Fistula formation between a pancreatic pseudocyst and the biliary tree Introduction: Fistula formation between a pancreatic pseudocyst and the biliary tree is uncommon. Clinical case: We report a 71 years old female who developed a pancreatic pseudocyst secondary to a biliary acute pancreatitis. After eight weeks of evolution, the patient was operated due to the size of the pseudocyst and the presence of symptoms. During the operation, a fistula between the cyst and the biliary tree was found. It was successfully excluded performing a choledochostomy with a Kehr tube and pseudocyst drainage. The patient had an uneventful postoperative evolution and imaging studies at the moment of discharge, one month after the operation, did not show a residual cavity.