The modified pancreatic stent system for prevention of post-ERCP pancreatitis: a case-control study

Endoscopic retrograde cholangiopancreatography (ERCP) is the primary method used to manage pancreatobiliary disease, but it is also an invasive procedure that carries significant risks for the patients. The most common complication from the endoscopic sphincterotomy (EST) is acute pancreatitis, and other complications from the procedure include perforations, sepsis and bleeding [1]. Post-ERCP pancreatitis (PEP) is defined as acute abdominal pain within 48 h following ERCP with levels of serum lipase elevated at least 3-fold and a requirement for analgesic drugs for at least 24 h. A systematic survey of 21 prospective studies with 16,855 patients conducted between 1987 and 2003 found a 3.5% occurrence of PEP, 0.4% instances of severe pancreatitis and 0.11% deaths [2].

There are a number of risk factors associated with PEP and they can be divided into either patient-related risk factors or endoscopist-related risk factors. Patient-related risk factors include female gender, previous pancreatitis and Sphincter of Oddi Dysfunction (SOD) [3]. Endoscopist-related risk factors include difficult instrumentation of papilla and pancreatic duct, precut sphincterotomy, endoscopic sphincterotomy, endoscopic pancreatic sphincterotomy (EPT), injection of contrast medium into the pancreatic duct and intraductal ultrasonography [4, 5]. The consequences of these risk factors are various injuries including, mechanical injury, thermal injury, hydrostatic injury, chemical injury, allergic injury, enzymatic injury with intraluminal activation of proteolytic enzymes and infection from contaminated endoscope and accessories.

Despite the introduction of various techniques over several decades to prevent PEP or limit its severity only a few strategies have been proven effective and have been integrated into clinical practice. Several systematic reviews and meta-analyses of randomized, double-blind, clinical trials have examined pancreatic stent placement and the efficacy of drugs, such as diclofenac, somatostatin, and nonsteroidal anti-inflammatory drugs to reduce the incidence of PEP [6–9]. In a meta-analysis of controlled clinical trials involving 481 patients the group that did not have stents implanted had 3-fold higher odds of developing pancreatitis compared with the group of patients that were treated with stents (15.5% vs. 5.8%; Odds Ratio (OR) 3.2: 95% Confidence Interval. Number needed to treat analysis showed that one in every 10 patients could be expected to benefit from pancreatic-duct stent placement [10]. A more recent meta-analysis of 1541 patients found that prophylactic pancreatic stent (PS) placement prevented PEP after ERCP compared with no PS placement thus supporting the importance of PS placement after ERCP for the prevention of PEP [11].

Plastic stents can be divided into three categories including straight PS, single pigtail PS and double pigtail PS. The straight PS and single pigtail PS are commonly used for pancreatic duct drainage. Compared to straight PS single pigtail PS has been demonstrated to minimize stent proximal migration, but there is a higher incidence of spontaneous abscission with single pigtail PS.

The observations made in the previous studies prompted us to design a modified of pancreatic stent system for prevention of PEP. In our system, the PS can be removed along with the nasobiliary catheter. The aim of this observational study was to investigate the feasibility and effectiveness of the modified pancreatic stent system for prevention of post-ERCP pancreatitis.

The positioning of the pancreatic stent (PS) across the ampulla and pancreatic sphincter into the pancreatic duct is presumed to maintain the flow of pancreatic secretions across any flow disruptions caused by injury or edema of these structures. Over the past few decades, substantial evidence has supported that 5-7 cm, 5-Fr diameter, plastic, straight PS seems to be safe, efficacious, and resistant to PEP, especially in high-risk patients [13].

Despite the efficacy there are several complications following stent placement including, stent migration or stent occlusion. Several case reports have detailed rare instances of severe complications. There has been a case report in which the PS migrated into the retroperitoneum posterior to the third part of the duodenum, causing duodenal edema and narrowing [14]. One case reported that a PS migrated into the bile duct causing cholangitis [15]. Another case reported that a PS migrated into the portal vein causing portal vein thrombosis [16]. Finally a case reported perforation of the splenic artery after PS placement in chronic obstructing pancreatitis [17].

More commonly, distal and proximal (upstream) migration of pancreatic duct stents may occur with incidence rates of 7.5% and 5.2%, respectively [18]. If there is no acute pancreatitis after ERCP then spontaneous abscission of the PS is beneficial for the patients since the second ERCP can be avoided. A number of meta-analyses of prospective single-center and multi-center studies have been carried out to identify risk factors for post-ERCP pancreatitis. However, it is unclear why patients with these risk factors are at the highest risk for PEP, and these risk factors do not reliably tell us who will have pancreatitis. In our study, 5 cases of spontaneous PS abscission and 3 cases of acute pancreatitis for pancreatic stent abscission were detected. Fortunately, these patients recovered through drug treatment. If medication is contraindicated with aggravated abdominal pain and continuously rising hematuria amylase, urgent salvage ERCP must be performed to replace the PS [19]. In the modified of pancreatic stent tested in this study, the PS was connected with nasobiliary catheter by a line thus spontaneous abscission of PS will not happen. In our study, one PS was removed after the nasobiliary catheter had migrated distal, however, the distal migration incidence rate of nasobiliary catheter was only 2.1%, which is lower then distal migration of a ordinary PS [20].

A long-term pancreatic stent in pancreas duct can predispose patients to chronic pancreatitis, pancreatolith or pancreatic sepsis. Stent retrieval is important to prevent long-term serious ductal damage, but the removal of proximally migrated stent is technically challenging. Basket or balloon technique is the standard method to retrieve proximally migrated pancreatic stents [21]. The lasso technique can also be used and involves inserting a guide wire through the lumen of the migrated stent followed by insertion of a partially opened polypectomy or gooseneck snare over the wire to grasp the stent [22, 23]. Rat-tooth forceps can also used but a small pancreatic duct can preclude full opening of the forceps. Additionally, when the tip of the stent impacts the duct the rat-tooth forceps technique may not be successful. Instead a grasping tripod removal of the stent has been reported to be helpful [24]. There have only been two previous reports on the use of SpyGlass pancreatoscopy to remove migrated pancreatic duct stents. SpyGlass pancreatoscopy facilitates successful guide wire cannulation of migrated stents, which can then be removed with a Soehendra Stent Retriever [25]. We had reported 7 cases of proximally migrated PS with the incidence rates of 2.9%, and these proximally migrated stents were successfully removed by basket and balloon [26]. In the modified pancreatic stent system, proximal migration of PS will be avoided by using a line that is linked with a nasobiliary catheter.

Many endoscopists are trying to get away from the habit of routinely inserted nasobiliary drains, since nasobiliary drain can increase the procedure time and patients’ discomfort, while biliary drainage by nasobiliary drain and drainage by stent are equally safe and effective treatments for acute cholangitis [27–29]. A second endoscopy is needed to remove the biliary stent, which will also increase patient’s discomfort and costs. In China, a nasobiliary catheter placement is recommended after ERCP procedure, since ENBD not only significantly reduces the incidence of hyperamylasemia and pancreatitis but also decreases the length of hospital stay in patients with EST, EPBD and repeated stone extraction [30, 31]. Compared with 6-Fr nasobiliary catheter, the 4-Fr nasobiliary catheter is useful to reduce nasal discomfort [32].

Currently, a PS is mostly occluded as early as 1 month after insertion [33], A follow-up procedure to remove the stent is generally recommended within 1–2 weeks following surgery to avoid the complication of stent occlusion or inward stent migration [34]. A meta-analysis showed that prophylactic pancreatic stents made the probability of pancreatitis dropped to 1.3%, therefore, 98.7% PS could be removed in a week [35]. With the modified pancreatic stent system, a second endoscopy can be avoided because the PS will be removed along with the nasobiliary catheter. The new system greatly reduces the pain of the patients and the costs associated with follow-up procedures. If the line of nasobiliary catheter in type one of the modified pancreatic stent system is released and a guide line is input into the nasobiliary catheter, the loop at the head of the nasobiliary catheter will become straight. Then, the nasobiliary catheter can be removed with the PS remaining in pancreatic duct. In type one of the modified pancreatic stent system this can be achieved if the line is removed.

In summary, this study investigated the feasibility and effectiveness of a modified pancreatic stent system for prevention of post-ERCP pancreatitis. Our analysis indicated that the modified pancreatic stent system had the same effect of preventing post-ERCP pancreatitis, no obvious difficulty of stent placement, lower rate of stents proximal migration and spontaneous abscission, and the advantage of easier removed compared with ordinary pancreatic stent. Therefore this modified pancreatic stent system could be considered as a complementary medical approach for prevention of post-ERCP pancreatitis. However, these conclusions must be verified by a long-term evaluation study with a larger sample size.