A 56-year-old female presents at the emergency department after a sudden-onset middle and upper abdominal pain for 12 hours，and was diagnosed of acute pancreatitis after examination. Which of the following statements is FALSE about acute pancreatitis?
A: About 50% are secondary to bile duct diseases.
B: Bacterial infection is not a major cause of onset.
C: Further diagnostic evidence is needed if hematuria amylase is not high.