Severity of Post-ERCP Pancreatitis Directly Proportional to the Invasiveness of Endoscopic Intervention: A Pilot Study in a Canine Model

Background and study aims: Pancreatitis complicates 1%-22% of endoscopic retrograde cholangiopancreatography procedures. The study aims were to develop a reproducible animal model of post-ERCP pancreatitis (PEP), and investigate the impact of endoscopic technique on severity of PEP. Patients and methods: ERCP was carried out in six male hound dogs. Pancreatitis was induced by one of three escalating methods: 1) pancreatic acinarization with 20-30 mL of contrast; 2) acinarization + ductal balloon occlusion + sphincterotomy; 3) acinarization + intraductal synthetic bile injection + ductal balloon occlusion + sphincterotomy. Dogs 5 and 6 received a pancreatic stent. Necropsy was performed on postoperative day 5. All pancreatic specimens were graded by two blinded pathologists according to a validated scoring system. All dogs were compared with three control dogs. Results: Dogs 1-4 developed clinical pancreatitis and hyperamylasemia (11736 vs. 722 U/L, P=0.02). Total injury scores were significantly elevated compared with controls (6.85 vs. 1.06, P= 0.004). There was significant increase in acinar cell necrosis (0.86 vs. 0.06, P= < 0.001), and all other categories (except fibrosis) demonstrated elevated injury scores. Dogs 5 and 6 developed clinical pancreatitis without significant hyperamylasemia; total injury scores were elevated compared with controls (4.83 vs. 1.06, P= 0.01), but lower than in Dogs 1-4 (4.83 vs. 6.85, P= 0.25). There was escalating severity of pancreatic injury from Dogs 1 to 4 correlating with the method of endoscopic injury used. Conclusion: Severity of PEP is directly proportional to invasiveness of endoscopic intervention. Pancreatic acinarization, even without balloon occlusion and sphincterotomy, can be used as a reliable animal model for future studies investigating therapy and prevention of disease.