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23315 Self-Expanding Metallic Stents for Malignant Hilar Biliary Obstruction
12. Vienne A, Hobeika E, Gouya H, et al. Prediction of
drainage effectiveness during endoscopic stenting of
malignant hilar strictures: the role of liver volume
assessment. Gastrointest Endosc. 2010;72:728–35.
13. Levy MJ, Baron TH, Gostout CJ, et al. Palliation of
malignant extrahepatic biliary obstruction with plastic
versus expandable metal stents: an evidence-based
approach. Clin Gastroenterol Hepatol. 2004;2:273–85.
14. Coelho-Prabhu N, Baron TH. Endoscopic retrograde
cholangiopancreatography in the diagnosis and management of cholangiocarcinoma. Clin Liver Dis.
2010;14:333–48.
15. Kozarek RA. Malignant hilar strictures: one stent or
two? Plastic versus self-expanding metal stents? The
role of liver atrophy and volume assessment as a predictor of survival in patients undergoing endoscopic
stent placement. Gastrointest Endosc. 2010;72:736–8.
16. Freeman ML, Sielaff TD. A modern approach to
malignant hilar biliary obstruction. Rev Gastroenterol
Disord. 2003;3:187–201.
17. Raju RP, Jaganmohan SR, Ross WA, et al. Optimum
palliation of inoperable hilar cholangiocarcinoma:
comparative assessment of the ef fi cacy of plastic and
self-expanding metal stents. Dig Dis Sci.
2011;56:1557–64.
18. Perdue DG, Freeman ML, Disario JA, et al. Plastic
versus self-expanding metallic stents for malignant
hilar biliary obstruction: a prospective multicenter
observational cohort study. J Clin Gastroenterol.
2008;42:1040–6.
19. Wagner HJ, Knyrim K, Vakil N, et al. Plastic endoprostheses versus metal stents in the palliative
treatment of malignant hilar biliary obstruction.
A prospective and randomized trial. Endoscopy.
1993;25:213–8.
20. Okamoto T, Fujioka S, Yanagisawa S, et al. Placement
of a metallic stent across the main duodenal papilla
may predispose to cholangitis. Gastrointest Endosc.
2006;63:792–6.
21. Neal CP, Thomasset SC, Bools D, et al. Combined
percutaneous-endoscopic stenting of malignant biliary obstruction: results from 106 consecutive procedures and identi fi cation of factors associated with
adverse outcome. Surg Endosc. 2010;24:423–31.
22. Dumas R, Demuth R, Buckley M, et al. Endoscopic
bilateral metal stent placement for malignant hilar
stenoses: identi fi cation of optimal technique.
Gastrointest Endosc. 2000;51:334–8.
23. 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.
24. Kawamoto H, Tsutsumi K, Harada R, et al.
Endoscopic deployment of multiple JOSTENT
SelfX is effective and safe in treatment of malignant
hilar biliary strictures. Clin Gastroenterol Hepatol.
2008;6:401–8.
25. Kim JY, Kang DH, Kim HW, et al. Usefulness of
slimmer and open-cell-design stents for endoscopic
bilateral stenting and endoscopic revision in patients
with hilar cholangiocarcinoma (with video).
Gastrointest Endosc. 2009;70:1109–15.
26. Lee JH, Kang DH, Kim JY, et al. Endoscopic bilateral
metal stent placement for advanced hilar cholangiocarcinoma: a pilot study of a newly designed Y stent.
Gastrointest Endosc. 2007;66:364–9.
27. Chahal P, Baron TH. Expandable metal stents for
endoscopic bilateral stent-within-stent placement for
malignant hilar biliary obstruction. Gastrointest
Endosc. 2010;72:628–31.
28. Ridtitid W, Rerknimitr R, Janchai A, et al. Outcome
of second interventions for occluded metallic stents in
patients with malignant biliary obstruction. Surg
Endosc. 2010;24:2216–20.
29. Kahaleh M, Mishra R, Shami VM, et al.
Unresectable cholangiocarcinoma: comparison of
survival in biliary stenting alone versus stenting
with photodynamic therapy. Clin Gastroenterol
Hepatol. 2008;6:290–7.
30. Ortner ME, Caca K, Berr F, et al. Successful photodynamic therapy for nonresectable cholangiocarcinoma:
a randomized prospective study. Gastroenterology.
2003;125:1355–63.
31. Dumoulin FL, Gerhardt T, Fuchs S, et al. Phase II
study of photodynamic therapy and metal stent as palliative treatment for nonresectable hilar cholangiocarcinoma. Gastrointest Endosc. 2003;57:860–7.
32. Gerhardt T, Rings D, Höblinger A, et al. Combination
of bilateral metal stenting and trans-stent photodynamic therapy for palliative treatment of hilar cholangiocarcinoma. Gastroenterol. 2010;48:28–32.
Biliary Malignancy: Distal
Dong Ki Lee
An unresectable distal malignant bile-duct
lesion is the best indication for a self-expanding
metal stent (SEMS). The emergence of SEMS
was a turning point in endoscopic biliary drainage because most clinical trials failed to demonstrate improvement in the patency using plastic
stents (PS). Considering that effective biliary
drainage is the most important factor determining quality of life, developing and improving
the performance of SEMS affects treatment
outcome because patients with malignant biliary obstruction generally have a shorter life
expectancy.
Although SEMS have a more prolonged
patency than that of PS and are considered to be
the fi rst choice for unresectable malignant biliary obstruction, they still have problems and
limitations, requiring further improvement.
Treatment outcomes, complications, and ongoing trials of SEMS have been described for distal
malignant duct lesions. Many clinical trials on
SEMS extend over a span of 20 years, and
improvements in techniques over time may
in fl uence differences between studies. Thus,
studies mostly published after the year 2000 will
be discussed.
D. K. Lee , M.D., Ph.D. (*)
Department of Internal Medicine, Gangnam Severance
Hospital , Yonsei University , 712 Eonjuro , Gangnam-gu ,
Seoul 135-720 , Republic of Korea
e-mail: gidept@chollian.net
1 6
Outcomes
Although design and material modi fi cations, as
well as many other efforts to prolong stent
patency, have not greatly affected the patency of
PSs, efforts are currently underway to improve
the performance of SEMS.
Plastic Versus SEMS
When SEMS were fi rst introduced, even prototypes demonstrated more prolonged patency than
PS. Although PS have been used in clinical practice since 1979 [ 1 ] , the only strategy found to
reliably prolong stent patency was the use of
larger caliber stents. This fi nding led to the use of
SEMS technology. Newer SEMS had fewer complications with prolonged patency due to improvements in the delivery system, fewer deployment
problems, and the addition of various designs.
The larger internal caliber of SEMS lead to a prolonged median stent patency of 9 months, as
con fi rmed in several prospective studies [ 2, 3 ] .
According to a meta-analysis of seven studies
that compared PS to the Wallstent® (Boston
Scienti fi c, Natick, MA, USA), from the 1990s
until the early 2000s, no difference was observed
between metal and PS in terms of technical success, therapeutic success, or complications [ 4 ] .
However, metal stents had a signi fi cantly reduced
relative risk (RR) of recurrent biliary obstruction
prior to death/end of study (RR, 0.52; 95%
R. Kozarek et al. (eds.), Self-Expandable Stents in the Gastrointestinal Tract,
DOI 10.1007/978-1-4614-3746-8_16, © Springer Science+Business Media New York 2013
235
236
D.K. Lee
con fi dence interval [CI], 0.39–0.69). Importantly,
a signi fi cantly reduced risk of recurrent biliary
obstruction was observed at the early time point
of 4 months (RR, 0.44; 95% CI, 0.3–0.63;
p < 0.01) with metal stents. Two studies reported
a higher number of endoscopic retrograde cholangiopancreatographies (ERCPs) per patient in
the PS group (mean 1.6 vs. 1.0 per patient).
In a multicenter randomized study [
5 ] com-
paring SEMS and a 10-Fr PS, the probability of
stent occlusion was 2.8-fold greater for PSs than
for SEMS and the overall complication rate was
signi fi cantly lower in the SEMS group versus the
PS group (20 vs. 31%; p < 0.05).
Most studies have con fi rmed that SEMS patency is twice as long as that of PSs, with a
decreased need for hospital readmission and
endoscopic re-intervention for recurrent biliary
obstruction. The prolonged patency offered by
SEMS often avoids the need for repeated ERCP
in patients with relatively prolonged survival and
who outlive the patency of their PS. However, PS
are preferred in patients with short predicted survival (< 6 months). In a randomized study from
Sweden [ 6 ] , the median survival of patients was
4.5 months; 65% of patients in the SEMS group
and 49% in the polyethylene group died before
stent failure.
A review of randomized controlled trials suggests that SEMS are associated with improved
patency over PS, as early as 4 months after insertion. The additional initial cost of metal stents is
offset by the reduction in re-intervention rates in
patients who have prolonged survival [ 7 ] . Thus,
metal stents appear to be more cost effective than
PS if the patient survives beyond 4–6 months.
This is applicable in countries where the cost of
ERCP is low compared with that of a metal stent
[ 8 ] . To conclude, a SEMS is the best choice for
treating patients with unresectable distal malignant biliary obstruction, except those whose
remaining life expectancy is very short.
Bare Versus Covered SEMS
Covered self-expandable metal stents (CSEMS)
are used for middle and distal bile-duct lesions,
because the covered membrane does not block
the opening of the intrahepatic duct and the stent
must overlap with the lesion by approximately
2 cm. Theoretically, because CSEMS block
tumor ingrowth, they were thought to offer more
prolonged patency than bare SEMS. However,
actual clinical data do not con fi rm this. Reasons
include the higher migration rate and more frequent impaction of sludge or food material within
CSEMS versus that of the bare type. After insertion of a bare SEMS, the metal mesh becomes
embedded into the bile-duct tissue, lining the bile
duct with tissue, causing far less attachment and
formation of sludge. SEMS are more prone to the
formation of sludge than the bare type when food
materials are impacted at the distal tip of the stent
and are a nidus for sludge formation. Additionally,
the tight stricture occasionally restricts full
expansion of a CSEMS because of the covered
membrane. Thus, the stent lumen may remain
restricted, making it more prone to obstruction
from biliary sludge [ 3 ] .
Clinical trials have been numerous, but there
is likely a trade-off, for the cause of stent occlusion, from tissue ingrowth and hyperplasia to
sludge formation resulting from the covering. For
these reasons, as shown in Table 16.1 [ 9– 14 ] ,
although there is a trend favoring covered SEMS,
overall stent patency rates between covered and
bare SEMS have not differed signi fi cantly to
date.
Two recent multicenter randomized trials
12, 13 ] , comparing uncovered and partially
[
covered SEMS in the palliation of distal malignant biliary obstruction, showed no difference
in time to recurrent biliary obstruction or patient
survival between the two groups. In one study
[ 12 ] , partially covered SEMS were more commonly associated with more serious adverse
events, particularly migration. However, that
study included patients between 2002 and 2008
and used the Wallstent, which has stronger axial
force. Another randomized study [
13 ] , which
divided 400 patients from 2006 to 2008 into two
groups, found no signi fi cant difference in stent
patency, patient survival time, or complication
rate between covered and uncovered nitinol
metal stents for the palliative treatment of
23716 Biliary Malignancy: Distal
Table 16.1 Studies comparing covered and uncovered self-expanding metal stents (SEMSs) for malignant distal
biliary obstruction
Stent obstruction (%)
Citation Study design Comparison Stent patency (days)
Isayama et al. 2004 [
Yoon et al. 2006 [
Park et al. 2006 [
Telford et al.
12 ]
2010 [
Kullman et al.
13 ]
2010 [
Gwon et al. 2010 [
PU , polyurethane; PC-PU , polycarbonate-polyurethane; PTFE , polytetra fl uoroethylene
a
Medium days to biliary obstruction
b
Largest value was censored
c
Cumulative stent patency rate at 3, 6, 9, and 12 months of the stent insertion
9 ] RCT PU Diamond (n = 57)
Diamond (n = 55)
10 ] Retrospective
cohort
11 ] Retrospective +
prospective cohort
RCT PU Wallstent (n = 68)
RCT PC-PU nitinol (n = 200)
14 ] Retrospective
cohort (percutaneous
insertion)
PU Wallstent (n = 36)
Wallstent (n = 41)
PU Wallstent (n = 98) 148.9 (3–667) 21 (21.4%)
Wallstent (n = 108) 143.5 (3–910) 20 (18.5%)
Wallstent (n = 61)
Nitinol (n = 200)
PTFE nitinol (n = 58)
Zilver (n = 58) + Sentinel
255 (11–1,155)
193 (12–810)
NS
245 ± 48
202 ± 29
357 (264–1,302)
711 (283 –
unknown
154
199
98/91/76/76
83/72/57/57
b
)
c
a
( p value)
8 (14%)
21 (38%)
(< 0.001)
9 (25.0%)
15 (36.6%)
20 (29%)
11 (18%)
47 (23.5%)
45 (22.5%)
7 (12.1)
19 (32.8)
(0.013)
malignant distal biliary obstructions. Clinical
data comparing SEMS patency according to
covering material is not available. However,
polyurethane is readily dissolved by bile acids
and tumor ingrowth.
SEMS Design
SEMS can be classi fi ed into three structural types
according to the manufacturing methods: braided,
specially braided, and laser-cut types. The metal
mesh of SEMS is classi fi ed as closed-cell and opencell types, based on the manufacturing method.
Furthermore, there are two types of metal (nitinol,
stainless steel) and three types of covering membrane
(silicone, polyurethane, e-PTFE). According to
these characteristics, SEMSs have different mechanical properties, including radial force, chronic outward force, force to recover to a straight position
after bending (axial force), and fl exibility. All of
these factors can affect clinical performance, such
as patency and complications [ 15 ] .
To date, there are few clinical data to compare
the ef fi cacy of SEMS based on design. Yang
et al. [ 16 ] compared double-woven SEMS
(Niti-D biliary uncovered stent, n = 41) with
single-woven SEMS (Wallstent, n = 60). The former SEMS is manufactured from nitinol and has
both a “hook-and-cross”-type wire structure to
create a D-shaped cavity at deployment and a
wide stent mesh. These characteristics were
intended to maximize fl exibility and conformability of the stent and to minimize stent shortening without loss of radial force. In contrast, the
Wallstent has a cross-type wire structure and a
tight stent mesh, which increases radial force.
The Wallstent has high axial force and low conformability. This study, however, showed no
signi fi cant difference in patency or complication
rates between the two groups. The Niti-D only
showed a signi fi cantly prolonged median duration of stent patency compared with the Wallstent
(249 days vs. 76 days; p = 006) in a hilar obstruc-
tion subgroup. Due to the small sample size and
nonrandomized, retrospective nature of the study,
it was not possible to explore the ef fi cacy and
complication rates between the two groups. Loew
et al. [ 17 ] compared 10-mm Zilver and 10-mm
Wallstents. Zilver is representative of the opencell type of SEMS, and Wallstents are closedcell-type SEMS. The mean number of days of
238
D.K. Lee
stent patency was 185.8 and 186.7, respectively,
and the occlusion rates were similar (23.9% vs.
21.4%). Earlier clinical trials [ 18, 19 ] comparing
the spiral Z-stent and the Wallstent and the Zilver
and Wallstent found no difference between the
stents in terms of technical success, stent occlusion, median patency rates, or complications.
Isayama et al. [
were ideal because they maintained appropriately
high values of radial force with less migration,
but exhibited extremely low axial force because
of their unique doubly overlapped structure.
Ingrowth is prevented by a thin e-PTFE membrane sandwiched between the two metal mesh
layers without being fi xed to the wires. However,
their clinical trial [ 20 ] failed to document the
superiority of this stent for managing distal malignant biliary obstructions. ComVi stents (n = 47)
were compared with the same number of covered
Wallstents, but no signi fi cant difference in stent
patency (208.1 + 173.3 vs. 151.1 + 130 days) or
stent occlusion (27.7% vs. 21.3%) was found.
However, there was a difference for the cause of
stent occlusion between the two groups. In the
ComVi group, the incidence of food impaction
was higher (14.9% vs. 2.1%; p = 0.0588) and that
of bile-duct kinking was lower than those in the
covered Wallstent group (0% vs. 8.4%; p = 0.1170).
The high incidence of food impaction was presumed to be due to the inner surface roughness of
the exposed wire. However, diet composition,
such as fi ber, may be a factor affecting stent
occlusion.
These studies showed that stent design is not
an important factor determining SEMS occlusion
rates. However, unlike the PS, in which the diameter of the stent is the only factor determining
stent patency, newly designed SEMSs promising
longer patency are awaiting clinical trials.
15 ] proposed that ComVi stents
SEMS Diameter
Most commercially available SEMSs are 10 mm
in diameter; thus, only a few studies have compared patency based on stent diameter. Loew
et al. [
17 ] compared the outcomes of 6-mm
Zilver, 10-mm Zilver, and 10-mm Wallstents.
At the interim analysis, a signi fi cant increase in
occlusions was noted in the 6-mm Zilver group at
the P = 0.04 level, resulting in arm closure, but
continued follow-up. The fi nal study arms
included 64, 88, and 89 patients receiving 6-mm
Zilver, 10-mm Zilver, and 10-mm Wallstents,
respectively. Stent occlusion occurred in 39.1,
23.9, and 21.4% of the cases, respectively. The
mean number of days of stent patency was 142.9,
185.8, and 186.7, respectively. SEMS occlusion
was much less frequent, but equivalent, in the
two 10-mm SEMS, despite major differences in
stent design and material, suggesting that diameter was a critical feature, as found for PSs.
Peroral Versus Percutaneous
Application
No reported study has directly compared percutaneous and peroral methods of SEMS insertion.
Nevertheless, treatment outcomes between
percutaneous and peroral methods are not
signi fi cantly different. Prolonged duration of
treatment and an increased rate of early complications due to formation of a percutaneous tract
have been reported. Numerous noncomparative
studies assessing percutaneous biliary drainage
and stenting (PTBD) and ERCP for treating distal bile-duct obstruction suggest no signi fi cant
difference in technical success rates between
percutaneous and endoscopic treatments [
Furthermore, complication rates and mortality
are comparable, although the type of complication differs. Pancreatitis is more often seen after
ERCP, whereas bile leakage is more frequently
seen after PTBD. An advantage of ERCP over
PTBD is the absence of a percutaneous drainage
tube, which can be uncomfortable for patients.
In clinical practice, the peroral method is preferred when the ampulla is endoscopically
approachable. However, if the peroral method fails
for any reason, the percutaneous method should
be attempted. Subsequent percutaneous stent
placement is successful in the majority of patients
in whom endoscopic stent placement fails [
21– 23 ] .
22 ] .
23916 Biliary Malignancy: Distal
Table 16.2 Causes of stent obstruction and complications: comparison of covered and uncovered self-expanding
metal stents (SEMSs) for malignant distal biliary obstruction
Citation Comparison
Isayama
et al. 2004 [
Yoon et al.
10 ]
2006 [
Park et al.
11 ]
2006 [
Telford et al.
12 ]
2010 [
Kullman et al.
13 ]
2010 [
Gwon et al.
14 ]
2010 [
a
% patients with gallbladder
CSEMS 0 4 2 2 5 1
9 ]
UCSEMS 16 (<0.001) 2 2 0 1 0
CSEMS 0 5 2 1 0 1
UC-SEMS 5 8 1 0 0 0
CSEMS 0 1 20 5 6 6
UC-SEMS 17 (.000) 0 3 (.000) 1 2 0 (.011)
CSEMS 6 3 4 3 (7%)
UC-SEMS 8 0 1 3 (7%) 1 0
CSEMS 9 18 12 2 3 6
UC-SEMS 21 10 4 2 4 0 (0.03)
CSEMS 0 1 4 1 0 2
UC-SEMS 14 1 4 0 0 0
Tumor ingrowth
( p value)
Tumor
overgrowth
Sludge/food
( p value) Cholecystitis Pancreatitis
a
0 6
Migration
( p value)
Surgery Versus SEMS
Only one reported study [ 24 ] has compared clini-
cal outcomes between surgical bypass (n = 40)
and endoscopic SEMS placement (n = 46) for the
palliation of patients with malignant distal common bile-duct obstruction. The SEMS group had
a lower rate of procedure-related mortality (2 vs.
7.5%; p = 0.01), a lower frequency of early complications (8.7 vs. 45%; p = 0.02), and a shorter
hospital stay (median 6 versus 12 days; p = 0.01).
Recurrent jaundice occurred in three patients in
the surgical bypass group (7.5%) and in eight
patients in the SEMS group (17.3%; p = 0.198).
Despite the early bene fi ts of stenting, no
signi fi cant difference in median overall survival
was found between the two groups.
Complications
Immediate, early, and late complications may occur
as a result of attempting to place SEMS [
Inadequate positioning of the stent, incomplete
removal of the covering membrane, failure of the
stent to expand, and the inability to remove the
introducing catheter after stent release are examples of problems that may occur during the
procedure. Malpositioning of SEMS is generally
25 ] .
attributed to operator error and may occur during
deployment of SEMS with a higher axial force.
Early complications, de fi ned as those occurring within the fi rst week after stent placement,
include stent migration, perforation, cholangitis,
and hemobilia. The most common late complication related to SEMS is stent occlusion. However,
these complications can occur at any time during
follow-up after SEMS placement, according to
the clinical situation. Table
16.2 [ 9– 14 ] details
the causes of obstruction and complications
between covered and uncovered metal stents.
SEMS Occlusion
The occlusion rate of SEMS during follow-up
appears to vary greatly among investigators and
stent types. Although SEMS have a lower occlusion rate and prolonged patency, and patients with
pancreas and biliary malignancies currently survive longer than historical controls, stent occlusion does occur while patients are alive. Several
studies [
the stent occlusion rate for both covered and
uncovered SEMS is between 20% and 38%.
after SEMS insertion are incomplete deployment,
food impaction, or a blood clot due to bleeding.
10, 11, 13, 16, 26– 28 ] have shown that
The causes of early occlusion within 7 days
240
D.K. Lee
Tumor ingrowth is the most common cause of late
occlusion in bare SEMS, whereas sludge is the
most common cause in CSEMS. In a postmortem
examination of ten patients with malignant biliary
obstruction who received polyurethane-covered
stents, only one case showed a small quantity of
protruding tumor tissue through a pinhole in the
polyurethane membrane [
29 ] . However, tumor
ingrowth is possible, due to membrane degradation by bile acids or the tumor itself, if CSEMS
are in place for longer than 6 months. No reported
study has been conducted on differences between
membrane materials.
Ingrowth is the most common cause of uncovered SEMS failure, particularly for smaller diameter SEMS. However, whether failures are, in
fact, caused by true tumor ingrowth is debated.
According to biopsies of ingrowth tissue performed by Loew et al. [ 17 ] , of the 40% of
ingrowth cases, half were caused by epithelial
hyperplasia. To date, most studies of ingrowth
were dependent on cholangiographic fi ndings.
Thus, misclassi fi cation may have occurred, causing a substantial underrepresentation of benign
tissue hyperplasia. SEMS occlusion caused by
tissue ingrowth is more likely to be benign epithelial hyperplasia in a narrower 6-mm stent than
with a 10-mm stent. However, the small number
of biopsy results in that study did not allow for
de fi nite conclusions concerning the exact tissue
characteristics causing ingrowth.
Tumor overgrowth can be the cause of occlusion in both types of SEMS. Thus, it is recommended that the stent be placed to overlap the
tumor-involved segment by approximately 2 cm
and no less than 1 cm.
It remains unclear which stricture-related or
stent-related factor(s) in fl uences stent patency. In
one multicenter study [ 30 ] , early stent expansion
(70% within 24 h) and easy passage of large-caliber instruments through the stricture were favorable for the long-term patency of Wallstents.
However, no signi fi cant difference in patency
rates according to patient age, initial serum bilirubin level, primary tumor type, length and morphological type of stricture, or length and location
of the distal end of the stent was found.
Theoretically, if tumor tissue is soft, the metallic
stent mesh can rapidly penetrate the tumor and
lead to early occlusion. However, this result could
be interpreted as indicating that the consistency
of most malignant biliary strictures is hard rather
than soft. A tight stricture may resist full expansion of a covered SEMS because of the covering
membrane. Thus, the covered stent lumen may
remain restricted and is, therefore, more prone to
obstruction by biliary sludge, similar to smaller
PSs, with a corresponding reduction in the overall covered SEMS stent patency [ 3 ] .
Management of Occluded SEMS
Therapeutic options for managing SEMS occlusion include mechanical cleansing using a basket
or balloons, insertion of a PS, or deployment of
another SEMS within the occluded metal stent.
Among these methods, regardless of the cause of
obstruction, re-occlusion is faster with mechanical cleansing than with re-stenting [ 31 ] .
Comparative studies [ 31– 34 ] between PSs and
SEMS revealed that SEMS generally have longer
patency than plastic stents. However, Yoon et al.
[ 35 ] reported that subsequent biliary drainage
with PSs offers similar patency and number of
additional biliary drainage procedures compared
with SEMS for managing occluded SEMS. Tumor
ingrowth, as with initial SEMS occlusion, was the
only factor associated with a shorter time to the
second stent occlusion, regardless of the material
used for the second stent. The initial SEMS
embedded in the tumor tissue and the tumor itself
may serve as a rigid framework, adding more
resistance to the expanding force of a subsequent
SEMS. If this is the case, a PS with its fi xed diameter may not be inferior to SEMS for subsequent
biliary stenting. Covered SEMS with suf fi cient
radial force may be useful in this setting.
Several studies have con fi rmed that covered
SEMS are superior to uncovered SEMS for reintervention. The fi rst extensive data from
Ornellas et al. [
paring covered SEMS placement as a primary
procedure versus re-intervention in malignant
biliary obstruction. The duration of stent patency
in the re-intervention group tended to be shorter
26 ] were presented, directly com-
24116 Biliary Malignancy: Distal
than that of the primary stent placement group,
although the difference was not statistically
signi fi cant. For the re-intervention group, patency rates at 3, 6, and 12 months were 90, 78, and
48%, respectively (100, 93, and 82%, respectively, in the primary placement group), which
were at or below the low end of the previously
reported ranges for primary stent placement. The
observed patency rates indicated that substantial
clinical bene fi t can be gained by re-intervention
with covered SEMS, as judged by the comparatively high patency rate through 6 months. Cho
et al. [
33 ] retrospectively evaluated patients who
underwent secondary biliary stent insertion for
prior biliary stent occlusion. The use of covered
SEMS at revision showed a signi fi cantly longer
patency than that of a PS, but not compared with
bare metal stents. A multivariate analysis showed
that bare SEMS had a worse cumulative stent patency and survival time than the use of covered
SEMS. With regard to patient age, causative disease, and antitumor treatment, bare SEMS had
2.0 times the risk of occlusion of CSEMS and 2.4
times the risk of death during follow-up compared with covered SEMS. They suggested that
SEMS placement using at least one covered
SEMS (in the primary and/or secondary procedure) might provide longer cumulative stent patency and survival than using uncovered SEMS
during both procedures.
Dislocation
Stent migration can occur both as a short-term
and as a long-term complication. SEMS migration rate has been reported to range from 0% to
12%, based on stent design and the presence of
covering material [
Migration after placement of uncovered SEMS
seems very rare. However, partially covered
SEMSs show a higher migration, of 4–12%.
Migration does not appear to be related to prior
PS placement or sphincterotomy [
et al. [
15 ] suggested that SEMS migration may
be related to increased axial force, which is high
in Wallstents. The axial force is the straightening
force exerted by high axial force, which may be
11, 13, 16, 26, 27, 36 ] .
37 ] . Isayama
associated with stent kinking and biliary wall
injury, as well as migration. Thus, a combination
of the covering and high axial force may lead to
stent migration. Currently, introducing SEMS
with low axial force and high conformability
results in very low migration rates, regardless of
the covering.
Cholecystitis
Acute cholecystitis is a rare complication in
patients managed with a PS, with an incidence of
0-1.6% [ 38– 42 ] . However, the incidence of
cholecystitis in patients treated with covered
SEMS varies from 0% to 11.5% [ 9, 26, 27, 29,
36, 43– 48 ] . In one report [ 49 ] , the most serious
complication of covered biliary stent placement
was acute cholecystitis, which occurred in 10%
of the cases and was responsible for one death.
The development of acute cholecystitis appears
to have been independent of cystic duct invasion
by the tumor and was observed only a few days
after stent insertion. Thus, the author believed
that the biliary stent was responsible, due to overlapping of the cystic duct ori fi ce.
However, no difference in cholecystitis
occurred between the covered and uncovered
SEMS insertion group (5.8% vs. 4.0% and 9.1%
and 10.4%, respectively) in two comparative
clinical studies [ 50, 51 ] . These studies suggested
that an obstruction by a tumor across the cystic
duct is the major determinant of cholecystitis
after SEMS insertion, regardless of stent type.
The onset of cholecystitis was 4.6 (range, 1–26)
days [ 50 ] . However, late-onset cholecystitis (99
and 123 days after SEMS insertion) was noted in
one study [
For a further explanation of these results,
Isayama et al. [
hypothesis. According to this, even if the cystic
duct ori fi ce is involved, bile fl ow is not obstructed
completely, but the ori fi ce may narrow and lose
elasticity. However, even a small amount of compression caused by stent expansion or a displaced
tumor may lead to impaired ef fl ux of gallbladder
bile. Cholecystitis can develop when gallbladder
bile is infected with gut bacteria intruding at
49 ] .
51 ] suggested an interesting
242
D.K. Lee
ERCP. In contrast, an intact cystic duct ori fi ce
may be elastic and allow space for bile from the
gallbladder to pass through.
A percutaneous cholecystostomy is the treat-
ment of choice for cholecystitis. Suk et al. [
50 ]
reported that a percutaneous cholecystostomy
should be performed as soon as cholecystitis is
diagnosed and that the clinical outcome was
good, with 87% (13/15) of patients recovering.
The remaining two patients underwent subsequent cholecystectomies.
Pancreatitis
In the majority of prior Wallstent studies, pancreatitis has ranged from 0% to 9% [ 9, 10, 16, 36,
49, 52 ] . These data are limited by small sample
size, and thus, they were unable to control for
known and potential confounding predictors of
post-ERCP pancreatitis. Pancreatitis is rare in
patients with pancreatic cancer because the pancreatic duct is usually already obstructed.
However, pancreatitis is possible by the following mechanisms: a larger diameter SEMS, in
conjunction with radial expansion after deployment, may cause obstruction of the pancreatic
ori fi ce or distortion of the common channel,
increasing the risk for post-ERCP pancreatitis.
This risk may be further exacerbated by CSEMS
through pancreatic ori fi ce occlusion.
Cote et al. [ 52 ] compared post-ERCP pancrea-
titis between 248 SEMS (102 covered) and 296
PS groups. The frequency of post-ERCP pancreatitis was signi fi cantly higher in the SEMS group
(7.3%) than that in the PS group (1.3%; OR, 5.7;
95% CI, 1.9–17.1). In a univariate analysis,
patient age of < 40 years, a history of post-ERCP
pancreatitis, and at least one pancreatic duct
injection were signi fi cant predictors of pancreatitis, whereas female gender and the presence of
pancreatic duct cancer were not. However, the
frequency of post-ERCP pancreatitis was similar
between covered (6.9%) and uncovered (7.5%)
SEMS (OR, 0.9; 95% CI, 0.3–2.4). Purported
SEMS-speci fi c risk factors, including the use of
CSEMS, overlapping SEMS, or undergoing a
biliary sphincterotomy, did not signi fi cantly
contribute to a higher risk. Percutaneous insertion
of SEMS also does not increase pancreatitis
[ 21, 53 ] . However, fully covered SEMS have
been reported to cause a higher rate (47%) of pancreatitis, and some cases (11.8%) lead to severe
pancreatitis [ 54 ] . Prompt removal of a SEMS can
avoid progression to severe pancreatitis when
post-ERCP pancreatitis occurs after SEMS placement, and symptoms persist or intensify.
Cholangitis
The frequency of cholangitis after SEMS placement ranges from 6.5% to 22% in reported series
[ 55– 60 ] . Restenosis and placement across the
main duodenal papilla are undoubtedly associated with the occurrence of cholangitis. In a recent
study [ 61 ] using barium, free re fl ux occurred
through the SEMS in all patients (Fig. 16.1 ).
However, re fl ux itself does not imply clinical
cholangitis. The presence of food material in the
bile-duct and stent blockage as a result of impacted
food can, nevertheless, be a cause of cholangitis.
In a study reported by Okamoto et al. [ 60 ] ,
Fig. 16.1 Re fl ux of contrast media into common bile
duct through the SEMS in a patient with pancreatic cancer
during hypotonic duodenography
cholangitis occurred in 12 of 108 patients (11.1%),
but more frequently in a subgroup with transpapillary stent placement (21.6%). Cholangitis can
also occur unrelated to stent occlusion [
Cholangitis, in this case, was treated successfully
with antibiotic therapy alone.
SEMS may be placed above the level of the
papilla, allowing the biliary sphincter to remain
intact. This avoids duodenal content re fl ux into
the bile duct and, consequently, may decrease the
incidence of cholangitis. However, this procedure
can only be undertaken with strictures when the
distal end is more than 2 cm above the papilla.
However, to date, there are no reported clinical
trials examining SEMS patency with regard to
stent position.
26, 49 ] .
Unusual Complications
Distal SEMS migration rarely causes duodenal
perforation [ 62 ] . When an excessive length of
SEMS is placed into the duodenum with resulting ulceration of the contralateral duodenal wall
or bleeding, argon beam plasma coagulation can
be used to trim the excess length [ 63, 64 ] .
Hemobilia can occur during SEMS placement
through a friable tumor. Such bleeding may produce clots and early stent obstruction requiring
endoscopic treatment [ 25 ] . The high expansive
force of SEMS has also been purported to cause
choledocho-duodenal fi stulas [ 65 ] .
SEMS fracture is another rare late complication
associated with periampullary malignant biliary
obstructions, which can also contribute to recurrent biliary obstruction. In a retrospective study
[ 66 ] , stent fractures were detected in 8% of patients,
most of them between 9 and 21 months after stent
placement, and all patients had a nitinol stent [ 67 ] .
Stent fracture was probably related to metal fatigue,
due to the constant and repetitive bending and
stress at the site of maximum leverage of the prosthesis. Nitinol stents may be stiffer than other bileduct non-nitinol stents and, therefore, less resistant
to bending. However, the paucity of stent fracture
data may suggest the possibility of manufacturer
failure of speci fi c stents.
24316 Biliary Malignancy: Distal
SEMS in Special Clinical Situations
SEMS Applications Based
on Resectability
The practice of placing SEMS in potentially
resectable patients is still evolving and is currently restricted to highly select patients. In light
of poor results with PS, preoperative biliary
drainage during the period of neoadjuvant treatment may be best achieved with metal stents,
which have a higher patency rate than PS and
do not affect surgical outcome, in contrast to
malignant hilar lesions [ 68– 70 ] . Furthermore,
shorter periods of drainage do not bene fi t outcomes [ 71 ] , and longer periods of drainage raise
the risk of stent occlusion, as well as the very
real possibility of closing the window of opportunity for cure in a patient with a potentially
resectable tumor. The prolonged patency and
removability of CSEMS makes them an attractive option for biliary decompression, regardless
of resectability. A strategy of initial covered
SEMS placement has been purported to be the
most cost-effective strategy for pancreatic malignancy regardless of resectability [ 72 ] . Covered
SEMS placement may be the best option for
cases of delayed surgery or if neoadjuvant therapy is being considered.
SEMS Insertion in a Duodenal
Obstruction
Endoscopic palliation can be achieved in patients
who require relief from both biliary and duodenal
obstruction, although this can be technically
dif fi cult to achieve, depending on the level of
duodenal obstruction in relation to the major
papilla [
iary drainage (EUSBD) with one-step placement
of a fully covered SEMS can be applied in
patients for whom endoscopic stent placement is
not possible because of tumor in fi ltration that
limits transpapillary access [
can substitute for percutaneous transhepatic
73 ] . Endoscopic ultrasound-guided bil-
74– 79 ] . This method