pancreaticobiliary complications following various pancreatic and hepatic operations were previously treated conventionally with surgery , but reoperations in such patients who are critically ill are often difficult because of inflammation , infections , and adhesions . although endoscopic therapy can help avoid huge amounts of reoperation , it tends to be technically challenging especially in cases of altered gastrointestinal ( gi ) anatomy . the systematic approach for the use of endoscopic retrograde cholangiopancreatography ( ercp ) or endoscopic ultrasonography ( eus ) as a treatment modality for treatment of pancreaticobiliary adverse events after surgery has not been clearly established because of the rarity of data . this review focused on challenges encountered by endoscopists in managing pancreaticobiliary complications in surgically altered gi anatomy based on the published articles of highly experienced groups . pancreatic leaks can occur in about 20% of cases following whipple surgery ( pancreaticoduodenectomy ) , whereas the pancreatic fistula rate was 5% for chronic pancreatitis , 12% for pancreatic cancer , 15% for ampullary cancer , and 33% for bile duct cancer in a large case review of 2,664 patients who underwent pancreaticoduodenectomy . endoscopy plays a limited role in the management of acute postoperative adverse events ( pancreatic duct [ pd ] leak , bile leak , and pancreatic fistula ) following whipple surgery . pancreatic leaks can be managed by percutaneous drainage , administration of octreotide , and intravenous hyperalimentation . however , endoscopy plays a significant role in the management of retained surgically placed pancreatic stents , recurrence of malignancy , and delayed pancreaticobiliary ( choledochojejunostomy and pancreaticojejunostomy ) strictures and/or stones . roux - en - y hepaticojejunostomy is performed with various indications , including recurrent biliary stones , benign distal biliary stricture , cholangiocarcinoma , choledochal cyst , and liver transplantation . post - liver transplantation biliary adverse events occur in up to 20% of patients and are important causes of early and late postoperative morbidity and mortality . the most common biliary adverse events are strictures , leaks , stones , and sphincter of oddi dysfunction . endoscopic management of these adverse events is greatly influenced by the type of biliary reconstruction during liver transplantation . in cases of anastomotic biliary strictures that occur in about 5%10% of liver transplantation recipients within 1 year after surgery , endoscopists frequently come across patients with postoperative altered anatomy such as in billroth ii gastrectomy , pancreaticoduodenectomy ( classic or pylorus - preserving pancreaticoduodenectomy ) , roux - en - y gastric bypass ( rygb ) , roux - en - y hepaticojejunostomy , and roux - en - y choledochojejunostomy . challenges encountered by endoscopists in these altered gi anatomy are usually due to difficulty in ( 1 ) identifying the pancreaticobiliary enteral limb ; ( 2 ) reaching and identifying the major papilla or pancreaticoenteric and/or bilioenteric anastomoses ; ( 3 ) selective cannulation of the bile or pd from an altered orientation ; and ( 4 ) performing therapeutic interventions with devices designed for standard ercp or possibly with a forward - viewing endoscope that is not equipped with an elevator . to correctly identify the enteral limbs , understanding the postoperative anatomic change and length of surgically created pancreaticobiliary limb , the adequate endoscopes and suitable accessories can be chosen to successfully accomplish the aim of the endoscopic procedures . in patients with relatively short afferent limbs , ercp may be performed with a duodenoscope , forward - viewing gastroscope , or colonoscope ( adult and pediatric ) . however , the success rate in accessing the pancreatic anastomosis is suboptimal with a standard duodenoscope . absence of an elevator in a colonoscope makes it challenging to maneuver the accessories and accomplish therapeutic interventions . a prototype oblique - viewing endoscope with an elevator has been used to circumvent this drawback . limited but increasing amount of data are available about overtube - assisted enteroscopy ercp with a single - balloon enteroscope ( sbe )   or double - balloon enteroscope ( dbe )   to get technical success in case of failure to reach the anastomotic site with standard endoscopes . other endoscopic options to access the biliary tree is combined use of interventional radiology and ercp in which the placement of a stent or guide wire by an interventional radiologist was followed by subsequent endoscopic management . percutaneous approach to reach pancreaticojejunal anastomotic strictures has been used at tertiary centers when pancreatic anastomosis can not be identified or accessed endoscopically . this combined approach is preceded by a detailed cross - sectional imaging such as computed tomography ( ct ) or magnetic resonance cholangiopancreatography ( mrcp ) . another interesting technique for failed identification or access of pancreatic anastomosis is the combined eus and ercp technique . indications of eus - guided pd drainage include chronic pancreatitis - induced strictures and stones , disconnected pds , inaccessible ampulla , and postsurgical altered anatomy . pancreatic ductal access and therapeutic intervention can be accomplished with a linear echoendoscope in many reports from expert centers [ 14 - 20 ] . according to a report on eus - guided pd drainage performed when retrograde access to the pd was technically unsuccessful because most of the patients underwent pancreatoduodenectomy , 64.7% of rendezvous procedures were successfully performed . although choledochocholedochostomy is the preferred procedure , roux - en - y reconstruction ( end - to - side choledochojejunostomy or hepaticojejunostomy ) is performed in some cases of liver transplantation . roux - en - y reconstruction is often used in children and adults with bile duct disease such as sclerosing cholangitis . hepaticojejunostomy is created with transection of the mid bile duct in most of the cases and if complication occurs in those situations , ercp will not be possible with a standard duodenoscope . the only way to view the bilioenteric anastomosis in these cases is by passing a long endoscope ( adult and pediatric colonoscope , sbe , or dbe ) through the proximal jejunum and up the afferent jejunal limb . variable stiffness pediatric colonoscope is the ideal endoscope , with which searching for the anastomosis may take some experience , as it is frequently hidden behind a sharp turn or recessed fold . in a multicenter retrospective review of ercp in postoperative patients , 12 patients who underwent roux - en - y hepaticojejunostomy had 100% ercp success rate with a pediatric colonoscope . a thorough understanding of a surgically altered anatomy is essential to minimize adverse events and to enhance the chance of a successful outcome in these cases . in patients with relatively short afferent limbs , ercp may be performed with a duodenoscope , forward - viewing gastroscope , or colonoscope ( adult and pediatric ) . however , the success rate in accessing the pancreatic anastomosis is suboptimal with a standard duodenoscope . absence of an elevator in a colonoscope makes it challenging to maneuver the accessories and accomplish therapeutic interventions . a prototype oblique - viewing endoscope with an elevator has been used to circumvent this drawback . limited but increasing amount of data are available about overtube - assisted enteroscopy ercp with a single - balloon enteroscope ( sbe )   or double - balloon enteroscope ( dbe )   to get technical success in case of failure to reach the anastomotic site with standard endoscopes . other endoscopic options to access the biliary tree is combined use of interventional radiology and ercp in which the placement of a stent or guide wire by an interventional radiologist was followed by subsequent endoscopic management . percutaneous approach to reach pancreaticojejunal anastomotic strictures has been used at tertiary centers when pancreatic anastomosis can not be identified or accessed endoscopically . this combined approach is preceded by a detailed cross - sectional imaging such as computed tomography ( ct ) or magnetic resonance cholangiopancreatography ( mrcp ) . another interesting technique for failed identification or access of pancreatic anastomosis is the combined eus and ercp technique . indications of eus - guided pd drainage include chronic pancreatitis - induced strictures and stones , disconnected pds , inaccessible ampulla , and postsurgical altered anatomy . pancreatic ductal access and therapeutic intervention can be accomplished with a linear echoendoscope in many reports from expert centers [ 14 - 20 ] . according to a report on eus - guided pd drainage performed when retrograde access to the pd was technically unsuccessful because most of the patients underwent pancreatoduodenectomy , 64.7% of rendezvous procedures were successfully performed . although choledochocholedochostomy is the preferred procedure , roux - en - y reconstruction ( end - to - side choledochojejunostomy or hepaticojejunostomy ) is performed in some cases of liver transplantation . roux - en - y reconstruction is often used in children and adults with bile duct disease such as sclerosing cholangitis . hepaticojejunostomy is created with transection of the mid bile duct in most of the cases and if complication occurs in those situations , ercp will not be possible with a standard duodenoscope . the only way to view the bilioenteric anastomosis in these cases is by passing a long endoscope ( adult and pediatric colonoscope , sbe , or dbe ) through the proximal jejunum and up the afferent jejunal limb . variable stiffness pediatric colonoscope is the ideal endoscope , with which searching for the anastomosis may take some experience , as it is frequently hidden behind a sharp turn or recessed fold . in a multicenter retrospective review of ercp in postoperative patients , 12 patients who underwent roux - en - y hepaticojejunostomy had 100% ercp success rate with a pediatric colonoscope . a thorough understanding of a surgically altered anatomy is essential to minimize adverse events and to enhance the chance of a successful outcome in these cases . ercp and/or eus are technically the most difficult procedure in endoscopic practice , and the most difficult situation is in cases of postoperative complications of an altered gi anatomy . careful preprocedural planning is mandatory in all cases to get successful outcomes . before performing the procedure , understanding the postsurgical anatomy is important , and sometimes , checking operation reports , reviewing available radiologic images , and discussing with the surgeon to get clear information are required in complicated cases . choice of the endoscope can only be made according to the endoscopist s understanding of the anatomic change and expertise . a clear cap can be used to help in the visualization of pancreatic and/or biliary anastomoses in patients with a whipple resection . effort to minimize loop formation by applying external abdominal pressure or changing the patient s position , and maneuvers to straighten the endoscope are helpful to get the best outcomes . more detailed reviews about ercp in post - gastrectomy and bilioenteric anastomosis , eus in altered gi anatomy , and percutaneous transhepatic cholangioscopy in bilioenteric anastomotic strictures are included in the focused review series section of this issue of clinical endoscopy . owing to the relative safety and effectiveness for diagnosis and therapy for postoperative pancreaticobiliary complication with altered gi anatomy , endoscopic management would progressively replace reoperation and might become the treatment of choice in the near future . careful preprocedural planning , including cautious review of operation reports and radiological images for complete understanding of postsurgical anatomic alteration , and multidisciplinary approach with close collaboration between gastroenterologists , surgeons , and interventional radiologist are needed for successful outcomes .
pancreaticobiliary complications following various surgical procedures , including liver transplantation , are not uncommon and are important causes of morbidity and mortality . 
 therapeutic endoscopy plays a substantial role in these patients and can help to avoid the need for reoperation . 
 however , the endoscopic approach in patients with surgically altered gastrointestinal ( gi ) anatomy is technically challenging because of the difficulty in entering the enteral limb to reach the target orifice to manage pancreaticobiliary complications . 
 additional procedural complexity is due to the need of special devices and accessories to obtain successful cannulation and absence of an elevator in forward - viewing endoscopes , which is frequently used in this situation . 
 once bilioenteric anastomosis is reached , the technical success rates achieved in expert hands approach those of patients with intact gi anatomy . 
 the success of endoscopic therapy in patients with surgically altered gi anatomy depends on multiple factors , including the expertise of the endoscopist , understanding of postoperative anatomic changes , and the availability of suitable scopes and accessories for endoscopic management . in this issue of clinical endoscopy , the focused review series deals with pancreatobiliary endoscopy in altered gi anatomy such as bilioenteric anastomosis and post - gastrectomy .