Role of Pancreatic Stents in Prevention of Post

Martin L Freeman
University of Minnesota, Division of Gastroenterology, Hennepin County Medical Center.
Minneapolis, MN, USA
Post-ERCP pancreatitis remains the most
common complication of ERCP, and is one
which can occasionally be devastating or
fatal. Once thought to be unpredictable and
inevitable, pancreatitis after ERCP has been
the subject of evolved understanding.
Increasingly, combinations of patient and
procedure-related risk factors allow fairly
accurate prediction of likelihood that an
individual patient will develop pancreatitis [1,
2, 3, 4, 5, 6, 7, 8]. Careful endoscopic
cannulation and therapeutic technique only go
so far in preventing pancreatitis, and are not
alone adequate to prevent this complication.
Pharmacologic prevention is either ineffective
or impractical [2].
Placement of trans-sphincteric pancreatic
stents is a relatively new and increasingly
adopted approach to reduce the risk of post-
ERCP pancreatitis. The mechanism by which
they work is not clearly understood. In theory,
stents serve to preserve flow of pancreatic
juice
after
pancreatic
sphincter
instrumentation, and/or to empty the gland of
reactive enzyme substrate. According to this
“plumbing” concept, drainage of manipulated
pancreatic ducts prevents pancreatitis just as
drainage of obstructed bile ducts prevents
cholangitis. While the evidence accumulates
from increasing numbers of studies at tertiary
centers that placement of pancreatic stents is a
highly effective method to reduce the
incidence and severity of post-ERCP
pancreatitis, and this practice has become
standard at many large referral centers in the
United States and elsewhere, the adoption of
pancreatic stenting into community practice
and even some advanced centers has been
limited.
Many issues remain unanswered:
Which individual patients are at
sufficiently high risk to warrant a stent?
What are the consequences of failure at
attempted stent placement?
Are success rates and efficacy of
pancreatic stent placement as good in the
hands of those with limited experience?
And how serious and preventable is the
risk of inducing pancreatic duct injury by
placement of a stent?
Finally, should this technique become
standard for all endoscopists or should it be
limited to tertiary centers?
The evidence that pancreatic stent placement
reduces rates of post-ERCP pancreatitis in
high risk patients is substantial. Five
prospective randomized controlled trials
(three published in final form) and at least
seven case-control studies have compared
rates of pancreatitis after ERCP with and
without a pancreatic stent (Table 1) [9, 10,11,
12, 13, 14, 15, 16, 17, 18, 19, 20]. These
studies involved mixed high-risk groups
including precut sphincterotomy, sphincter of
Oddi dysfunction, difficult cannulation,
pancreatic sphincterotomy, biliary balloon
dilation for stone, ampullectomy and all
ERCP including attempted pancreatic stents.
Eleven of 12 studies, and all with more than
30 patients have shown either trends towards
reduced rates or statistically significantly
lower rates of post-ERCP pancreatitis in

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323
patients receiving pancreatic stents (range 0-
20%) compared to those without pancreatic
stents (range 6-67%); statistical significance
was reached in three of five randomized
controlled trials. [10, 14, 16]. A meta-analysis
of five prospective studies involving 483
patients showed that odds ratio of post-ERCP
pancreatitis without stents was three-fold
higher than for with pancreatic stents (15.5%
vs. 5.8%; OR: 3.2, 95% CI: 1.6 to 6.4) [21];
numbers needed-to-treat analysis showed that
one in every ten patients would benefit from
pancreatic duct stent placement. The major
limitation of the available studies is a lack of
analysis by intention-to-treat, in that patients
with failed pancreatic stent placement were
excluded, a group in whom pancreatitis rates
have been found to be high [15].
Overall, the effectiveness of pancreatic
stenting in reducing pancreatitis rates after
high-risk ERCP has been corroborated by
accumulating experience at advanced centers.
One retrospective study using historical
controls showed that in 436 patients treated
with biliary ± pancreatic sphincterotomy for
sphincter of Oddi dysfunction, pancreatitis
rates were typically high at 28.2% (5.4%
severe) in those undergoing simple pull-type
biliary sphincterotomy without a pancreatic
stent, compared with 13.5% (0.4% severe) in
those receiving biliary ± pancreatic
sphincterotomy with a pancreatic stent
Table 1. Studies of pancreatic stents in prevention of post-ERCP pancreatitis.
Author, year
Study design
Patients
No. of
cases
Pancreatitis rate
according to the
presence of
pancreatic stent
Significance
Without
With
Smithline, 1993 [17]
RCT
Precut biliary ES, SOD,
small ducts
93
18%
14%
P=0.299
Sherman, 1996 [16]
RCT (abstract)
Precut biliary ES
93
21%*
2%
P=0.036
Tarnasky, 1998 [10]
RCT
Biliary ES for SOD
80
26%
7%
P=0.03
Elton, 1998 [11]
Retrospective CC
Pancreatic ES for all
indications
194
12.5%
0.7%
P<0.003
Patel, 1999 [12]
RCT (abstract)
Pancreatic ES for SOD
36
33%
11%
P>0.05
Vandervoort, 1999 [18] Retrospective CC Pancreatic brush cytology for
suspected malignancy
42
28.1%
0%
P=0.08
Aizawa, 2001 [13]
Retrospective CC Biliary balloon dilatation for
stone
40
6%
0%
P=0.11
Fogel, 2002 [9]
Retrospective CC Biliary +/- pancreatic ES for
SOD
436
28.2%
13.5%
P<0.05
Norton, 2002 [19]
Retrospective CC
Endosopic ampullectomy
28
11.1%
20%
P>0.05
Fazel, 2003 [14]
RCT
Difficult cannulation, biliary
ES,SOD
76
28%
5%
P<0.05
Freeman, 2004 [15]
Retrospective CC All attempted major papilla
PD stents in high-risk
therapeutic ERCP
225
66.7%
14.4%
P=0.06
Catalano, 2004 [20]
Retrospective CC
Endoscopic ampullectomy
103
16.7%
3.3%
P=0.10
RCT: randomized controlled trial
CC: case-control
ES: endoscopic sphincterotomy
SOD: sphincter of Oddi dysfunction
PD: pancreatic duct
* control group in whom pancreatic stent removed immediately at end of procedure; excluded patients in whom
pancreatic stent could not be placed had pancreatitis rate of 13.8%

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324
(P<0.05); there was a tendency for
pancreatitis rates to be lower if a pancreatic
stent was placed prior to pancreaticobiliary
sphincterotomy (10.7%) than after (19.2%)
[9].
A striking finding from all of the published
studies, and from accumulating experience at
advanced centers at which pancreatic stents
are frequently used, is that risk of severe or
necrotizing pancreatitis was virtually
eliminated by a properly positioned pancreatic
stent. In all reported studies, including
approximately 1,500 high-risk ERCPs, over
half of which involved pancreatic stents, only
one case of severe pancreatitis was reported in
a patient receiving a pancreatic stent [9, 10,
11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21]. By
meta-analysis, odds of developing severe
pancreatitis were found to be 11.5 times lower
in patients receiving pancreatic stents [21].
Caveats of pancreatic stenting as a strategy to
prevent post-ERCP pancreatitis are
substantial, and have led to the inconsistent
adoption of this technique, even by some
experts. Most studies from expert centers
have reported failure rates of 5-10% of
pancreatic stent placement, especially in
patients with stenotic pancreatic orifices or
small and tortuous ducts, when using standard
techniques involving placement of a guide
wire deep into the pancreatic duct [10, 14,
17]. A recent study from our center confirmed
the suspicion that failed attempted pancreatic
stent placement was very risky, with two-
thirds of patients developing moderate or
severe pancreatitis - implying that pancreatic
stent placement should only be considered
when it can almost certainly be followed to
completion; this same study showed that
universal success at pancreatic stent
placement could be achieved by use of a
modified technique involving a small-caliber
0.018 inch diameter guidewire and short (2
cm) small-caliber stents in patients with small
or tortuous ducts [15]. Many practicing
endoscopists are unfamiliar with the specific
techniques required to achieve pancreatic
ductal access, especially the small caliber
guidewires (0.018 to 0.025 inch) that are
necessary to place the small caliber (3 or 4
French) stents that appear to be safest for
preventing ductal injury and prevention of
pancreatitis (Figure 1). Placement of
guidewires deep into the pancreatic duct may
require different techniques than into the bile
duct because of the tortuous course, and the
potential for passage of the wire tip out any of
the multiple sidebranches. Pancreatic stents
can be accidentally delivered entirely into the
duct, can later migrate inwards (especially
longer straight stents without a duodenal
pigtail, or those with two inner flanges) [22]
and can cause ductal perforation, all with
serious consequences.
Pancreatic ductal and parenchymal changes
induced by pancreatic stents are a concern, but
one which has been greatly reduced by use of
very small-caliber stents [23, 24, 25, 26, 27].
Ductal and parenchymal changes have been
observed in approximately one third to two
thirds of patients, sometimes after relatively
brief duration of stenting, and especially in
those with previously normal pancreatic
ducts. While most ductal changes resolve
spontaneously, the long-term outcome has not
been thoroughly investigated. Ductal changes
have been observed mostly in patients having
traditional flanged 5 or 7 French stents, which
may be of similar caliber to the native
pancreatic duct, are made of rigid
polyethylene, and have large pointed inner
flanges, all factors that may contribute to
Figure 1. 4 French pancreatic stent draining clear
pancreatic juice, placed after difficult cannulation and
biliary sphincterotomy.

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injury while present in the duct and during
stent removal. Recent data from a large
retrospective study suggest that unflanged,
longer 3 French stents with a single duodenal
pigtail were associated with substantially
reduced frequency of ductal changes (24% for
3 and 4 French stents compared with 80% for
5 and 6 French stents), and were not observed
to migrate inside the duct [23]. Three French
stents were also associated with slightly lower
rate of post-ERCP pancreatitis (7.5%)
compared with 5 French stents (9.8%
pancreatitis) or 6 French stents (14.6%). It is
possible but unknown whether stents made of
newer softer materials than the traditional
polyethylene, and with smaller inner flanges,
will also result in less duct injury.
All patients with pancreatic stents must
undergo specific follow-up to ascertain
spontaneous passage of the stent, or for
endoscopic removal in rare cases without
stent passage - these add cost and complexity
to the care of the patient, but one that seems
minor compared with cost and consequences
of managing even the occasional case of
severe post-ERCP pancreatitis. Because stent-
induced pancreatic injury may be related to
duration of stenting, it is necessary to either
document passage of pancreatic stents by
abdominal X-ray or perform endoscopic
removal, preferably within 2 to 4 weeks if
placed for prophylaxis. The spontaneous
passage rate of small caliber (3 French,
unflanged) pancreatic stents has been shown
to be substantially higher than for traditional
stents, with spontaneous stent passage
occurring in 86% of 3 French stents versus 65
to 73% of 4 to 6 French stents (P<0.001) [23].
Nasopancreatic drains have been proposed as
an alternative to pancreatic stenting, as they
can be removed without a repeat endoscopic
procedure [11]. These require placement of a
relatively large caliber (4 or 5 French) flanged
catheter to the relatively narrower duct in the
body or the tail of the pancreas, raising
concern for possible ductal injury.
Nasopancreatic drains are sometimes poorly
tolerated by patients and require overnight
hospitalization, limiting their utility.
Overall, pancreatic stenting appears to be very
promising strategy for prevention of post-
ERCP pancreatitis, and has dramatically
altered outcomes of high-risk ERCP at centers
utilizing this technique. At our center
consisting of two endoscopists who perform
ERCP, approximately 300 pancreatic stents
are placed annually for the purpose of
preventing post-ERCP pancreatitis. As such,
despite performance of mostly high-risk
ERCP including treatment of sphincter of
Oddi dysfunction, and complex pancreatic
and biliary therapy, we have found, like other
centers adopting this technique, that severe
post-ERCP has been virtually eliminated -
now approximately one in every 1,000 to
2,000 cases - and when it occurs, always
involving either omission of pancreatic stent
placement, or a very rare malfunction or duct
perforation from a poorly positioned
pancreatic stent. Despite use of pancreatic
stents, mild pancreatitis still occurs with some
frequency in high-risk patients, but is more of
a nuisance than a serious complication. Like
many others, we have shifted almost
exclusively to very small caliber stents - either
long (8-10 cm), single external pigtail, and
unflanged 3 French stents placed to the mid-
body, or in patients with small or tortuous
pancreatic ducts, we use 4 French straight
flanged but short (2 cm) stents made of a
softer material than conventional polyethylene
(Hobbs Medical, Inc., Stafford Springs, CT,
USA). Most importantly, we have found that
one type or size of pancreatic stent does not
suit all occasions, and that the stent must be
carefully chosen to match the diameter and
course of the duct. We place pancreatic stents
in all higher risk situations - especially
suspected sphincter of Oddi dysfunction -
after difficult cannulation, before precut
sphincterotomy, and after ampullectomy,
among others. We have found that accessing
the pancreatic duct with a guidewire, and
ability to subsequently place pancreatic stents
removes much of the fear and apprehension
from previously daunting cases, and has
allowed us to proceed with much greater
confidence and achieve near-universal success

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at achieving biductal access with advanced
techniques such as precut (access)
papillotomy and treatment of sphincter of
Oddi dysfunction, even under the most
challenging of situations such as after gastric
bypass with Roux-en-Y or previously failed
cannulation [28].
While pancreatic stent placement has
revolutionized the reduction of post-ERCP
pancreatitis, questions still remain
unanswered. It can still be difficult to decide
which individual patients and procedures are
at sufficiently high risk to warrant placement
of pancreatic stents. Most importantly, it is
unclear how well this technique will translate
outside major centers. Effectiveness and
safety of pancreatic stent placement by
community endoscopists would be expected
to be less than for advanced centers. A
multicenter outcome study of pancreatic stent
placement in a spectrum of practices would
give us a better sense of the ultimate
“effectiveness” as opposed to “efficacy” of
pancreatic stenting in preventing post-ERCP
pancreatitis. Ultimately, the best hope for
prevention of post-ERCP pancreatitis lies in
careful selection of patients for ERCP, with
avoidance of unnecessary or marginally
indicated cases by use of laparoscopic
cholangiography during cholecystectomy,
MRCP, and EUS [7]. Once ERCP is
undertaken, careful technique by experienced
endoscopist goes a long way, but not all the
way to prevent pancreatitis. It is our opinion
that pancreatic stenting does have potential to
greatly impact post-ERCP pancreatitis, and
that practicing endoscopists should either seek
specific updated training in the equipment and
techniques required for pancreatic stent
insertion, or refer patients at higher risk to
specialized centers with experience at
pancreatic stent insertion.
Keywords
Cholangiopancreatography,
Endoscopic
Retrograde;
Pancreatitis
/prevention and control; Stents
Correspondence
Division of Gastroenterology
Hennepin County Medical Center
University of Minnesota
701 Park Avenue
Minneapolis, MN 55415
USA
Phone: +1-612.873.8582
Fax: +1-612.904.4366
E-mail address: freem020@umn.edu
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