A pathological diagnosis was also made for all 27 patients based on surgical or biopsied specimens. All 27 patients had serum IgG4 concentrations within the normal range. All ERCP and endoscopic biopsies were carried out during the hospital stay. ERCP was carried out using a duodenoscope (JF-240, TJF-240, TJF-260V; Olympus

Medical Systems Corp., Tokyo, Japan). A 1.7-mm-diameter cannula (PR-V416Q; LY2157299 Olympus Medical Systems) was inserted into the main pancreatic duct and bile ducts, cholangiopancreatograms were obtained and the location of stricture was carefully studied. After documenting the stricture, a 0.035-inch hydrophilic guidewire Palbociclib (stiff-type Jagwire; Boston Scientific Japan, Tokyo, Japan) was advanced to the tip of the cannula, through the stricture and into the bile duct beyond the stricture. After carrying out the ERCP, all

patients underwent endoscopic biopsies using side-opening biopsy forceps (FB-45Q-1; Olympus) from Vater’s ampulla and the common bile duct in the same session. The guidewire was left in place and the biliary biopsy forceps were passed along the guidewire and into the bile duct. Bile duct biopsies were taken from the lower and intrapancreatic bile ducts or other stenotic portions in IgG4-SC patients, the extrahepatic bile duct in PSC patients and the involved bile duct in pancreatobiliary malignancy patients under fluoroscopic guidance. In all 29 IgG4-SC patients, biopsies were obtained from Vater’s ampulla and the common bile duct before corticosteroid therapy. After carrying out the bile duct biopsies, Vater’s ampulla biopsies were taken from the

orifice of the common bile duct near the guidewire, but were not taken near the orifice of the pancreatic duct to avoid acute pancreatitis resulting from edema and reduced ductal flow. The procedures were finished without placing a pancreatic stent. All endoscopic procedures were carried out by the same experienced endoscopist (HK) while the patient was under conscious sedation with intravenous Baricitinib pethidine hydrochloride and diazepam. After the ERCP-related procedures, 50 000 units of ulinastatin were drip-infused twice (day of surgery and the next morning) over a period of 1–2 h. Antibiotics were drip-infused twice (once after the ERCP-related procedures and once the next morning) through a side tube. Histological examination was carried out by a pathologist (YZ) blinded to clinical information. The biopsied specimens were fixed in neutral formalin and embedded in paraffin. Sections (4 µm) were cut from each paraffin block and stained with hematoxylin–eosin or examined by immunohistochemistry.