Is sphincter of Oddi manometry a risk factor for pancreatitis? A different view

Studies suggest a causal relationship between sphincter of Oddi manometry (SOM) and acute pancreatitis, presumably due to water instillation in the ductal system. In this article, critical analysis of the existing studies attributes the high risk of acute pancreatitis with SOM to "association due to confounding" rather than to "causation." This conclusion is based on two pieces of evidence: The first is lack of biologic plausibility: Biologic evidence is lacking to support the hypothesis that water instillation during SOM can induce acute pancreatitis. The second is confounding evidence: Manometric studies show considerable variation in the risk of post-procedure pancreatitis (4% to 30%), which suggests that other important factors besides SOM influence the adverse outcome. These studies did not control for other variables, which are well known to predispose to pancreatitis and therefore may act as confounding factors. Two studies that assessed the independent role of SOM in causation of acute pancreatitis showed that SOM is not an independent predictor of acute pancreatitis. It is the underlying disorder sphincter of Oddi dysfunction, and not the "SOM" procedure, that predisposes patients to post-procedure acute pancreatitis.