruha R, Horak L, Zadorova Z, Dosedel J,
Laasch HU. Management of benign intrahepatic bile
duct strictures: initial experience with polydioxanone
biodegradable stents. Endoscopy. 2010;42(Suppl 2):
E89–90.
23. Stivaros SM, Williams LR, Senger C, Wilbraham L,
Laasch HU. Woven polydioxanone biodegradable
stents: a new treatment option for benign and malignant
oesophageal strictures. Eur Radiol. 2010;20:1069–72.
24. Laukkarinen J, Sand J, Leppiniemi J, Kellomaki M,
Nordback I. A novel technique for hepaticojejunostomy for nondilated bile ducts: a purse-string anastomosis with an intra-anastomotic biodegradable biliary
stent. Am J Surg. 2010;200:124–30.
25. Szegedi L, Gal I, Kosa I, Kiss GG. Palliative treatment of esophageal carcinoma with self-expanding
plastic stents: a report on 69 cases. Eur J Gastroenterol
Hepatol. 2006;18:1197–201.
26. Fukumoto R, Orlina J, McGinty J, Teixeira J. Use of
Poly fl ex stents in treatment of acute esophageal and
gastric leaks after bariatric surgery. Surg Obes Relat
Dis. 2007;3:68–71, discussion 71–62.
27. Karbowski M, Schembre D, Kozarek R, Ayub K, Low
D. Poly fl ex self-expanding, removable plastic stents:
assessment of treatment ef fi cacy and safety in a
variety of benign and malignant conditions of the
esophagus. Surg Endosc. 2008;22:1326–33.
28. Ott C, Ratiu N, Endlicher E, et al. Self-expanding
Poly fl ex plastic stents in esophageal disease: various
indications, complications, and outcomes. Surg
Endosc. 2007;21:889–96.
29. Dua KS, Vleggaar FP, Santharam R, Siersema PD.
Removable self-expanding plastic esophageal stent
as a continuous, non-permanent dilator in treating
refractory benign esophageal strictures: a prospective
two-center study. Am J Gastroenterol. 2008;103:
2988–94.
30. Pennathur A, Chang AC, McGrath KM, et al. Poly fl ex
expandable stents in the treatment of esophageal disease: initial experience. Ann Thorac Surg.
2008;85:1968–72, discussion 1973.
31. Blomberg J, Wenger U, Lagergren J, et al. Antire fl ux
stent versus conventional stent in the palliation of distal esophageal cancer. A randomized, multicenter
clinical trial. Scand J Gastroenterol. 2009;45:208–16.
32. Nunes CC, Waechter FL, Sampaio JA, Pinto RD,
Alvares-Da-Silva MR, Pereira-Lima L. Comparative
post-operative study of prostheses, with and without
an anti-re fl ux valve system, in the palliative treatment
of esophageal carcinoma. Hepatogastroenterology.
1999;46:2859–64.
33. Osugi H, Lee S, Higashino M, et al. Usefulness of
self-expandable metallic stent with an antire fl ux
mechanism as a palliation for malignant strictures at
the gastroesophageal junction. Surg Endosc. 2002;16:
1478–82.
34. Homs MY, Wahab PJ, Kuipers EJ, et al. Esophageal
stents with antire fl ux valve for tumors of the distal
esophagus and gastric cardia: a randomized trial.
Gastrointest Endosc. 2004;60:695–702.
35. Wenger U, Johnsson E, Arnelo U, Lundell L,
Lagergren J. An antire fl ux stent versus conventional
stents for palliation of distal esophageal or cardia cancer: a randomized clinical study. Surg Endosc.
2006;20:1675–80.
36. Power C, Byrne PJ, Lim K, et al. Superiority of antire fl ux stent compared with conventional stents in the
palliative management of patients with cancer of the
lower esophagus and esophago-gastric junction:
results of a randomized clinical trial. Dis Esophagus.
2007;20:466–70.
37. Hirdes MM, Vleggaar FP, Laasch HU, Siersema PD.
Technical feasibility and safety of a new, implantable
re fl ux control system to prevent gastroesophageal
re fl ux in patients with stents placed through the
lower esophageal sphincter (with video). Gastrointest
Endosc. 2012;75(1):174–178.
38. Park S, Cheon JH, Park JJ, et al. Comparison of
ef fi cacies between stents for malignant colorectal
obstruction: a randomized, prospective study.
Gastrointest Endosc. 2010;72:304–10.
39. Saleem A, Baron TH, Gostout CJ. Large-diameter
therapeutic channel duodenoscope to facilitate simultaneous deployment of side-by-side self-expandable
metal stents in hilar cholangiocarcinoma. Gastrointest
Endosc. 2010;72:628–31.
40. Chahal P, Baron TH. Expandable metal stents for
endoscopic bilateral stent-within-stent placement for
malignant hilar biliary obstruction. Gastrointest
Endosc. 2010;71:195–9.
Part 3
Overview of Available Prostheses
Esophageal Prostheses
Massimo Conio and Antonella De Ceglie
5
Self-expandable metal stents (SEMS) represent a
major breakthrough in the endotherapy fi eld.
Esophageal SEMS have acquired a pivotal role in
palliation of malignant dysphagia due to
esophageal-esophagogastric junction cancers
(EC-EGJC) and mediastinal malignancy. Newly
available SEMS have been proven safe and effective in relieving such distressing symptoms [ 1– 3 ]
to include dysphagia and chest pain. SEMS
improve the quality of life (QoL) of these patients,
allowing better nutrition intake which prevents
dehydration and aspiration [ 4– 6 ] .
Recanalization of the esophageal lumen can
be also achieved by other methods such as laser,
argon plasma coagulation, and brachyradiotherapy with or without chemotherapy [ 7, 8 ] .
However, chemoradiation therapy alone, as primary treatment, can improve dysphagia but
requires several weeks. Randomized trials have
shown similar ef fi cacy for SEMS and brachytherapy with the consistent result that dysphagia
improved more rapidly after stent placement,
but the duration of relief was longer after
brachytherapy [
M. Conio , M.D. ()
Department of Gastroenterology and Digestive
Endoscopy , General Hospital Sanremo ,
C.so Garibaldi 187, 3 , Sanremo (IM) 18038 , Italy
e-mail: mxconio@libero.it
A. De Ceglie , M.D.
Department of Gastroenterology and Digestive
Endoscopy , Cancer Institute Giovanni Paolo II ,
Bari , Italy
9– 11 ] .
While the role of stents in palliation of malignant
strictures has been well established, their use in
benign strictures has gained increasing acceptance
in the last few years. Severe dysphagia can occur
with benign esophageal strictures following
radiotherapy, caustic ingestion, peptic injury, and
surgery. Placement of a stent in benign strictures is
challenging and sometimes risky [ 12, 13 ] .
Endoscopic dilatation with bougies or throughthe-scope (TTS) balloons is the standard treatment
for such lesions, but in 10% of patients who
develop refractory and recurrent strictures, the
temporary placement of a stent should be considered [ 14– 23 ] . In addition, stents have also been
proven effective in management of esophagorespiratory fi stula (ERF), anastomotic leaks, and ruptures. Their use has also been promulgated for
patients with bleeding esophageal varices [ 24– 26 ] .
This chapter describes the esophageal stents currently used for malignant and benign conditions.
Available Esophageal Stents
In the United States, the Food and Drug
Administration (FDA) has approved esophageal
metal stents for palliation of malignant dysphagia:
Ultra fl ex stent (Boston Scienti fi c, Natick, MA,
USA); Niti-S stent (Taewoong Medical, Seoul,
Korea); Evolution stent (Cook Medical, Winston
Salem, NC, USA); Alimaxx-ES (Merit Medical
System); Esophageal Z-stent (Cook Medical,
Winston Salem, NC, USA); Dua antire fl ux (Cook
Medical, Winston Salem, NC, USA); Wall fl ex ®
R. Kozarek et al. (eds.), Self-Expandable Stents in the Gastrointestinal Tract,
DOI 10.1007/978-1-4614-3746-8_5, © Springer Science+Business Media New York 2013
73
74
M. Conio and A. De Ceglie
(Boston Scienti fi c, Natick, MA, USA), and
Bonastent
®
(Standard Sci Tech, Seoul, Korea).
Additional stents are currently available in Europe,
including Hanaro stent and Choo stent (MI Tech,
Seoul, South Korea), the ENDO-FLEX (GmbH,
Voerde, Germany), and the FerX-ELLA and
SX-ELLA stent (ELLA-CS, Hradec Kralove,
Czech Republic). A biodegradable version of
ELLA is also available. Table 5.1 displays the
variety of SEMS that are marketed. Figure 5.1
shows the most commonly used SEMS types.
Both in Europe and the United States, a removable, fully covered, self-expanding plastic stent
(SEPS), the Poly fl ex (Boston Scienti fi c, Natick,
MA, USA), has been introduced as an alternative
to SEMS. Because of its removability, the FDA
has approved it for benign disease.
We have summarized the technical characteristics of the most commonly available selfexpanding metal and plastic stents:
Ultra fl ex stent (Boston Scienti fi c, Natick, MA, •
USA) is a partially covered SEMS with a mesh
knitted from a single elastic wire of nitinol. It
is mounted with a long thread that holds the
compressed stent. The end of the thread is
pulled through the catheter lumen to the oppo-
site end of the catheter and tied to a plastic
ring. The stent is released by pulling the
thread. There are four radiopaque markers.
The inner 2 markers indicate the fi nal position
of the covered part of the deployed stent and
the outer 2 the position of the uncovered
portion.
Wall fl ex •
®
(Boston Scienti fi c, Natick, MA,
USA) is a partially or fully covered stent constructed of multiple braided wires with an
internal silicone covering and uncoated fl anges
on both ends. The fully covered esophageal
Wall fl ex presents the silicone covering extending over the full length of the stent. The presence of progressive step fl ared ends creates a
wedge at either end to reduce the migration.
Niti-S stent (Taewoong Medical, Seoul, Korea) •
is composed of a single thread of 0.2-mm
nitinol wire and an inner polyurethane layer.
The stent is delivered in a compressed form
inside an introducer sheath of 4 mm in diameter. The company also produces esophageal
SEMS with a delivery system of 10 F that can
be introduced through the operative channel
of a therapeutic endoscope. To prevent migration, the stent has a dog-bone shape: the diam-
eter of the body can be 16, 18, and 20 mm,
while that of both ends can be 24, 26, and
28 mm . Another characteristic is the conform-
ability, as the stent adapts to the morphology
of the stricture after its release.
For cancer involving the distal esophagus and •
the esophagogastric junction, there is a Niti-S
double stent, with a double-layer con fi guration
over the body, consisting of an inner polyurethane layer (covering the whole stent) and an
outer uncovered nitinol wire. The ingrowth of
the malignant tissue through the mesh of this
outer wire is thought to prevent migration of
the stent into the stomach. The Conio stent is
a modi fi ed Niti-S prosthesis for hypopharyngeal strictures; it is characterized by small
diameters (12, 14, and 16 mm in the body; 14,
16, and 18 mm for the fl ared upper end), and
the available lengths are 8, 10, and 12 cm.
Evolution •
®
stent (Cook Endoscopy, Limerick,
Ireland) is made of a single nitinol wire, and it
is preloaded on a gun-like delivery system.
The stent can be recaptured before it has been
completely deployed. In November 2010, the
Evolution ® Controlled Release Esophageal
Fully Covered Stent was approved by the
FDA. This stent is characterized by an inner
and outer silicone layer that resists tumor
ingrowth. Another type of fully covered
Esophageal Z-Stent with a DUA antire fl ux
valve (Cook Endoscopy, Winston Salem, NC,
USA) is also available.
Alimaxx-E (Alveolus, Charlotte, NC, USA) is •
a laser-cut stent from a nitinol tube and fully
covered with polyurethane. Small metal struts
project from the outer part of the stent to avoid
migration. It can be placed over a guide wire
in the esophagus. In March 2009, Merit
Medical Systems, Inc. (South Jordan, Utah,
USA) acquired the products formerly manufactured and distributed by Alveolus, and the
Alimaxx-ES™ is the stent now produced.
SX-ELLA stent (ELLA-CS, Hradec Kralove, •
Czech Republic) is a SEMS composed of