Transient physiological changes occur in pancreatic blood flow secondary to increased demands such as eating. Changes can also be induced pharmacologically using pancreatic stimulating agents, such as secretin. This naturally occuring peptide is produced within the S cells of the proximal small bowel mucosa. It causes an increase in bicarbonate secretion by the duct cells of the pancreas and biliary tract via an oxygen dependant cyclic AMP mediated pathway. Secretin has been used previously to assess alterations in blood flow and is used clinically in the assessment of sphincter of Oddi dysfunction in conjunction with magnetic resonance cholangiopancreatography.