ORIGINAL ARTICLE

Management of Complications Associated with Partially CoveredBiliary Metal Stents

Henry Ho Æ Anshu Mahajan Æ Sonia Gosain Æ Animesh Jain Æ Andrew Brock ÆMichele E. Rehan Æ Kristi Ellen Æ Vanessa M. Shami Æ Michel Kahaleh

Received: 11 December 2008 / Accepted: 3 February 2009 / Published online: 7 March 2009

� Springer Science+Business Media, LLC 2009

Abstract Background Partially covered metal stents

(PCMS) have been increasingly used for both malignant and

benign biliary indications. This study reports their compli-

cations and subsequent management. Methods Over 5 years,

all patients receiving biliary PCMS were followed pro-

spectively until stent-related dysfunction or death. Data

were analyzed for the following variables: primary disease,

time until revision, and type and reason for revision. Results

PCMS were placed in 396 patients (247 with malignant

biliary strictures and 149 with benign biliary disease).

Complications were observed in 70 patients (18%), occur-

ring a mean time following placement of 159 days.

Duodenal migration occurred in 27 cases (6.8%), while

proximal migration occurred in 9 cases (2.3%). Cholecys-

titis was documented in 13 cases (3.3%). There were six

cases of stent occlusion due to debris or sludge (1.6%), four

cases of pancreatitis (1%), four cases of tumor overgrowth

(1%), three cases of benign stenosis in the uncovered portion

of the PCMS (0.8%), two cases of abdominal pain (0.5%),

one case of an infected biloma (0.3%), and one case of a liver

abscess (0.3%). Conclusions Major complications associ-

ated with PCMS placement include migration and

cholecystitis. Their management includes endoscopic revi-

sion, cholecystectomy, and gallbladder drainage. Further

improvements in the structure and composition of PCMS

may prevent these complications.

Keywords ERCP: Endoscopic retrograde

cholangiopancreatography � SEMS: Self-expanding metal

stent � PCMS: Partially covered self-expanding metal stent

Introduction

Endoscopic retrograde cholangiopancreatography (ERCP)

with placement of biliary stents has been used for more

than 2 decades [1, 2]. Because of their lower cost, wide

distribution, and ease of placement, plastic stents have been

conventionally used for benign biliary diseases and

malignant biliary obstruction with short-term survival [2].

Those patients with malignant distal biliary obstruction and

survival time beyond 6 months have been more frequently

treated with self-expandable metal stents (SEMS), given

their greater complication-free survival and cost-effec-

tiveness [3–6]. In an attempt to improve patency, however,

partially covered metal stents (PCMS) were developed to

resist tissue in-growth through the stent interstices [7, 8], a

well-demonstrated complication of uncovered metal stents

[9]. Indeed, the demonstration of PCMS removability [10,

11] has prompted expanded indications for their use to

include placement for distal pancreatico-biliary malig-

nancy regardless of resectability [12, 13].

With the increasing use of PCMS, though, several

complications have been reported, including migration [12,

14–16], benign strictures [7, 17] and cholecystitis [18, 19].

Given the limited prospective data regarding PCMS and

their wider use in malignant and benign biliary diseases,

we sought to evaluate the complications associated with

their use as well as their respective management.

Patients and Methods

Patients

A total of 423 patients underwent insertion of metal

stents in our institution over a 5-year period and were

H. Ho � A. Mahajan � S. Gosain � A. Jain � A. Brock �M. E. Rehan � K. Ellen � V. M. Shami � M. Kahaleh (&)

Digestive Health Center, University of Virginia Health System,

Charlottesville, Box 800708, VA 22908-0708, USA

e-mail: mk5ke@virginia.edu

123

Dig Dis Sci (2010) 55:516–522

DOI 10.1007/s10620-009-0756-x

followed prospectively; 27 patients received uncovered

SEMS and 396 received PCMS. All patients in the

uncovered SEMS group had malignant hilar lesions. In

the PCMS group, 247 patients presented with malignant

disease and 149 patients with benign disease. After stent

insertion, patients were followed in clinic with liver

function tests (LFTs) until stent removal (in cases of

benign diseases receiving PCMS), stent dysfunction, or

death. The study was approved by our institutional

review board; all patients provided written consent for

their procedures.

Methods

In the uncovered SEMS group, uncovered Wallstents (40,

60, or 80 mm length) of 10-mm diameter (Boston Scien-

tific, Natick, MA) were placed. In the PCMS group,

Wallstents (40, 60, or 80 mm length) of 10-mm diameter,

partially covered with Permalume� (Boston Scientific,

Natick, MA), were placed. Following biliary sphincterot-

omy, the origin of the cystic duct insertion was noted in

patients having a gallbladder. The PCMS delivery system

was advanced proximal to the lesion over a guidewire

where the PCMS was positioned and deployed. When

anatomically feasible, PCMS were deployed to avoid

occlusion of the cystic duct insertion when the gallbladder

was present. Removal of PCMS was effected using the

snare or rat tooth technique as previously published [10].

Proximal migration was managed with a combination of

CRE balloon dilation (Boston Scientific) and rat tooth

extraction (Figs. 1, 2, 3, 4, and 5).

Definition of Events

Successful PCMS placement was defined as deployment of

the PCMS across the lesion effecting biliary decompression

and relief of symptoms. Stent patency was defined by the

period of time between stent insertion and stent dysfunc-

tion. Stent occlusion, in contrast to tumor overgrowth or

stricture in the uncovered portions of the PCMS (hyper-

plasia), was defined as stent dysfunction secondary to

biliary debris or sludge. Complications were stratified as

early (occurring B30 days of PCMS placement) or late

(occurring [30 days following PCMS placement). Cho-

langitis was defined as fever persisting for 24 h in the

setting of biochemical cholestasis without another dis-

cernible cause. Cholecystitis was defined by appropriate

symptoms in the setting of supportive imaging (ultrasound,

computed tomography). We also distinguish duodenal from

proximal migration, hereto uncommonly cited in the

literature.

Repeat biliary intervention was defined as the need for any

type of endoscopic, percutaneous, or surgical procedure to

improve biliary drainage after insertion of the initial PCMS.

Fig. 1 Fluoroscopy showing CRE balloon dilation of a proximally

migrated PCMS

Fig. 2 Fluoroscopy showing the PCMS grasped from the inside using

a rat tooth forceps

Dig Dis Sci (2010) 55:516–522 517

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Results

A total of 70 patients (41 males, 29 females) with a mean

age of 59 developed complications (18%) in the PCMS

group. Complications were observed in 48 patients with

underlying malignancy and 22 patients with benign biliary

diseases (Table 1). The global mean time to complication

was 159 days with a range between 1 and 1,027 days.

Early Complications (B30 Days) of PCMS and

Management

Fourteen patients (3.5%) had early complications. Five

patients had benign disease, and nine patients had malig-

nant indications (Table 2). Complications included

duodenal migration (n = 3), proximal migration (n = 2),

cholecystitis (n = 4), pancreatitis (n = 2), stent occlusion

(n = 1), tumor overgrowth (n = 1), and abdominal pain

(n = 1).

All the patients who suffered from early cholecystitis

had underlying malignant disease. Two patients were noted

to have had the PCMS covering the cystic duct insertion,

one had tumor involvement of the cystic duct, and only one

had PCMS below the cystic duct. Three patients were

treated with percutaneous cholecystostomies, while one

patient had a gallbladder stent placed endoscopically.

Twelve patients underwent PCMS revision. Two

patients who experienced stent migration were managed by

Fig. 3 Fluoroscopy showing successful extraction of the PCMS from

the bile duct

Fig. 4 Fluoroscopy showing removal of the PCMS through the

working channel of the endoscope

Fig. 5 Cholangiogram post PCMS removal showing enlargement of

the bile duct post PCMS removal

518 Dig Dis Sci (2010) 55:516–522

123

removal and replacement with plastic stents, while the

other three underwent replacement with a PCMS. The

patient with early stent occlusion was found to have a large

amount of debris within the PCMS and was treated with

removal and replacement with new PCMS. The one patient

with early tumor overgrowth was also managed by

replacement with PCMS. The two patients with pancreatitis

and the one experiencing abdominal pain as a result of

PCMS placement had their PCMS removed.

Late Complications ([30 Days) of PCMS

and Management

Table 3 delineates the 56 patients with long-term compli-

cations, of which 19 had benign indications and 37 had

malignant ones. Migration was observed in 31 patients

(7.8%). Duodenal migration occurred in 24 cases (6.1%),

whereas proximal migration occurred in 7 cases (1.7%).

The management of migration included replacement with

PCMS (n = 14), replacement with plastic stents (n = 5),

removal (n = 7), stent within a stent (n = 3), or no inter-

vention (n = 2) secondary to spontaneous migration with

resolution.

The second most common long-term complication of

PCMS placement was cholecystitis (n = 9). In six

patients, the PCMS covered the cystic duct insertion.

There was cancer involvement of the cystic duct in one

patient, while two patients who had PCMS placed below

the cystic duct developed cholecystitis. Cholecystitis was

managed by cholecystectomy in six cases, percutaneous

drainage in two cases, and placement of a gallbladder

stent in one case.

Three patients developed late cholangitis. They had

duodenal cancer, ampullary adenoma, and benign stricture

and developed cholangitis at 873, 874, and 1,027 days,

respectively. All three patients had their PCMS removed,

while the patient with duodenal cancer underwent PCMS

replacement.

Tumor overgrowth (n = 3) was managed by replace-

ment with plastic stents in two cases and replacement with

PCMS in the other. We also report PCMS stricture in the

proximal uncovered portion of the stent in three patients

(Fig. 6), all of which were in benign disease; two were

managed with replacement with PCMS, while one patient

received plastic stents.

Pancreatitis occurring after PCMS placement was

managed with PCMS removal. One patient developed a

liver abscess 364 days after PCMS placement and was

treated with removal of PCMS and replacement with

plastic stents. Another patient developed an infected bilo-

ma, 106 days after PCMS placement, which was related to

a bile leak after cholecystectomy. This patient had removal

and replacement with PCMS. Lastly, one patient developed

abdominal pain 45 days after PCMS placement. This was

managed with PCMS removal only, since the benign bili-

ary stricture had resolved.

Table 2 Early complications of PCMS insertion

Reason for revision No. Mean time to revision (days)

Duodenal migration 3 3

Proximal migration 2 10

Cholecystitis 4 9

Tumor overgrowth 1 24

Stent occulusion 1 7

Pancreatitis 2 11

Abdominal pain 1 5

Table 3 Long-term complications of PCMS insertion

Reason for revision No. Mean time to revision

(days)

Duodenal migration 24 185

Proximal migration 7 113

Cholecystitis 9 97

Tumor overgrowth 3 215

Cholangitis 3 925

Stricture in uncovered portion 3 262

Stent occlusion 2 136

Pancreatitis 2 50

Abdominal pain 1 45

GB fossa abscess 1 106

Liver abscess 1 364

Table 1 Characteristics of patients at the time of PCMS insertion

Characteristics No.

No. of patients 70

Gender (male/female) 41/29

Mean age (years, range) 59 (23–89)

Primary disease

Pancreatic cancer 35

Benign stricture 20

Cholangiocarcinoma 4

Ampullary adenoma 3

Duodenal cancer 3

Bile leak 2

Pancreatic lymphoma 1

Gastric lymphoma 1

Ampullary carcinoma 1

Dig Dis Sci (2010) 55:516–522 519

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Discussion

Expandable biliary metal stents have been developed for

the treatment of malignant biliary strictures [3–6]. In the

past decade, partially covered self expandable metal stents

(PCMS) were developed to prevent tumor growth through

the mesh of the stent [20]. Experience with PCMS has been

reported by several groups [11, 17, 21–25].

PCMSs provide better biliary decompression than plas-

tic stents because of their larger diameter. In addition,

PCMSs have a metal composite covered by a synthetic

material, such as silicone, that resists the effects of bile,

gastric, or pancreatic secretions [26]. The covering is

designed to prevent tumor ingrowth [7, 8], while the 0.5-

mm uncovered portions at each end of the stent are meant

to prevent migration. Our group has a preference for PCMS

for distal biliary lesions, leaving the use of uncovered

SEMS for malignant hilar lesions of the biliary tree deemed

surgically unresectable. This explains the small number of

uncovered SEMS placed during the study period.

In the PCMS group, we encountered 36/396 cases

(9.1%) of migration in our study. Duodenal migration

accounted for 27 of these cases (6.8%). This is in the range

of what has been reported previously [15, 23, 27, 28]. We

also report, however, nine cases (2.3%) of proximal

migration of the PCMS. This is likely related to the fore-

shortening of the PCMS with mucosal overgrowth through

the uncovered portion of the SEMS, as previously inves-

tigated by our group [17]. Although this is a less common

mode of migration and less frequently reported by other

investigators, its endoscopic management is more chal-

lenging and requires the combination of balloon dilation

and rat tooth extraction (Figs. 1, 2, 3, 4, and 5). The mean

time to revision was 164 and 90 days for duodenal and

proximal migrations, respectively. All migration cases

were managed with endoscopic removal of the PCMS

except in three cases with malignancy undergoing place-

ment of a PCMS within the previously placed PCMS.

Inability to remove the PCMS is unusual in expert hands

but can be encountered when the PCMS has been in place

for more than 6 months [17] or when access to the mal-

functioning PCMS is precluded by malignancy, as

experienced in the three above patients.

Occlusion rates of PCMS have been reported between

5% and 14% at 6 to 12 months in distal malignant biliary

obstruction [24–29]. In our study population, we found that

occlusion occurred in only 3/396 (0.8%) cases throughout

our follow-up period of 70 months. In malignancy, we

describe occlusion as a separate event from tumor over-

growth: that is, stent clogging may occur separately from

tumor overgrowth through the stent interstices of the

uncovered portions. It has been hypothesized that tumor

burden may promote the formation of biliary sludge and

debris, thereby leading to occlusion via the accumulation of

these particles rather than tumor spread [26]. In cases of

benign biliary disease, in contrast, adherence of bacteria to

the coating membrane has been thought to result in stent

clogging [8, 30, 31]. Interestingly, all our patients with stent

occlusion resulting from debris had a malignant indication.

We did not find tumor in-growth or tumor extension

through the stent to be a complication. Tumor in-growth

through PCMS is regarded as a failure in the covering

membrane and has been described elsewhere [32]. Overall,

the reduced rates of tumor overgrowth in our study com-

pared to uncovered stents for the treatment of distal

malignant biliary obstruction is consistent with other

established studies [16].

Stricture in the uncovered portion of the PCMS in

benign disease occurred in three cases in our study. This is

less frequent than the study published by Cantu et al. that

cited a higher, late complication rate [25]. That group,

however, included only patients with common bile duct

stricture secondary to chronic pancreatitis, known to be a

more difficult group to treat, and only removed PCMS once

malfunction was observed.

Cholecystitis was the second leading complication in

our study. We report an overall rate of 13/396 (3.3%). Prior

studies have suggested that PCMS may be more likely to

cause cholecystitis than uncovered SEMS, specifically

when the covering material overlaps the orifice of the

Fig. 6 Mucosal hyperplasia at the hilum induced by the uncovered

portion of a previously placed PCMS

520 Dig Dis Sci (2010) 55:516–522

123

cystic duct. This is felt to be due to the decreased perme-

ability of PCMS and obstruction to bile flow, when directly

opposed to the cystic duct [17, 26, 33]. The reported rates

of cholecystitis after PCMS placement are between 2.9%

and 12% [26, 29, 34]. We hypothesize that our relatively

low rate of cholecystitis may be related to our systematic

efforts to avoid covering the cystic duct insertion in benign

diseases and to our attempt to irrigate the gallbladder

during ERCP when it was distended before PCMS place-

ment in malignant diseases [12, 17]. Isayama et al. reported

that cholecystitis occurred mainly in patients with tumor

involving the orifice of the cystic duct in the setting of

unresectable distal biliary malignancy [19]. Occlusion of

the cystic duct by tumor was also found to be the major risk

factor for cholecystitis by Suk et al. [18]. Their study found

that 9/15, or 67%, of patients with cholecystitis had cystic

duct involvement by tumor. Another study used intraductal

ultrasonography to diagnose cystic duct invasion by tumor

and found this to be predictive of cholecystitis [23].

In our study, cholecystitis was found in the setting of

tumor involvement in only 2/13 (15%) cases, despite the

finding that 11/13 (85%) patients who developed chole-

cystitis carried primary diagnoses of malignant biliary

disease. This is quite different from rates cited by other

studies [35]. Indeed, in 8/13 (62%) cases of cholecystitis

we report, the cystic duct was covered by our PCMS,

arguing for the positioning of the PCMS as a more

important risk factor.

On the other hand, since 3/13 (23%) cases of cholecys-

titis (at 20, 47, and 55 days after insertion) occurred while

the stent was placed below the cystic duct, other factors

must play a role, such as bacterial colonization after biliary

sphincterotomy, gallstone disease, or perhaps contrast

injection, as previously suggested in the literature [35–38].

Four patients (1%) developed acute pancreatitis or

worsening pancreatitis after PCMS placement. There were

two patients with chronic pancreatitis, one with ampullary

adenoma, and one with benign biliary stricture. One patient

with chronic pancreatitis developed an infected pseudocyst

4 days after PCMS placement for biliary stricture. The

infected pseudocyst occurred in the setting of the PCMS

covering the PD orifice. This patient required removal of the

PCMS and transpapillary drainage. In the patient with

benign biliary stricture, ERCP revealed poor pancreatic duct

drainage likely contributing to the complication of pancre-

atitis. The patient with ampullary adenoma underwent

ampullary resection with biliary and pancreatic sphincter-

otomy and likely developed post-procedure pancreatitis.

We observed two cases of abdominal pain complicating

PCMS placement, both placed in appropriate position

without obstruction. Our study also revealed one case of

liver abscess and one infected biloma after cholecystec-

tomy in a patient with pancreatic cancer; both required

drainage. We believe neither of these complications was

directly related to the PCMS placement.

The present series of patients with PCMS complications

and their management is the largest reported from a single

center to our knowledge. The efficacy of PCMS must be

weighed against their potential complications and their

specific management. Further improvements in the struc-

ture and composition of PCMS are required to prevent

these complications. Indeed, fully covered stents might be

the best option to decrease tumor overgrowth, but also to

prevent mucosal hyperplasia at the proximal portion of the

SEMS. Fenestration of the covered stent at the level of the

cystic duct insertion might prevent cholecystitis. With

newer covered SEMS offering those options arriving on

the market, further multicenter studies should be per-

formed to determine if better efficacy and lower morbidity

can be achieved in both benign and malignant biliary

diseases.

References

1. Soehendra N, Reynders-Frederix V. Palliative bile duct drain-

age—a new endoscopic method of introducing a transpapillary

drain. Endoscopy. 1980;12(1):8–11.

2. Levy MJ, Baron TH, Gostout CJ, Petersen BT, Farnell MB.

Palliation of malignant extrahepatic biliary obstruction with

plastic versus expandable metal stents: an evidence-based

approach. Clin Gastroenterol and Hepatol. 2004;2(4):273–285.

3. Knyrim K, Wagner HJ, Pausch J, Vakil N. A prospective, ran-

domized, controlled trial of metal stents for malignant obstruction

of the common bile duct. Endoscopy. 1993;25(3):207–212.

4. Prat F, Chapat O, Ducot B, et al. A randomized trial of endo-

scopic drainage methods for inoperable malignant strictures of

the common bile duct. Gastrointest Endosc. 1998;47(1):1–7.

5. Davids PH, Groen AK, Rauws EA, Tytgat GN, Huibregtse K.

Randomised trial of self-expanding metal stents versus polyeth-

ylene stents for distal malignant biliary obstruction. Lancet.1992;340(8834–8835):1488–1492.

6. Arguedas MR, Heudebert GH, Stinnett AA, Wilcox CM. Biliary

stents in malignant obstructive jaundice due to pancreatic carci-

noma: a cost-effectiveness analysis. Am J Gastroenterol.2002;97(4):898–904.

7. Shim CS, Lee YH, Cho YD, et al. Preliminary results of a new

covered biliary metal stent for malignant biliary obstruction.

Endoscopy. 1998;30(4):345–350.

8. Thurnher SA, Lammer J, Thurnher MM, Winkelbauer F, Graf O,

Wildling R. Covered self-expanding transhepatic biliary stents:

clinical pilot study. Cardiovasc Intervent Radiol. 1996;19(1):10–14.

9. Petersen BT. SEMS removal: salvage technique or new para-

digms. Gastrointest Endosc. 2005;62(6):911–913.

10. Kahaleh M, Tokar J, Le T, Yeaton P. Removal of self-expandable

metallic Wallstents. Gastrointest Endosc. 2004;60(4):640–644.

11. Familiari P, Bulajic M, Mutignani M, et al. Endoscopic removal

of malfunctioning biliary self-expandable metallic stents. Gas-trointest Endosc. 2005;62(6):903–910.

12. Kahaleh M, Brock A, Conaway MR, et al. Covered self-

expandable metal stents in pancreatic malignancy regardless of

resectability: a new concept validated by a decision analysis.

Endoscopy. 2007;39(4):319–324.

Dig Dis Sci (2010) 55:516–522 521

123

13. Mullen JT, Lee JH, Gomez HF, et al. Pancreaticoduodenectomy

after placement of endobiliary metal stents. J Gastrointest Surg.

2005;9(8):1094–1105.

14. Carr-Locke DL. Metal stents for distal biliary malignancy: have

we got you covered? Gastrointest Endosc. 2005;61(4):534–536.

15. Wamsteker EJ, Elta GH. Migration of covered biliary self-

expanding metallic stents in two patients with malignant biliary

obstruction. Gastrointest Endosc. 2003;58(5):792–793.

16. Isayama H, Komatsu Y, Tsujino T, et al. A prospective ran-

domised study of ‘‘covered’’ versus ‘‘uncovered’’ diamond stents

for the management of distal malignant biliary obstruction. Gut.2004;53(5):729–734.

17. Kahaleh M, Tokar J, Conaway MR, et al. Efficacy and compli-

cations of covered Wallstents in malignant distal biliary

obstruction. Gastrointest Endosc. 2005;61(4):528–533.

18. Suk KT, Kim HS, Kim JW, et al. Risk factors for cholecystitis

after metal stent placement in malignant biliary obstruction.

Gastrointest Endosc. 2006;64(4):522–529.

19. Isayama H, Kawabe T, Nakai Y, et al. Cholecystitis after metallic

stent placement in patients with malignant distal biliary

obstruction. Clin Gastroenterol Hepatol. 2006;4(9):1148–1153.

20. Baron TH. Expandable metal stents for the treatment of cancer-

ous obstruction of the gastrointestinal tract. N Engl J Med.

2001;344(22):1681–1687.

21. Born P, Neuhaus H, Rosch T, et al. Initial experience with a new,

partially covered Wallstent for malignant biliary obstruction.

Endoscopy. 1996;28(8):699–702.

22. Nakamura T, Hirai R, Kitagawa M, et al. Treatment of common

bile duct obstruction by pancreatic cancer using various stents:

single-center experience. Cardiovasc Intervent Radiol. 2002;25

(5):373–380.

23. Nakai Y, Isayama H, Komatsu Y, et al. Efficacy and safety of the

covered Wallstent in patients with distal malignant biliary

obstruction. Gastrointest Endosc. 2005;62(5):742–748.

24. Isayama H, Komatsu Y, Tsujino T, et al. Polyurethane-covered

metal stent for management of distal malignant biliary obstruc-

tion. Gastrointest Endosc. 2002;55(3):366–370.

25. Cantu P, Hookey LC, Morales A, Le Moine O, Deviere J. The

treatment of patients with symptomatic common bile duct ste-

nosis secondary to chronic pancreatitis using partially covered

metal stents: a pilot study. Endoscopy. 2005;37(8):735–739.

26. Bezzi M, Zolovkins A, Cantisani V, et al. New ePTFE/FEP-

covered stent in the palliative treatment of malignant biliary

obstruction. J Vasc Interv Radiol. 2002;13(6):581–589.

27. Matsushita M, Takakuwa H, Nishio A, Kido M, Shimeno N.

Open-biopsy-forceps technique for endoscopic removal of dis-

tally migrated and impacted biliary metallic stents. GastrointestEndosc. 2003;58(6):924–927.

28. Minami A, Fujita R. A new technique for removal of bile duct

stones with an expandable metallic stent. Gastrointest Endosc.

2003;57(7):945–948.

29. Miyayama S, Matsui O, Terayama N, Tatsu H, Yamamoto T,

Takashima T. Covered gianturco stents for malignant biliary

obstruction: preliminary clinical evaluation. J Vasc Interv Radiol.1997;8(4):641–648.

30. Sung JY, Shaffer EA, Costerton JW. Antibacterial activity of bile

salts against common biliary pathogens Effects of hydrophobicity

of the molecule and in the presence of phospholipids. Dig Dis Sci.1993;38(11):2104–2112.

31. Coene PP, Groen AK, Cheng J, Out MM, Tytgat GN, Huibregtse

K. Clogging of biliary endoprostheses: a new perspective. Gut.1990;31(8):913–917.

32. Rossi P, Bezzi M, Salvatori FM, Panzetti C, Rossi M, Pavia G.

Clinical experience with covered wallstents for biliary malig-

nancies: 23-month follow-up. Cardiovasc Intervent Radiol.1997;20(6):441–447.

33. Schoder M, Rossi P, Uflacker R, et al. Malignant biliary

obstruction: treatment with ePTFE-FEP-covered endoprostheses

initial technical and clinical experiences in a multicenter trial.

Radiology. 2002;225(1):35–42.

34. Hausegger KA, Thurnher S, Bodendorfer G, et al. Treatment ofmalignant biliary obstruction with polyurethane-covered Walls-

tents. AJR Am J Roentgenol. 1998;170(2):403–408.

35. Ainley CC, Williams SJ, Smith AC, Hatfield AR, Russell RC,

Lees WR. Gallbladder sepsis after stent insertion for bile duct

obstruction: management by percutaneous cholecystostomy. Br JSurg. 1991;78(8):961–963.

36. Gregg JA, De Girolami P, Carr-Locke DL. Effects of sphincter-

oplasty and endoscopic sphincterotomy on the bacteriologic

characteristics of the common bile duct. Am J Surg. 1985;149(5):

668–671.

37. Parker HW, Geenen JE, Bjork JT, Stewart ET. A prospective

analysis of fever and bactermia following ERCP. GastrointestEndosc. 1979;25(3):102–103.

38. Deviere J, Motte S, Dumonceau JM, Serruys E, Thys JP, Cremer

M. Septicemia after endoscopic retrograde cholangiopancrea-

tography. Endoscopy. 1990;22(2):72–75.

522 Dig Dis Sci (2010) 55:516–522

123