Pancreatic Stents

Use of stents in the pancreas has been confined and limited to referral centers that specialize in the treatment of patients with severe pancreatitis and acute relapsing pancreatitis. With therapeutic development in endoscopic treatment of pancreatic diseases and a better understanding of the cause and prevention of ERCP related complications, the use of stents has been extended to transmural drainage of pancreatic fluid collection or of pancreatic ducts has well as to prophylaxis of post-ERCP pancreatitis. As a result, indication for pancreatic stenting and the kind of stents to be used as well as the followup after placement varies. This article reviews the major indication for pancreatic stent placement and focuses on the choice of stent, technique of implantation and followup.

Although there are various types of stents that provide drainage and bypass for the treatment of bile duct obstruction, leaks, and stones, their use in the pancreas has for long been confined and limited to referral centers that specialize in the treatment of patients with severe chronic pancreatitis (CP) and acute relapsing pancreatitis.

Therapeutic developments in endoscopic treatment of pancreatic diseases and a better understanding of the cause and prevention of endoscopic retrograde cholangiopancreatography (ERCP)–related complications have recently expanded the use of stents placed into the pancreatic duct and directly into pancreatic fluid collections (PFCs).

There are now a variety of indications for pancreatic stent placement, although some are still debated, whereas others are becoming scientifically established. Nearly all pancreatic stents are composed of plastic and inserted into the pancreatic duct. Their size, shape, and purpose vary by indication, and follow-up after placement must be tailored to the indication.

Also unique to pancreatic stents is that they are almost exclusively used for the treatment and/or prevention of benign conditions despite data to support their role in palliation of pain in selected patients with pancreatic cancer.

This article reviews the major indications for pancreatic stent placement and focuses on the choice of stents, technique of implantation, and follow-up.

Prevention of post-ERCP pancreatitis

Pancreatitis remains the most common complication of ERCP and occurs after 1% to 25% of procedures. Large prospective studies have shown that its incidence varies with the type and indication of the procedure performed, patient susceptibility, and case volume of the operator. The severity of post-ERCP pancreatitis (PEP) is much more difficult to predict. Severe PEP accounts for around 10% of all cases, and although risk factors for PEP have been identified, predictors of severe PEP are lacking. With the exception of nonsteroidal antiinflammatory drugs (100 mg of diclofenac or indomethacin administered rectally), no other drug prophylaxis of PEP pancreatitis has been proven to be effective.

Over the last 20 years, there have been major advances in the ERCP technique to prevent PEP. These include guidewire-directed deep biliary cannulation and, more importantly, placement of prophylactic pancreatic duct stents in patients at a high risk for developing PEP.

A total of 8 randomized controlled trials (RCTs), multiple prospective uncontrolled studies, and 4 meta-analysis have compared the rates of pancreatitis after ERCP with and without prophylactic pancreatic stent placement. Prophylactic stent placement not only reduces the incidence of PEP, particularly in high-risk patients, but also virtually eliminates severe pancreatitis.

Many studies criticize the absence of intent-to-treat analysis (patients with attempted but unsuccessful stent placement were excluded). However, a meta-analysis of the 4 RCTs used intent-to-treat principles by assuming that PEP developed in patients in whom attempted prophylactic pancreatic stent placement failed, even when the clinical outcome was not stated in the original study. Despite using this approach, the odds ratio in the stent group was 0.44 compared with controls and was significantly different in favor of stent placement. On the basis of these results, prophylactic stent placement can be considered as the single most-important advance in the last 15 years for prevention of PEP in high-risk patients.

Despite these findings, questions remain as to when to place a prophylactic pancreatic stent, what type of stent to place, and what is the optimal follow-up period to ensure adequate removal.

The incidence of adverse events associated with pancreatic stent placement is around 4% and must be considered in the decision-making process for placement of stent. Immediate complications include the potential for the guidewire to damage secondary pancreatic duct branches, possible misplacement completely into the duct, ductal perforation by the stent, or trauma caused by multiple manipulations during attempted placement. Midterm complications include stent-induced ductal alterations causing CP-like changes, which although usually regress spontaneously, can lead to permanent damage, especially when placed in normal ducts for a prolonged period. For these reasons, traditional 5F and 7F flanged stents made of rigid polyethylene are not recommended because they (1) may induce ductal changes and (2) do not spontaneously pass out of the duct because of the presence of a proximal flap. The most frequently used stents are short, 4F to 5F in diameter, and devoid of proximal flaps (Cook Endoscopy, Winston Salem, NC, USA; Hobbs Medical Inc, Stafford Spring, CT, USA), and because they are made of newer materials they are potentially safer than the traditional polyethylene stents. Several investigators have proposed the use of long, unflanged 3F pancreatic stents that require the use of a 0.018-in guidewire. Although there is less early migration out of the duct (potentially decreasing the rate of PEP) and the procedure may be less traumatic to the duct, the additional guidewire exchange from a 0.035-in wire used for other aspects of the procedure are time consuming and can cause ductal injury. In addition, the need for negotiating tight loops in the pancreatic neck renders their placement more difficult. Two recent RCTs that compared short 5F stents with long 3F stents for the prevention of PEP did not show significant differences in PEP with the use of the 2 stents but showed that there was less spontaneous migration at 2 weeks and there were more failures of implantation when using the 3F stents. At present, 3- to 5-cm long 5F stents without internal flanges, with an external (duodenal) pigtail or flap, are considered to be the best choice. Stent passage out of the duct (preferred to prevent the need for an additional endoscopic procedure) occurs by 2 weeks in more than 95% of the cases. A plain abdominal radiograph is necessary at that time, and the stent should be removed endoscopically if it remains ( Fig. 1 ).