Endoscopic Therapy of Chronic Pancreatitis

Transcription

1 AMERICAN SOCIETY FOR GASTROINTESTINAL ENDOSCOPY Endoscopic Therapy of Chronic Pancreatitis Chronic pancreatitis is an inflammatory process characterized by destruction of pancreatic parenchyma and ductal structures with formation of fibrosis. Pain is the predominant symptom of chronic pancreatitis and its origin appears to be multifactorial. 1-4 The multiplicity of causes of pain helps explain the mixed results achieved by current methods of therapy. Most therapeutic efforts in the treatment of chronic pancreatitis are directed toward control of symptoms. Medical therapies (dietary alterations, analgesics, nerve blocks, oral enzyme supplements, octreotide) are variably effective in relieving pain, 1 leaving surgical therapy as the main therapeutic option for patients who fail to improve with medical management. Early postoperative pain relief is seen in 80-90% of patients; however, pain recurs in 20-50% during long-term followup. 5,6 Surgical drainage procedures are associated with a morbidity rate of 20-40% and an average mortality rate of 4%. 3 While endoscopic therapy has revolutionized the approach to a variety of biliary tract disorders, it is only recently that the indications for therapeutic endoscopy have been expanded to include disorders of the pancreas Although the endoscopic approach has not been compared directly to surgery, endoscopic drainage is appealing in that it may offer an alternative to surgical drainage procedures with generally less morbidity and mortality. Furthermore, endoscopic procedures do not preclude subsequent surgery, if necessary. Moreover, the outcome from reducing the intraductal pressure by endoscopic methods may be a predictor for the success of surgical drainage. 12 In chronic pancreatitis, there are certain pathologic alterations of the pancreatic duct, bile duct or sphincters that lend themselves to endoscopic therapy. In general, the aim of endoscopic therapy is to alleviate outflow obstruction of the pancreatic duct. This presumes that ductal hypertension is the cause for the patient s symptoms. In the setting of chronic pancreatitis, ERCP is utilized to treat pancreatic strictures, pancreatic ductal stones, bile duct strictures, and pseudocysts. Outcome data following endoscopic therapy in chronic pancreatitis are rapidly accumulating. The data, however, are often difficult to interpret because of the heterogeneous populations treated and because of the multiple therapies performed in a given patient. To date, no randomized controlled trials comparing endoscopic therapy to medical and/or surgical therapy have been reported. Thus, in most settings, there are no firm data as to when and if endoscopic intervention is appropriate. Because of the complexity of the techniques, high rate of complications, and absence of definitive data supporting the role of ERCP in chronic pancreatitis, endoscopic interventions should, in general, be limited to tertiary care centers staffed by experienced endoscopists. In this guideline, the current state-of-the-art endoscopic treatment of chronic pancreatitis will be reviewed. PANCREATIC DUCTAL STRICTURES Benign strictures of the main pancreatic duct are generally due to inflammation or necrosis around the main pancreatic duct. Given the putative role of ductal hypertension in the genesis of symptoms (at least in a subpopulation of patients), the utility of pancreatic duct stents for the treatment of dominant pancreatic duct strictures is being evaluated In experimental models, pancreatic duct stents have been shown to reduce elevated ductal pressures significantly, though not as effectively as surgical measures. 22 The best candidates for stenting appear to be those patients with a stricture in the pancreatic head and upstream dilation. 13 The technique for placing a stent in the pancreatic duct is similar to that used for placing a biliary stent. In most patients, a pancreatic sphincterotomy (with or without a biliary sphincterotomy) via the major or minor papilla is performed to facilitate placement of accessories and stents. A guidewire must be maneuvered upstream to the narrowing. High-grade strictures require dilation prior to insertion of the endoprosthesis. This may be performed with graduated dilating catheters or hydrostatic balloon dilating catheters. In general, the diameter of the stent should not exceed the downstream duct diameter. The outcome of pancreatic duct stent placement (usually with ancillary procedures) has been evaluated at several tertiary centers In 7 selected series totaling 328 patients, successful stent placement was achieved in 82 to 100% of patients. Sixtysix percent of patients in whom a stent was placed successfully were reported to benefit from therapy during a mean follow-up of 8 to 39 months. The VOLUME 52, NO. 6, 2000 GASTROINTESTINAL ENDOSCOPY 843

2 Author Title major complication and mortality rates associated with this therapy were 19% and 1%, respectively. In one study, the predictors of a long-term benefit were resolution of the stricture and reduction in the pancreatic duct diameter by at least 2 mm. 20 Although not clarified in several studies, it appears that many patients still had a stent in place during the followup interval. Two institutions 19,20 have reported that symptomatic improvement may persist after pancreatic stent removal despite persistence of the stricture. Although these data suggest that resolution of the stricture is not a prerequisite for symptomatic improvement, other factors may account for symptomatic improvement, including other therapies performed at the time of stent placement (e.g., pancreatic sphincterotomy, pancreatic stone removal), improved luminal patency, and the tendency of the pain of chronic pancreatitis to decrease with time, often with resolution as marked deterioration of pancreas function occurs. 23 Only randomized controlled studies comparing endoscopic, surgical, and medical management will allow determination of the true long-term efficacy of stent placement for pancreatic strictures. Unanswered questions include: Which patients are the best candidates for stent placement?; Is upstream dilation a prerequisite?; Does the response to stent placement depend on the etiology of chronic pancreatitis? At present, stent placement for pancreatic duct strictures in chronic pancreatitis is still considered to be investigational in most settings. Complications related directly to the stent include occlusion which may result in pain and/or pancreatitis, migration into or out of the duct, duodenal erosions, pancreatic infection, ductal perforation, stone formation and ductal and parenchymal changes. 10 The latter changes (which may simulate chronic pancreatitis) are, perhaps, the most concerning in patients with a previously normal pancreas. In contrast, such ductal and parenchymal damage may be inconsequential in patients with advanced chronic pancreatitis. PANCREATIC DUCTAL STONES Alcohol-induced, tropical, and idiopathic pancreatitis are the main categories of chronic calcifying pancreatitis. There is debate as to whether pancreatic calculi aggravate the clinical course of chronic pancreatitis (manifested as increased abdominal pain or recurrent attacks of acute pancreatitis) or are merely the inevitable sequelae of ongoing gland destruction. The rationale for intervention is based on the premise that pancreatic stones increase the intraductal pressure (and probably the parenchymal pressure, with resultant pancreatic ischemia and pain) upstream of the obstructed focus. Reports indicating that endoscopic or surgical removal of pancreatic calculi results in improvement of symptoms support this notion. 12 Moreover, stone impaction may cause further trauma to the pancreatic duct with epithelial destruction and stricture formation. 24,25 Thus, identification of main pancreatic ductal stones in a symptomatic patient warrants consideration of removal. A pancreatic sphincterotomy is usually performed to facilitate access to the pancreatic duct prior to attempts at stone removal. The need for a simultaneous biliary sphincterotomy has not been clarified, although it appears not to be necessary in most cases. Downstream strictures usually require dilation. Standard biliary stone retrieval devices (baskets and balloons) are the most common accessories used to remove pancreatic duct stones. In series of highly selected patients in whom endoscopic techniques alone were used, complete stone clearance was achieved in 93 of 147 patients 63%. The major complication rate was 9% (primarily pancreatitis) and the mortality rate was 0%. During follow-up periods of months, symptoms improved in 74% of patients. Large or impacted stones and stones upstream of a stricture may require a lithotripsy technique to fragment the stones and facilitate endoscopic removal. Extracorporeal shockwave lithotripsy (ESWL) is the most commonly used adjunctive endoscopic technique. The availability of ESWL has expanded the patient population treated by endoscopic techniques. In 7 selected ESWL series involving 260 patients (33-39), complete stone clearance was achieved in 59% of patients with a major complication rate of 19% (primarily resulting from the endoscopic procedure) and mortality rate of 0%. During a mean follow-up interval of 18 months, 72% of patients were reported to be improved. Stone dissolution via ductal irrigation (contact dissolution) or an oral agent is an attractive endoscopic adjunct for stone removal. Intraduodenal or intraductal infusion of citrate may be effective. 24,40,41 At the present time, however, no rapidly effective solvent for human use is available to treat pancreatic stones. Further trials are needed to establish a role for medical therapy (either alone or as an aid to endoscopic measures) in treating patients with symptomatic pancreatic duct stones. In summary, it appears that removal of pancreatic duct stones may result in symptomatic benefit. Longer periods of follow-up will be necessary to determine the stone recurrence rate and whether 844 GASTROINTESTINAL ENDOSCOPY VOLUME 52, NO. 6, 2000

3 Title Author endoscopic success results in long-standing clinical improvement or permanent regression of the morphological changes. The currently available data suggest that the clinical outcome after successful endoscopic removal is similar to surgical outcome with lower morbidity and mortality rates. 10 However, controlled trials comparing these techniques with medical therapy will be needed to determine the role of endoscopy in this setting. Pancreatic Pseudocysts Pancreatic pseudocysts may complicate the course of chronic pancreatitis in 20 to 40% of cases. 42,43 Traditionally, surgery has been the treatment of choice for such patients. The introduction of ultrasound and CT-guided needle and catheter drainage techniques provided a non-operative alternative to managing patients with pseudocysts. More recently, an endoscopic approach has been applied. The decision to drain a pseudocyst should be made independent of the intervention chosen, that is, before the therapy is chosen, an indication to drain the pseudocyst should be established. Although the first endoscopic transmural drainage was described in 1975, endoscopic therapy of pseudocysts has only recently gained popularity. Two endoscopic approaches (transmural and transpapillary) can be utilized to treat pseudocysts. 44 The choice of therapy is in part dependent on whether the cyst communicates with the pancreatic duct or is in close apposition to the gut lumen. The aim of endoscopic transmural drainage is to create a communication between the pseudocyst cavity and the bowel lumen (cystogastrostomy or cystoduodenostomy), allowing for internal drainage of the fluid collection. Two prerequisites should be met before this treatment is attempted: 1) a well-defined visible extrinsic impression on the gastric or duodenal wall should be evident, and 2) the distance between the cyst and the gut lumen should not exceed 1 cm. 44 Many authorities advocate needle localization of the cyst through the gastric or duodenal wall to identify a safe site before diathermic puncture is performed. 45 Diathermic needle cautery is then used to create a fistula between the gut lumen and the cyst. A guidewire is then deeply looped into the pseudocyst cavity. Most authorities recommend dilating the tract with an 8-10 mm balloon. One or more double pigtail stents are then placed in the tract. When the fluid contains debris or obvious necrotic material, a nasocystic catheter should be placed for lavage. 46 The transpapillary route for pseudocyst drainage is preferred when transmural drainage is not feasible and a duct-to-cyst communication is present. As compared to the transmural approach, this technique has a lower risk of bleeding and perforation but may have a higher rate of infection, especially if the cyst contains debris. 44 In this technique, a guidewire is advanced into the pseudocyst or across the leak site into the upstream duct. Biliary and pancreatic sphincterotomies are commonly done but are not mandatory. A pancreatic stent is then placed either into the cyst or the upstream duct using the same principles and techniques used for placement of a stent. The size, length, and shape of the endoprosthesis should be adapted to the anatomy and diameter of the duct. It is important to address associated pancreatic ductal disease such as stones or strictures. Failure to treat these associated pancreatic ductal diseases may result in recurrence of the pseudocyst. Followup CT or ultrasound is recommended at approximately monthly intervals until the cyst resolves completely and the stent can be removed. More than 400 cases of endoscopically managed pseudocysts have been reported The results indicate that endoscopic therapy is associated with a high technical success rate (80-95%), acceptably low complication rates (equal to or less than surgical rates), and a pseudocyst recurrence rate of 10-20%. 51 Endoscopic therapy has also been shown to be effective in the management of partial 52 and complete pancreatic duct disruptions, 56 pancreatocutaneous fistulas, pancreatic ascites, and pancreatic-pleural effusions. 57 The role of endosonography in the management of pseudocysts is evolving. EUS may be used to help localize the cyst and determine whether any intervening vascular structures are present in the gut wall at the planned site of puncture, mark the spot of safe puncture, (although its utility in reducing the frequency of bleeding has not been resolved), determine the cyst to lumen distance, and assess the cyst contents. Endoscopic drainage may be avoided if EUS detects large amounts of necrotic debris or prominent septae in the cyst. With the development of larger channel linear array echoendoscopes, EUSguided drainage of pseudocysts will be done more commonly and will expand the indications for endoscopic drainage (e.g., to include pseudocysts causing a mild or no bulge) Biliary Obstruction in Chronic Pancreatitis Distal common bile duct strictures have been reported to occur in 2.7 to 45.6% of patients with chronic pancreatitis. Such strictures are a result of a fibrotic inflammatory restriction or compression VOLUME 52, NO. 6, 2000 GASTROINTESTINAL ENDOSCOPY 845

4 Author Title by a pseudocyst. 60,61 Because long-standing biliary obstruction can lead to secondary biliary cirrhosis or recurrent cholangitis, biliary decompression has been recommended. Surgical therapy has been the traditional approach. However, based on the excellent outcome of endoscopic biliary stenting for postoperative strictures, including a low morbidity rate, evaluation of similar techniques for bile duct strictures complicating chronic pancreatitis has been undertaken It is clear that polyethylene (plastic) biliary stents are a useful alternative to surgery for the short-term treatment of chronic pancreatitisinduced common bile duct strictures complicated by cholestasis, jaundice, and cholangitis. Such therapy should also be considered for high-risk surgical patients. However, because resolution of the stricture is uncommon (12-28%), the long-term efficacy of this treatment is much less satisfactory. At present, operative intervention appears to be a better long-term solution for this problem in average risk patients. Limited data suggest that expandable stents may play a role in the management of these strictures. 64 However, more data on the long-term outcome, preferably in controlled trials, are necessary before metallic stents can be advocated for this indication. Conclusion Endoscopic therapy of chronic pancreatitis is gaining wider application. Selection of appropriate candidates for the various treatment methods appears to be important for optimal results of therapy. Endoscopic management should be considered as one management option along with medical, percutaneous, and surgical treatments. Firm guidelines for the application of endoscopic therapy is difficult because there are no controlled studies, follow-up in most series is brief, and there are no studies comparing endoscopic and surgical therapy. 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6 Author Title ic pancreatitis with metal mesh self expandable stents. Gut 1994;35: Prepared by: Standards of Practice Committee Glenn M. Eisen, MD, Chair Robynne Chutkan, MD Jay L. Goldstein, MD Bret T. Petersen, MD Michael E. Ryan, MD Stuart Sherman, MD John J. Vargo, II, MD Richard A. Wright, MD Harvey S. Young, MD Marc F. Catalano, MD Frederick Dentsman, MD C. Daniel Smith, MD Virginia Walter, MS, RN, BS, CGRN 848 GASTROINTESTINAL ENDOSCOPY VOLUME 52, NO. 6, 2000