Small prophylactic pancreatic duct stents: an assessment of spontaneous passage and stent-induced ductal abnormalities

• Introduction
• Patients and methods
• Results
• ERCP indications and findings
• Spontaneous passage of stents
• Evaluation of ductal changes
• Discussion
• References

Background and study aims: Placing small stents in the pancreatic duct at endoscopic retrograde cholangiopancreatography reduces the risk of pancreatitis. However, this practice means that a second procedure might be required to remove the stent, and stents can also damage the duct. The aims of this study were to determine the frequency of spontaneous dislodgment and to assess the incidence of stent-induced ductal irregularities.

Patients and methods: We performed a retrospective analysis of consecutive patients seen over a 3-year period (2001 - 2004) who had undergone placement of a 3-Fr pancreatic duct stent and in whom the fate of the stent had been documented. Radiographs were reviewed to determine stent passage at 30 days. If applicable, follow-up pancreatograms were reviewed to assess for stent-induced ductal abnormalities. Statistical analysis was performed using chi-squared and Fisher’s exact tests for proportions, and 95 % binomial confidence intervals (CI) were calculated.

Results: Records for 125 consecutive patients who had had 3-Fr pancreatic stents placed were reviewed. The stents had passed spontaneously within 30 days in 110/125 patients (88 %). In the remaining 15 patients (12 %, 95 % CI 6.9 % - 19 %), the stents were still present on follow-up radiographs after a median time of 36 days, (range 31 - 116 days). Stent length, pancreatic sphincterotomy, and pancreas divisum had no effect on the likelihood of spontaneous passage. No stent-induced ductal irregularities were observed.

Conclusions: Nearly 90 % of prophylactic 3-Fr pancreatic duct stents pass spontaneously within 30 days, and these stents were not observed to induce changes in the pancreatic duct.

Introduction

Endoscopic retrograde cholangiopancreatography (ERCP) causes pancreatitis in approximately 5 % of individuals [1]. The risk is increased in younger patients, in women, and when sphincter dysfunction is suspected, and with the use of certain techniques (precut access, multiple pancreatic duct injections). Several studies have shown that the incidence of pancreatitis in high-risk patients can be reduced by the prophylactic placement of a small pancreatic duct stent [2] [3] [4] [5]. However, stenting of the pancreatic duct has been shown to cause ductal irregularities, both in canine models and in humans [6] [7].

Small-caliber (3 - 5-Fr) pancreatic duct stents have become increasingly popular because they pass spontaneously and are soft and pliable. Both of these factors are thought to minimize the risk of duct injury. However, even the smallest stents (3 Fr) were associated with pancreatic ductal irregularities in the only study that has been published on this subject [8]. We have used 3-Fr stents as prophylaxis against pancreatitis in all high-risk patients (patients undergoing access papillotomy or pancreatic manometry, patients with suspected sphincter of Oddi dysfunction, and patients undergoing pancreatic sphincterotomy) since 2001. The aim of this study was to determine the frequency of spontaneous dislodgment of these stents and to identify stent-induced irregularities of the pancreatic duct.

Patients and methods

We undertook a retrospective analysis of consecutive patients who had undergone a 3-Fr pancreatic duct stent placement between 2001 and 2004, in whom the fate of the stent had been documented, using the Medical University of South Carolina endoscopy database (GI-Trac, Akron Systems Development). A total of 3999 ERCPs were performed at our center over this period.

Radiographs, or the reports if the films were not accessible, were reviewed to assess stent passage. Stent persistence was defined as identification of the stent in the region of the pancreatic head more than 30 days after placement. In order to identify ductal changes, the database was searched to identify patients who had a follow-up ERCP after initial 3-Fr stent placement at our center. The pairs of pancreatograms were compared by one of three biliary endoscopists in a blinded manner.

Statistical analysis was performed using chi-squared and Fischer’s exact tests for proportions, and 95 % binomial confidence intervals (CI) were calculated. Complications were defined by accepted criteria [9]. The study was approved by the Institutional Review Board of the Medical University of South Carolina.

Results

The stents we used (Cook GI Endoscopy, Winston-Salem, North Carolina, USA) have a single duodenal pigtail, no internal flanges, and were placed over an 0.018-inch-diameter guide wire ([Fig. 1]). Stent length was determined by the contour of the pancreatic duct. Ideally, we preferred that the inner tip of the stent was left in a straight portion of the main pancreatic duct, beyond the genu. Shorter stents were used occasionally where the anatomy was difficult. Some of the patients underwent pancreatic sphincterotomy using pull-type or needle-knife techniques for pancreatic sphincter hypertension or pancreas divisum. Sphincterotomy was never necessary for stent placement.

Patients were instructed to have an abdominal radiograph (to include the diaphragms) within 3 - 4 weeks after the procedure. Stents remaining after that time were removed endoscopically.

ERCP indications and findings

We reviewed the records of 125 consecutive patients who had had 3-Fr pancreatic stents placed ([Table 1]). The median stent length was 12 cm (range 5 - 12 cm). ERCP was indicated on the basis of suspected sphincter of Oddi dysfunction in 58 patients (46 %) [10] [11]; another 43 patients (34 %) underwent ERCP in order to make a diagnosis of pancreatitis (defined as typical pain, with amylase or lipase levels three times normal levels or more, and including new-onset or acute, recurrent pancreatitis). Pancreatic sphincterotomy was performed in 70 patients (56 %) during the same procedure as the pancreatic stent placement.

Pancreatic duct stents were indicated following manometry (86 % patients), vigorous pancreatic manipulation/access papillotomy (9 %), or pancreatic sphincterotomy without manometry (4 %), and in patients with a history of post-ERCP pancreatitis (1 %). A total of 84 patients underwent pancreatic manometry, and 50 of these patients (60 %) were found to have pancreatic sphincter hypertension; 53 patients underwent biliary manometry, 25 of whom (47 %) were found to have biliary sphincter hypertension.

Pancreatography at initial ERCP was normal in 105/125 patients (84 %); 20/125 patients (16 %) showed morphologic changes of mild chronic pancreatitis, based on standard criteria [12]. Nine patients (7 %) had pancreas divisum.

Spontaneous passage of stents

Spontaneous passage of the stent was observed in 110/125 patients (88 %) within 30 days (median 22 days, range 2 - 30 days) after placement. Stent persistence was documented in 15 patients (12 %, 95 % CI 6.9 % - 19 %) who were noncompliant with the request to have a radiograph taken. Imaging in these 15 patients was performed a median of 36 days (31 - 116 days) after stent placement.

The likelihood of stent retention was not significantly associated with concurrent pancreatic sphincterotomy, treatment of pancreas divisum, abnormal initial pancreatogram, or stent length ([Table 1]). Four patients had two 3-Fr stents placed simultaneously; they all passed spontaneously at day 13, 22, 26, and 28. One patient with Billroth II anatomy passed their stent within 18 days.

Pancreatic-type complications were observed in 7/125 patients (5.6 %) after ERCP: pancreatitis occurred in five patients, and unexplained pain and pyrexia occurred in two patients, all episodes were graded as mild. These seven patients were shown to have passed their stents by day 13, 14, 16, 21, 22, 24, and 116.

Evaluation of ductal changes

Second pancreatograms were available for 43/125 patients (34 %; 42 endoscopic retrograde pancreatograms and one magnetic resonance pancreatogram). The indication for follow-up was recurrent or persistent symptoms in all cases. Seven of these patients came from the persistent stent group, although a persistent stent was never the sole indication for a second ERCP. Repeat imaging was performed after a median interval of 144.5 days (range 7 - 515 days) ([Fig. 2], [3]).

Five patients (12 %) in this group had mild chronic pancreatitis (with a normal main pancreatic duct) on the index ERCP; the remainder had a normal pancreatogram. No new duct changes were detected in any of the 43 patients.

Discussion

Prophylactic stenting of the pancreatic orifice has become increasingly popular in referral centers. It has been shown to reduce the frequency of post-ERCP pancreatitis, especially in high-risk groups such as patients with suspected sphincter of Oddi dysfunction, and has dramatically reduced the incidence of severe post-ERCP pancreatitis [2] [3] [4] [13] [14]. Data from this study support this finding, with a rate of pancreatitis of only 4 % (all graded as mild), despite the preponderance of high-risk cases included in the study. The use of stents without internal anchoring flaps is also advantageous because most pass spontaneously, obviating the need for another endoscopy to remove them. Radiographs showed that 88 % of the stents had passed within 30 days, a similar figure to that reported in other centers. The likelihood of stent passage was not affected by the presence of pancreatic pathology or pancreas divisum, stent length, or the performance of pancreatic sphincterotomy, so these factors are unlikely to help guide the selective utilization of radiography to follow the course of the stents after ERCP.

Enthusiasm for prophylactic stenting is tempered by two concerns. Firstly, stent placement is sometimes technically difficult due to tortuosity of the duct, and prolonged attempts to place a stent could prove to be counterproductive. Even at expert centers, failure to place a stent can occur in up to 10 % of cases, and a recent study by Freeman et al. [15] reported that failure resulted in nearly two-thirds of the cases of post-ERCP pancreatitis being moderate or severe [2] [3] [15] [16]. Secondly, there is the possibility of stent-induced damage to the duct and parenchyma. This is a well-recognized complication when larger-diameter stents (5 - 7 Fr) are used in the pancreas, both in dogs and in humans [6] [7] [17] [18] [19]. One study reported that 80 % of patients showed morphologic changes of the pancreatic duct when stents were removed [17]. Although most changes were classed as minor (defined as less than 20 % luminal narrowing) [17], more severe and irreversible changes have been demonstrated which have led to the need for resective surgery [20].

We observed no stent-related duct changes in the 43 patients who had a second pancreatogram; 38/43 of these patients (88 %) had a normal index ERCP. This differs from the observations made in the study by Rashdan et al. [8], in which 13 % of patients who had 3-Fr stents placed developed duct abnormalities; only 74 % of their patients began with a normal pancreatogram. One could postulate that the normal pancreatic duct stands to benefit the most from 3-Fr stents. Indeed, Rashdan et al. found a greater risk of stent-induced changes in the group with normal ductography at baseline. Because the median interval between stent placement and the second pancreatogram in our study was over 4 months, however, it is possible that ductal irregularities could have occurred but resolved. In support of this theory, Rashdan et al. found duct changes less frequently in their group of patients who had a delayed pancreatogram.

The limitations of our study are those inherent in any retrospective study. It is certainly possible that we had a proportionally longer follow-up of the patients with the problematic stents than in patients whose stents passed spontaneously. In this context, the spontaneous passage rate is likely to have been underestimated. Defining spontaneous passage as passage by day 30 is admittedly arbitrary; the design of the study did not permit us to determine exactly when the stent passed from the pancreas. In fact, 11 patients passed their stent in 10 days or less. The results should be generalizable with respect to the effectiveness in preventing post-ERCP pancreatitis, the minimal adverse ductal effects, and the high rate of spontaneous dislodgment.

Small-caliber pancreatic duct stents (specifically, 3-Fr stents in our study) are an appealing option for prophylaxis against post-ERCP pancreatitis. The high spontaneous passage rate previously demonstrated by others was confirmed in our study. In addition, no long-term deleterious effects on the pancreatic duct were observed despite placing mostly longer stents (> 8 cm) around the genu. In conclusion, 3-Fr stents seem to be preferable to larger-caliber stents on the basis of their spontaneous passage and their benign effects on pancreatic duct morphology, while offering equal effectiveness in the prevention of post-ERCP pancreatitis.

Competing interests: None

References

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  Search in Google Scholar
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C. Lawrence, MD

Digestive Disease Center

Medical University of South Carolina

96 Jonathan Lucas Street, Suite 210

POB 250327

Charleston

South Carolina 29425

USA

Fax: +1-843-792-1707

Email: Lawrench@musc.edu

References

• 1 Freeman M L, Nelson D B, Sherman S. et al . Complications of endoscopic biliary sphincterotomy.  N Engl J Med. 1996;  335 909-918
  CrossrefPubMedSearch in Google Scholar
• 2 Fazel A, Quadri A, Catalano M F. et al . Does a pancreatic duct stent prevent post-ERCP pancreatitis? A prospective randomized study.  Gastrointest Endosc. 2003;  57 291-294
  CrossrefPubMedSearch in Google Scholar
• 3 Tarnasky P R, Palesch Y Y, Cunningham J T. et al . Pancreatic stenting prevents pancreatitis after biliary sphincterotomy in patients with sphincter of Oddi dysfunction.  Gastroenterology. 1998;  115 1518-1524
  PubMedSearch in Google Scholar
• 4 Fogel E L, Eversman D, Jamidar P. et al . Sphincter of Oddi dysfunction: pancreaticobiliary sphincterotomy with pancreatic stent placement has a lower rate of pancreatitis than biliary sphincterotomy alone.  Endoscopy. 2002;  34 280-285
  Thieme ConnectPubMedSearch in Google Scholar
• 5 Singh P, Das A, Isenberg G. et al . Does prophylactic pancreatic stent placement reduce the risk of post-ERCP acute pancreatitis? A meta-analysis of controlled trials.  Gastrointest Endosc. 2004;  60 544-550
  CrossrefPubMedSearch in Google Scholar
• 6 Sherman S, Alvarez C, Robert M. et al . Polyethylene pancreatic duct stent-induced changes in the normal dog pancreas.  Gastrointest Endosc. 1993;  39 658-664
  CrossrefPubMedSearch in Google Scholar
• 7 Kozarek R A. Pancreatic stents can induce ductal changes consistent with chronic pancreatitis.  Gastrointest Endosc. 1990;  36 93-95
  CrossrefPubMedSearch in Google Scholar
• 8 Rashdan A, Fogel E L, McHenry Jr L. et al . Improved stent characteristics for prophylaxis of post-ERCP pancreatitis.  Clin Gastroenterol Hepatol. 2004;  2 322-329
  CrossrefPubMedSearch in Google Scholar
• 9 Cotton P B, Lehman G, Vennes J. et al . Endoscopic sphincterotomy complications and their management: an attempt at consensus.  Gastrointest Endosc. 1991;  37 383-393
  CrossrefPubMedSearch in Google Scholar
• 10 Corazziari E, Shaffer E A, Hogan W J. et al . Functional disorders of the biliary tract and pancreas.  Gut. 1999;  45 (Suppl 2) II48-II54
  PubMedSearch in Google Scholar
• 11 Hogan W J, Geenen J E. Biliary dyskinesia.  Endoscopy. 1988;  20 (Suppl 1) 179-183
  PubMedSearch in Google Scholar
• 12 Axon A T, Classen M, Cotton P B. et al . Pancreatography in chronic pancreatitis: international definitions.  Gut. 1984;  25 1107-1112
  CrossrefPubMedSearch in Google Scholar
• 13 Freeman M L, Guda N M. Prevention of post-ERCP pancreatitis: a comprehensive review.  Gastrointest Endosc. 2004;  59 845-864
  CrossrefPubMedSearch in Google Scholar
• 14 Freeman M L. Role of pancreatic stents in prevention of post-ERCP pancreatitis.  JOP. 2004;  5 322-327
  PubMedSearch in Google Scholar
• 15 Freeman M L, Overby C, Qi D. Pancreatic stent insertion: consequences of failure and results of a modified technique to maximize success.  Gastrointest Endosc. 2004;  59 8-14
  CrossrefPubMedSearch in Google Scholar
• 16 Smithline A, Silverman W, Rogers D. et al . Effect of prophylactic main pancreatic duct stenting on the incidence of biliary endoscopic sphincterotomy-induced pancreatitis in high-risk patients.  Gastrointest Endosc. 1993;  39 652-657
  CrossrefPubMedSearch in Google Scholar
• 17 Smith M T, Sherman S, Ikenberry S O. et al . Alterations in pancreatic ductal morphology following polyethylene pancreatic stent therapy.  Gastrointest Endosc. 1996;  44 268-275
  Search in Google Scholar
• 18 Sherman S, Hawes R H, Savides T J. et al . Stent-induced pancreatic ductal and parenchymal changes: correlation of endoscopic ultrasound with ERCP.  Gastrointest Endosc. 1996;  44 276-282
  CrossrefPubMedSearch in Google Scholar
• 19 Siegel J, Veerappan A. Endoscopic management of pancreatic disorders: potential risks of pancreatic prostheses.  Endoscopy. 1991;  23 177-180
  Thieme ConnectPubMedSearch in Google Scholar
• 20 Alvarez C, Robert M, Sherman S, Reber H A. Histologic changes after stenting of the pancreatic duct.  Arch Surg. 1994;  129 765-768
  PubMedSearch in Google Scholar

C. Lawrence, MD

Digestive Disease Center

Medical University of South Carolina

96 Jonathan Lucas Street, Suite 210

POB 250327

Charleston

South Carolina 29425

USA

Fax: +1-843-792-1707

Email: Lawrench@musc.edu