Background: Endoscopic retrograde cholangiopancreatography (ERCP) has a high risk of pancreatitis although the underlying mechanisms are unclear. Transient receptor potential vanilloid 1 (TRPV1) is a cation channel expressed on C and Aδ fibers of primary sensory neurons and is activated by low pH. TRPV1 activation causes release of inflammatory mediators that produce edema and neutrophil infiltration. We previously demonstrated that neurogenic factors contribute to the pathogenesis of pancreatitis. Resiniferatoxin (RTX) is a TRPV1 agonist that, in high doses, destroys C and Aδ fibers. When we discovered that the pH of radio-opaque contrast solutions used for ERCP was 6.9, we hypothesized that low pH may contribute to the development of contrast-induced pancreatitis via activation of TRPV1.
Methods: Rats underwent equal pressure pancreatic ductal injection of contrast solutions at varying pH with or without RTX.
Results: Contrast solution (pH 6.9) injected into the pancreatic duct caused a significant increase in pancreatic edema, serum amylase, neutrophil infiltration, and histological damage. Solutions of pH 7.3 injected at equal pressure caused little damage. Pancreatitis severity was significantly increased by injection of solutions at pH 6.0. To determine if the effects of low pH were mediated by TRPV1, RTX was added to the contrast solutions. At pH levels of 6.0 and 6.9, RTX significantly reduced pancreatitis severity.
Conclusions: Low pH contrast solutions contribute to the development of pancreatitis through a TRPV1-dependent mechanism. It is possible that increasing the pH of contrast solution and/or adding an agent that inhibits primary sensory nerve activation may reduce the risk of post-ERCP pancreatitis.