a 75-year - old man was admitted for treatment of acute alcoholic hepatitis . with enhanced computed tomography ( ct ) , endoscopic ultrasound ( eus ) showed a multiple - cystic lesion with mural nodule in the tail of the pancreas and a diameter of 17  mm . to obtain pancreatic juice for cytopathologic examination cannulation of the pancreatic duct was difficult and took more than 30 minutes ( no cannulation into the bile duct during the procedure ) . we did not perform intraductal ultrasound and brushing because the cystic lesion was located on the end of the pancreas close to the splenic hilum . subsequently , an indwelling 5-fr enpd - tube was inserted in the pancreatic duct ( fig .  1 ) . the enpd tube had 4 side holes within 35  mm of its distal end . there was no obvious finding to suggest the presence of pancreaticobiliary maljunction based on magnetic resonance cholangiopancreatography ( mrcp ) prior to ercp ( fig .  2 ) . however , backflow of a small amount of contrast medium into the bile duct was present when a generous amount of contrast medium was injected into the pancreatic duct ( fig .  1 , no ae was noted during the procedure . 
 a 5-fr endoscopic nasopancreatic drainage tube indwelling in the pancreatic duct . there was no obvious finding suggestive of the presence of pancreaticobiliary maljunction , but a small amount of contrast medium flew back into the bile duct ( arrow ) . 
 on magnetic resonance cholangiopancreatography , there were no obvious findings suggestive of the presence of pancreaticobiliary maljunction . although about 200  ml of pancreatic fluid had been drained and the enpd tube was removed 22 hours after the ercp , the level of pain kept increasing . contrast - enhanced ct showed a swollen gallbladder with an apparent thickening of the wall without evidence of biliary tract dilatation . in addition , massive ascites that had not been seen before ercp were identified ( fig .  3 ) . ascitic fluid was orange - colored and cloudy , and bilirubin and amylase concentrations ( 38.9  mg / dl and 4325 iu / l , normal limit is 1.0  mg / dl and 125  iu / l ) far exceeded the corresponding values measured in the blood on the same day ( 0.6  mg / dl , 119 perforation of the duodenum but not the biliary tree was initially suspected , as both amylase and bilirubin levels in the ascites were high . contrast - enhanced computed tomography ( ct ) at 30 hours post - endoscopic retrograde cholangiopancreatography . subsequently , exploratory laparotomy was performed . despite substantial bile in the peritoneal cavity , there was no evidence of duodenal perforation . the contents of the gallbladder were aspirated and its bilirubin and amylase levels were determined . therefore , acute cholecystitis with perforation due to acute pancreatobiliary reflux was diagnosed , and cholecystectomy was performed . pathologic examination revealed that inflammatory cells had infiltrated throughout all layers , and abscess formation and necrosis with perforation were found in the subserosal layer ( fig . no finding , such as hyperplastic change of gallbladder mucosa , was made that was suggestive of pancreaticobiliary maljunction and there were no gallbladder stones or tumor . the postoperative course was uneventful and the patient was discharged 9 days after surgery . the red arrow is the site of a puncture made by the surgeon to aspirate the contents of the gallbladder . b microscopic examination at the site of perforation showed invasion of inflammatory cells throughout all layers and abscess formation and necrosis in the subserosal layer . 2 reported that thrombosis in the intramural vessels appeared to be related to the events leading to ipgb . in contrast , a few reports have suggested that pancreatobiliary maljunction may contribute to its etiology 1 
 3 . nevertheless , it has been thought that pancreatobiliary reflux could result in several of various pathologic conditions in the biliary system , including acute cholecystitis , and pancreaticobiliary maljunction was not a necessary prerequisite 4 . acute cholecystitis generally is well known as a cause of ipgb 5 . in our case , however , there was no stone or tumor that could cause the cholecystitis in the biliary tree . in this case , acute cholecystitis and perforation occurred after insertion of the indwelling enpd - tube , thus it is believed that this pathologic condition occurred as an ae related to the ercp and insertion of the indwelling enpd - tube . pancreatobiliary reflux was highly implicated in the ipgb based on the high amylase concentration in the gallbladder contents 3 . however , in our case , pancreatobiliary maljunction was not identified on mrcp or ercp . past literature suggests that pancreatobiliary reflux can occur in individuals without pancreaticobiliary maljunction 6 
 7 
 8 . in particular , pancreatobiliary reflux has been frequently observed in individuals with a relatively long common channel 9 , and in our case , it was observed on ercp images . in fact , a small amount of contrast medium injected into the pancreatic duct back flowed into the bile duct , although mrcp did not indicate any pancreatobiliary maljunction . thus , it was speculated that pancreatic fluid could easily flow into the bile duct due to the indwelling enpd tube , which would eliminate space between the tube and the common channel . consequently , the concentration of pancreatic enzymes in the biliary tree rapidly increased and pooled in the gallbladder after insertion of the indwelling enpd tube , potentially causing acute cholecystitis , and subsequently gallbladder perforation . although enpd insertion is common in japan , it is hard to explain why ipgb has not been observed in many other cases . our patient might have a tendency to easily develop pancreatobiliary reflux because of the anatomy of the long common channel . in conclusion , our case supports the suggestion that pancreatobiliary reflux is an important cause of ipgb . in addition , ipgb also should be recognized as a possible ae of pancreatic stent insertion , especially in patients who have a long common channel .
background and study aims : endoscopic retrograde pancreatocholangiography ( ercp ) is associated with many types of adverse events ( aes ) but idiopathic perforation of the gallbladder ( ipgb ) is very rare . 
 pancreatobiliary reflux is one of the factors involved with occurrence of ipgb 1 . here 
 we present a case of acalculous gallbladder perforation as an ae following the insertion of an indwelling endoscopic nasal pancreatic drainage ( enpd ) tube ( a pancreatic stent ) to obtain pancreatic fluid . in this case , 
 acute pancreatobiliary reflux might have been caused by the insertion of the enpd - tube .